SPEEDWAY Mini Bike Information Chronological Guide.|
I buy and collect Speedway minibikes.
Overall Speedway History.
John Morrow "Frog" is the gentlemen kneeling on the right with glasses. Mickey Rupp is
standing behind him with the hat. The man to the left kneeling is John
Hale, owner of Hale's Harley Davidson.
skip to repair info
So what made Speedway mini bikes so interesting? Well from the start,
their bikes were high quality. No Speedway had less than a 10" wheels.
They mostly used a #40 motorcycle style chain. Tecumseh engines were stock,
and most bikes had 20 degree mounted motors.
Also nearly all models used an in-house designed "DynaTorque 400" torque converter
powered through a jackshaft.
Speedway was the first to introduce hydraulic telescopic front forks
(something most other manufacturers did in the next year, 1971.)
These features were not totally unique for 1970, but it was all a good thing, and put
them in an upper class of mini bikes. Were Speedways better than say Rupps?
Well they were certainly trying to be that. But personally, I'm not sure
the 10" wheel models achieved that goal. Speedways certainly are much rarer
than a Rupp though, and a bit different. For this reason there some people
that have latched onto the brand.
1970 Speedway Mini Bikes.
But what made Speedway really interesting, is a couple models that
weren't necessarily in their catalogs, and that were very low production. These included
some bikes that used 2-cycle Sachs motors.
The 1970 Speedway catalog
showed their catalog models utilized some standard things.
For example, the Tecumseh engine was standard. And for 1970
the 20 degree mounted Tecumseh motors were white (not black) with flag logo, and used a
diaphragm carb. They utilized a Taylor minibike exhaust (a
standard Tecumseh minibike exhaust), but added a chrome 3" wide extension on the back of the Taylor. It gave
a nice custom look. The gas tank was unique to Speedway. In 1970 the tank is known as
a "peanut" tank. It's two symmetrical halves put together with a center attachment strip.
This tank was also used for the clutch cover! Just look at the pictures, and you can
see that the clutch cover was one half of the gas tank. Speedway used this clutch cover
on all their models (with some minor mods) with Tecumseh engines, and for all years.
Also the rear section behind the seat "kicks up".
And the 1970 Speedway models used disc brakes for all positions and all models
(except the Stinger, which had a foot scrub brake.)
The serial number was on a chrome foil sticker with black lettering,
installed on the metal just behind the fork attachment point.
This serial number position was a standard thing for all Speedways.
But they only used the foil sticker in 1970 (serial numbers mid 10,000 and less.)
Frame differences in 1970 versus later 10" wheel bikes. The gas tank mount
was obviously way different, but the entire top tube system was changed in 1971
to a cleaner design. The top frame is 1970, the bottom frame is 1971.
The 10" wheel frame used in 1970 by Speedway was different than their 1971 and later models.
If you look at the picture above, you can see the difference (top frame is 1970,
bottom frame 1971.) Not only did the mount for the gas tank change, but the
top tube is actually two tubes that extend all the way behind the seat
on the 1970 frame. The 1971 and later 10" wheel frames
used a single U-shaped top tube, that welded to the oval seat tube. Also the
head plate is longer on the 1971 frame, because cracks easily formed where the
lower tubes met the head plate on 1970 frames. Lastly the "kick up" behind the seat
was taller on 1970 frames. Because of the
frame changes, a 1970 frame can only hold a 1970 style gas tank. Later 1971 to
1974 frames for 10" wheel bikes are largely interchangeable (within models.)
1970 Speedway Scarab.
The main two 1970 Speedway models included the Scorpion and the Scarab. Both had a 20 degree mounted
white 4hp HS40 (172cc) Tecumseh engine, DynaTorque 400 Speedway torque converter, front/rear suspension,
and front/rear disc brakes. Rear 3.50x10" motocross tire, front 3.50x10" trials tire (though the front tire is
sometimes motocross style on the Scarab, Speedway was a bit inconsistent on this feature.)
The main difference between the two models was lights (Scorpion), and no lights (Scarab).
1970 Speedway Scorpion - lights and rear suspension (motor newer and not original on this bike).
The other two main 1970 Speedway models were the Shark and Shrike. The difference between the
two is again lights (Shark), versus no lights (Shrike). Also the Shark and Shrike had
no rear suspension (hard tail) and no front brake (rear disc brake). Rear motocross tire, front trials tire
(though the rear tire is sometimes trail style, Speedway was a bit inconsistent on this feature.)
The white Tecumseh engine on these two models was smaller
too at 3hp (127cc). The Shrike intially did not use the DynaTorque 400 Speedway torque converter
either (the Shark does have a TC) - the Shrike had a standard centrifugal clutch and no jackshaft.
This changed quickly though for the Shrike, and it ended up with a torque converter and jackshaft
sometime during 1970.
Also in the catalog was the Stinger, the low-end model. It had no torque converter (centrifugal clutch)
and no peanut gas tank (though it still used the 10" mag wheels with 3.00x10" trials tires).
Handle bars were not fold down either. Used a flat mount white 2.5hp Tecumseh motor. The clutch
cover was still a gas tank half, but it did not have the cutouts for the torque converter belt
(since there was no torque converter.) It also used a #35 chain and had a rear scrub brake.
1970 Speedway Shark - lights but no rear suspension.
A late 1970 model not in the catalog was the Superstar. Very low production,
it appears to be their introduction to the mini bike mass market, as it was
intended to be sold by JC Penney. But the deal never materialized, so the
few that Speedway made were sold by their dealers.
It was essentially the same as the other 1970 Speedway catalog models, with a few exceptions. The
biggest difference is the Speedway Superstar used a 1968/1969 Rupp gas tank.
Apparently when Rupp changed gas tank designs in 1970, there was a fair
number of left-over earlier style tanks. And Speedway took advantage of that
and used it on their Superstar model. Also the Superstar had a luggage
rack behind the seat and a mud guard in front of the engine.
And a slightly different seat design. But other than
that, the Superstar was pretty much the same as a 1970 Speedway Scarab.
The original Tecumseh engine was black on this model.
1970 Speedway Superstar. Notice the Rupp gas tank and luggage rack.
Serial number for a 1970 Speedway Superstar. Notice the top edge that should
say "Speedway" but was cut off with scisors!
Speedway was sensitive to the influx of the Honda CT70 mini bikes. They were smart enough
to realize that Honda (who was selling their mini bikes for less than cost,
to gain a foot hold in the U.S. market) would be tough to battle. Check out the
ad below where Speedway compares itself directly to a Honda CT70.
1970 Speedway ad versus Honda.
There is one other late 1970 model that should be noted. It is the rarest of the Speedways,
and probably considered to be the best Speedway made. It's the late 1970 Speedway Silver Shadow.
Really just a Speedway Scorpion painted silver. But they added a 125cc Sachs 2-cycle motor.
And instead of lights (like a Scorpion), installed a front number plate (opposed to a headlight.)
Talk about over-powered, this little beast is said to go 80 mph! They did not make many of
1970 Speedway Silver Shadow restored.
Note the 1970 Speedway Silver Shadow (and the Superstar) were not shown in the 1970 Speedway catalog.
Speedway did have a habit of doing this - making some low production models or year-end models
that weren't in the catalog.
1970 Speedway Shrike serial number.
The serial number tag used on 1970 models is a chrome foil sticker with black lettering.
Positioned on the top of the frame top behind the triple tree. The first two digits are "70-"
to signify the year. This was the only year they used this style serial number tag and format.
From 1971 to 1973 the position of the serial number stayed the same, but they moved to a
stamped-in style number, opposed to a foil sticker. In 1973 the serial number moved to
a metal tag, riveted to the frame.
1970 Speedway Scorpion serial number.
Note in the 1970 Scorpion serial number above, they forgot to put the
actual number (the "70-" just denotes the year). I guess this happens
when you're a brand new company!
1970 and 1971 Speedway 10" tires that actually said "Speedway". The "Universal"
tire is the trials style and the "Motocross" tire is obviously motocross style.
By 1972 the Speedway seemed to run out of these custom branded tires,
and used trials style that just said "Carlisle" as the brand for 10" wheel bikes.
1971 Speedway Mini Bikes.
The 1971 Speedway catalog
shows a lot of the same models as the 1970 catalog, but with a new gas tank style. The clutch cover is still
the same (half of the 1970 Speedway gas tank), but the 1971 gas tank is now more slick and modern.
The Scorpion, Scarab, Shark have not changed much. The Shrike is now a torque converter bike
with a jackshaft. Other than the gas tank change, now all models are
using a drum brake for the rear wheel. The Scarab had
motocross tires front and rear (Scorpion has 3.50x10" motocross in rear and a street trials 3.50x10" tire up front.)
The Shrike and Shark used 3.50x10" tires (either trials or motocross style), but sometimes 3.00x10" is also seen.
1970 Speedway wheel (left), versus 1971-1974 Speedway 10" wheel (right). Notice the change of the wheel cutouts
from the rounded triangle (1970) to the kidney bean shape (1971-1974.)
Also 1971 was the last year for
the tires to say "Speedway" on the sidewalls (either "Speedway Motocross" or "Speedway Universal" for the trials tires.)
The Tecumseh engines used are now black (no longer white,
except on the low-level Stinger model). Also the Tecumseh diaphragm carb is replaced
with a standard float bowl variety, and the intake manifold is angled (much like Rupp.)
The Speedway designed DynaTorque 400 torque converter
was still used. The "kick up" on the rear end of the seat is still there too (though slightly less tall.) And in
late 1971 Speedway added a piece of sheet metal across the inside front of the tube kickup
(I guess to support the seat.)
Drum brakes are also standard on 1971 models (disc brakes were largely discontinued, except for some
front brake applications.) The 10" wheels changed too. The cutouts for the "spoke" area are now
kidney bean shaped (instead of rounded triangles.)
Serial numbers for 1971 models are generally in the high 10,000 to 20,000 range.
1971 Speedway Scorpion.
Speaking of the DynaTorque 400 torque converter, the driven side is usually 5" (not today's
standard of 6"). Also it was a symmetrical type of torque converter. From what I have seen,
usually part (or all) of the original torque converters are missing on today's bikes. To deal
with this, I replace the original 5" driven unit with a 6" TAV20 Comet style symmetrical torque converter.
Likewise the driver gets replaced with a Comet symmetrical style too. This works very well, but some
modifications to the torque converter cutout need to be done to make it fit. Note you can not
use the TAV30 asymmetrical style torque converter on Speedways that originally had a symmetrical TC.
1971 Speedway Scarab, non-original carb, later style tank decal.
Something Speedway did in late 1971 was to make a "Shrike stage 2" model. This happened for
sure on the Shrike, not sure if the Scarab got this treatment too. The "stage 2" means
the torque converter driven increased from 5" to 6", and the Tecumseh went from 3hp to 4hp.
Late 1971 Speedway Shrike Stage 2.
Some new models appeared in the 1971 catalog. The Speedway Silver Shadow SST, with a 125cc Sachs engine,
is part of the catalog. It now has a rear fender 'tail' that looks a bit weird! There's also a Silver Shadow SSR
model, which is the same as the SST, but with lights (street legal.) Lastly there was also a "Black Shadow" Speedway
model too (not shown in the catalog.) It's basically a Silver Shadow with an 80cc Sach motor
and no flaring behind the seat.
On the 10" wheel bikes a metal adaptor plate was used on the frame to allow
attachment of the 2-cycle Sachs motor (red frame 1971, black frame 1972.)
1971 Speedway Black Shadow, wrong motor (should have an 80cc Sachs.) The 1971 Speedway Black Shadow was different
than the 1972 model (notice the kick up behind the seat.)
1971 Speedway Silver Shadow SSR (lights). Notice the difference from the 1970 model, with
the rear seat shoud tail.
But the big model is the yellow 1971 Speedway Super Spyder bike (aka the Super Bitch).
Again it uses the Sachs 125cc motor, but is much
larger with 16" spoked wheels. It's not street legal (no lights), and surprisingly came with trial tires
(opposed to motocross tires.) Unfortunately this model never went into production. But I hear a guy
in Ohio made a clone of the Super Spyder using various parts and information from the Speedway catalog.
1971 Speedway Super Bitch (Super Spyder). This bike was made from parts (not a 'real' Speedway,
because it didn't come out of the factory - but still pretty 'real' looking!)
Note that 1971 Speedway models with 10" wheels are much more common than their 1970 counterparts.
Actually 1970 models are hard to find - the 1971 models with 10" wheels seem to be much more plentiful.
Personally I like the 1971 Speedway 10" wheel models the best. They seem to be more "dialed in" than
the 1970 models. And in 1972 some things were removed from the 10" wheel bikes that make them seem less "cool."
1972 Speedway Mini Bikes.
The 1972 Speedway catalog
shows a pretty big change in the product line up.
The big change is the move to 14" wheel bikes. The Speedway Green Horn, Speedway Red Baron,
and Speedway Blue Angel are new to the line up. These are quite nice bikes, and handle great.
The 14" wheels are pretty awesome. The Green Horn has a Tecumseh HS50 five horsepower engine,
and lights. Remember 1972 is the first year for the Tecumseh HS50 motor, and Speedway put
it to good use on the Green Horn. The Red Baron is basically the same as a Green Horn
(lights), but uses a HS40 Tecumseh four horsepower motor. Likewise the Blue Angel also
has the HS40 engine, but no lights. Other than the color and lights/no lights and 4 or 5hp
engine, these three models are essentially the same. Also notice these models use a
different gas tank than the 10" wheel models.
The 1972 Speedway Black Shadow with an 80cc Sachs engine. Slightly different than
the 1971 version.
The 1972 to mid 1973 Speedway models were the last year to have the serial number stamped
into the frame (in front of the gas tank). So basically 1971 and 1972 and mid 1973 they
were stamped into the frame (1970 they had a silver sticker.) Then after mid 1973 they
used a riveted plate with the serial number. Also the 1972 models seemed to be generally
in the 20,000 to mid 30,000 number range.
1972 Speedway Green Horn, non-stock carb.
In 1972 the 10" wheel models are still there, with the Scorpion (lights) and Scarab (no lights)
being available. The Shrike and Sabre are still available (no rear suspension.)
Also the 10" frame models have a different rear end. Instead of the "kick up" at
the end of the seat, it is now just protruding with no kick up, a flat rear end
(which is handle for lifting the bike into a pickup truck.) The footpegs changed
too from a thin 3/16" thick mount and round peg, to a U shaped peg (and the Hunt Wilde plastic
cover could no longer be used.)
1972 Speedway Red Baron, non-stock carb.
1972 Speedway Blue Angel, non-stock carb.
Another 1972 Speedway Blue Angel, all original survivor with original HS40 engine.
Speedway does continue to use the Sachs motors on a few models too. The Speedway Black Shadow (10" wheels)
has a Sachs 80cc motor. The Speedway Widow Maker has 14" wheels and a Sachs 80cc motor. Neither of these
have lights. The Super Spyder has a Sachs 125cc motor and 16" whees and a 5-speed manual transmission.
All these Sachs motor based Speedways are pretty rare. The Speedway Widow Maker and Black Shadow come up
now and then. But the 1972 Speedway Super Spyder was never produced, at least in any numbers.
1972 Speedway Widow Maker with 80cc Sachs motor.
1972 Speedway Super Spyder with 125cc Sachs motor. Very few of these were made.
A change in torque converters happened in 1972. Speedway now used a Fairbank Morse driven unit.
Also Comet was used on some model in late 1972. Also in 1972 the torque converter driven unit
moved to 6" diameter (instead of 5") on most models. Also Betor shocks were now used instead of Sebac shocks.
And around mid 1972, some of the 14" wheel models had the sides of the gas tank are recessed,
as a place marker for the tank decal.
Below is an original 1972 Fairbanks Morse style Speedway torque converter, as used
on an original 1972 Speedway Blue angle. Also notice the clutch cover warning decal.
The rectangle decal is from 1972, the oval style is 1970 and 1971.
1972 Speedway torque converter.
Below are some details to a 1972 Speedway Blue Angle. Notice the throttle and
grips and brake lever. The throttle and brake lever are 'cherry' style (made in
Japan) types. The grips are incredibly hard, and really not comfortable. That's
why you don't see originals too much!
1972 Speedway handlebars.
The engine used in 1972 for the 14" wheel bikes is a Tecumseh model HS40-55395c in black
(no lighting coil), as seen below.
1972 Speedway Tecumseh HS40 spec #55395c on a Blue Angle. On a Red Baron with
lights, the HS40 spec is generally #55389c.
In 1972 Speedway had a nice
that came with their bikes. It lists all
the 1972 models inside, it's very complete, and applies to 10", 14" and 16" wheel bikes.
1973 Speedway Mini Bikes.
The 1973 Speedway catalog
shows a trimming of their tranditional 10" and 14" wheel Tecumseh engine based models,
and expansion of their Sachs/Fugi 2 cycle motor models. It was a
move to bigger bikes. Frankly probably not a great move, as the Japanese bikes (Honda, etc.) were really
taking over that market of 2 cycle bikes.
mid to late 1973 Speedway tag style serial number.
The stamped serial numbers in 1973 were in the mid 30,000 to high 30,000 range.
Then in mid to late 1973, Speedway changed to a riveted tag for the serial number.
The 'tag' style numbers were in the 40,000 range, but early to mid 1973 serial
numbers were still stamped into the frame (and were in the mid to high 30,000 range.)
About the same time Speedway changed to all black frames. No more colored frames
like prior years. The only thing not chrome or black was the gas tank and lower fork stays!
Also in the summer of 1973 they switched to a Salsbury torque converter system.
When they switched to the Salisburys they also had the clutch cover cutout modified so it would fit.
And on 14" wheel bikes, the handlebars changed - they got lower and added a motocross
style cross brace. It really changed how the rider sat on those bikes, and it's not a
change I personally really liked.
Fork caps and boots for 10" wheel models changed in 1973.
The mounting of the gas tank changed in 1973. It's the same gas tank, but now it
has four mounting points (instead of three). It sort of mounts like a Rupp gas tank. The single
connection point under the front edge of the seat is gone (because gas tanks were breaking at this mount.)
Now four holes are drilled through the
top tube of the frame on the sides (like Rupp) to bolt the gas tank.
Also the neck bolt changed sizes from 5/8" (normal for pretty much any mini bike) to 3/8".
Obviously the nylon neck bearing changed to accomodate this. The rear fender mounts changed too,
because a cracked rear fender was very common on the 10" wheel models. The mounting holes
were enlarged, and rubber grommets put in the holes. This helped, but the rear fender still
would crack behind the rear mount. And finally the 10" tires changed. No longer where those
nifty motocross aggressive tread tires available - all 10" wheel bikes had smooth trials
style tires installed. Also Speedway changed the plastic front/rear wheel spacers on 10"
wheel bikes from plastic to metal.
Fork trees on 10" wheel bikes changed in 1973. Left is a 1971 front fork, right
is a mid 1973 front fork (notice the tree plates are no longer flat steel.) Also
notice the fork cap oil bolts are plastic on earlier models, and metal on
Some other construction things changed in 1973. The front forks changed on the
10" wheel models to be more consistent with the 14" wheel models. For example,
the front fork cups changed on the 10" wheel models to be identical to the 14"
fork cups. This changed the caps and the rubber boots. Also the construction of
the fork tree changed too. Instead of flat plates for the tree, they are now
1973 Speedway Scorpion, non-stock carb.
The top line Speedway was the Super Spyder with a 125cc Sach motor and 5 speed transmisiion.
This bike had a 17" front wheel and 16" rear wheel. This is no mini bike! The Speedway Enduro
model was next up with a 100cc Fugi motor and 5 speed transmision. The Enduro had a 16" front
wheel and a 14" rear wheel. This bike had lights too.
A similar bike to the Enduro was the Speedway Motocross, which was basically a
light-less Enduro (all features the same as the Enduro, minus lights).
The Widow Maker had a Sach 80cc motor with a torque converter and 14" wheels.
April 1974: the End of Speedway.
The Tecumseh engine powered bike models were scaled way back. The Green Horn and Blue Angel
are gone. Now the only 14" wheel model with a Tecumseh 4hp motor is the Red Baron (introduced in 1972).
Uses a Comet torque converter (until late 1973) and still has full lights.
The only 10" wheel models are the
Scorpion (lights) and the Shrike (no rear suspension and no lights). That's it for the entire
Speedway 10" wheel line in 1973 (Scarab and Shark are discontinued).
The Scorpion and Shrike both use a Tecumseh HS40 four horsepower engine.
These do look quite a bit different with the black frame and flat tail.
In 1973 Speedway's future was looking dismal. The Japanese invasion of good quality
mini cycles at low prices was just killing Speedway (and many other mini bike makers.)
The competition from Japanese bikes was just too great to over come.
Then in April 1974 Speedway Products was sold for an undisclosed amount to Fox Corporation (Janesville, WI)
according to Bill Graff, a Fox spokesman.
The company acquired "the entire Speedway line and most of the company's assets".
John Morrow, former Speedway president, also moved to the Fox Corporation and was
named Vice President of operations. Unfortunately that was the end of Speedway.
It was a good solid run of good quality mini bike (and mini cycles.)
1974: Speedway's Last Bike Model?
In 1974 a Speedway bike appeared in the JC Penney catalog.
It was basically a 1972 Speedway Green Horn (the bike was even green, though a different shade),
but labeled as "El Tigre." It used a Salsbury torque converter (opposed to a
Fairbanks Morse/Comet set up.) The paperwork (owners manual) for the El Tigre
was dated March 1974. Now did Speedway sell JC Penney this bike, or was
this Fox Corporation using leftover Speedway parts? It appears the deal was set up
with Speedway, but Fox probably did the production of the bikes.
Fox sold Speedways are pretty rare. You can tell them because the lettering on
the gas tank is different.
1974 Speedway/JC Penney El Tigre mini cycle. Basically the 1972 Speedway Green Horn
re-labeled and sold by JC Penney.
Speedway Repair Info.
Speedway did some non-standard things that will come up if you
are repairing or restoring one of their mini bikes.
Typical Speedway 10" wheel mini bike head plate frame crack (blue circle).
It's not hard to fix, but something to keep an eye out for.
When buying a 10" wheel Speedway, always check the head plate for cracks. This is
a really common problem, as seen in the picture below. I believe this happens
because the front fork springs are too soft (or the front end has seized.)
With the front forks bottomed out, the energy has no where to go, and the frame cracks at the
The motor plate always seems to be swiss cheese on Speedway mini bikes
(especially the 10" wheel models). I think this happens because of the
problems with their original torque converter system, and lack of part
availability. Hence people hack in other clutch systems that require
the motor to be moved (or slid to adjust a chain.) This is frustrating to me, because I don't
like swiss cheese engine plates! I generally TIG weld the extra slots
and holes shut, and re-drill the four motor plate holes (2 5/8" from
the top edge of the motor plate to the center of the forward most two 5/16" holes)
Typical Speedway 10" wheel mini bike motor plate (Scarab). There should be
four holes (not slotted!) Obviously someone changed their mind about
motor positions (probably to accomodate different clutches.)
Using a TIG welder to fill-weld the old holes and re-constructed
the correct motor position holes (2 5/8" from front edge of motor
plate to the center of the forward most two holes). When the frame is painted this will
look pretty good (compared to swiss cheese!)
The 10" wheel bearings and axles are interesting. For some reason Speedway used
3/8" or 1/2" diameter axles (when the stardard was 5/8"). This is just weird
to have that small of an axle. Luckily the wheel bearings are the
standard 1 3/8" OD and 5/8" ID bearings, but they used a spacer that goes
inside the hub and into the bearing for the 3/8" axle. The spacer is 3/4" diameter with
a 3/8" hole drilled down the center (for the axle.) And the ends of
the spacer are machined from 3/4" to 5/8", to fix inside the 5/8"
The front and rear 10" wheel bearing spacer used by Speedway. Total length
is 3 7/8", with the center 3/4" diameter section being 3" long. The ends are
cut to 5/8" diameter to fit inside the wheel bearings. A 3/8" hole runs down
the center for the wheel axle.
In 1973 though the axles changed on 10" wheel bikes - they now had 1/2" diameter
axles front and rear. Instead of using the special center wheel bearing spacer that fits inside
standard 1 3/8" x 5/8" bearings, they changed to 1 3/8" x 1/2" bearings. This is a
major drag because 1 3/8" by 1/2" high speed wheel bearing today are impossible to find.
That means you have to re-use the original bearings, or convert to a 5/8" axle and
use standard 1 3/8" x 5/8" bearings.
Because the 10" wheel bearing spacer is non-standard, if it's missing, you have to come
up with some sort of a solution. If you're only missing one, what I do is
convert the rear wheel to a 5/8" axle. You will have to drill the swingarm
(or frame on a Shrike) from 3/8" (or 1/2") to 5/8" holes. Also the brake plate will
need to be drilled too. Then any sort of bearing wheel spacer (nothing special) with
a 3" length (goes inside the wheel hub between the two new wheel bearings)
can be used along with the much stronger 5/8" axle. Also the sprocket
side axle spacer will need to have a 5/8" hole too. I don't do
this on front wheels because the drilling is more involved, and the welded hole
on the front tubes are set up for a small nut (a larger axle nut won't fit
inside the tube.) It is possible to use a 5/8" front axle, but it's more work
and perhaps not worth it. But on the rear wheel it's very easy to use a 5/8" x 7" axle
(if you have a 5/8" drill bit and some 5/8" ID hole spacer/pipe material.)
Converting a rear 10" wheel to a 5/8" axle. It's not that hard, but you
will need a 5/8" drill bit. The brake hub hole and aluminum hub stop (blue arrows)
will need to be drilled out to 5/8". Also a new 1" hub spacer will be needed (5/8" hole
for the sprocket hub side, red arrow).
And of course a 5/8" axle (7") and nut with new 5/8 ID wheel bearings.
Obviously the swingarm axle holes will need to be drilled out to 5/8" too.
On 14" wheel bikes they also used a smaller axle too. I have converted
these to 5/8" axles too, but for a different reason. The wheel bearings on the
14" wheel bikes are metric with a metric sized axle, and it's hard to find replacements bearings that have
the original ID hole for the metric axle. Hence using a standard 1 3/8" OD by 5/8" ID bearing and new 5/8" axle
is a good solution (if you need new wheel bearings.)
The front and rear 10" wheel plastic sprocket spacers used by Speedway.
Left most is for the rear wheel, center/right is for the front wheel
disc brake plate. Right spacer is the later metal style.
Another issue on Speedways is the plastic wheel spacers for the sprocket or
front disc plate. For some odd reason Speedway used plastic spacers for this.
That may be fine 40 years ago, but today they are often cracked/compromised.
In 1973 Speedway figured out this was an issue and started making them
out of metal. But for the first couple years they were plastic. The only
solution is to make a new one out of aluminum or buy new ones (I see them
on ebay for $100 a pair.) No easy task to make them unfortunately.
And the problem with plastic wheel spacers becomes bigger with larger/more powerful engines often used today.
A damaged 10" rear wheel sprocket spacer. This is the problem with
a plastic spacer...
Original Speedway driven 5" torque converter and jackshaft. The compression spring
for the unit is under the black plastic sleeve. It's an odd design, and you'll never
find parts or a belt for it. Also hard to work on as the pieces are pinned to the jackshaft.
This is why I use a new standard style jackshaft and Comet 6" driven symmetrical series 20
to replace the entire unit. Bike will perform much better too with the new set up.
The gearing for Speedway mini bikes is important. If you gear too high,
there's not enough power. If you gear too low, not enough top end speed.
Personally I find 30 to 40 mph to be the top speed to hit with a
stock Tecumseh HS40 or HS50 engine (at 3600 rpm). With that in mind, this is what
the bikes used originally for gearing (which seems to work well) via
the 7.5" jackshaft 5/8" diameter with a Comet series20 torque converter.
The calculations below assume a 16.5" tire height for 10" wheel bikes,
and a 20.5" wheel height for 14" wheel bikes:
- 10" wheel bikes: 54 tooth rear sprocket, 11 tooth jackshaft, 4.9 to 1, yeilding about 37mph.
I consider this the ideal set up.
- 10" wheel bikes: 68 tooth rear sprocket, 9 tooth jackshaft, 7.5 to 1,
yeilding about 24mph. I change this to a 14 tooth jackshaft sprocket giving 4.9 to 1.
- 10" wheel bikes: 48 tooth rear sprocket, 8 tooth jackshaft, 6 to 1, yeilding about 30mph.
I change this to a 10 tooth jackshaft giving 4.8 to 1.
- 14" wheel bikes: 54 tooth rear sprocket, 10 tooth jackshaft, 5.4 to 1, yeilding about 40mph.
I do have one 14" wheel bike (my Red Baron) with a 9 tooth at the jackshaft (6 to 1) yeilding 36mph
(this allows the motor to rev higher for more power but lower top speed.)
On 10" wheel bikes personally I find the 4.9 to 1 ratio to be the best with a Tecumseh HS50 engine.
If you are using a smaller engine (HS40 or H35) then other ratios may be better. On the 14" wheel
bikes the drive ratio needs to be different (5.4 to 1) because the rear wheel is bigger.
Personally I always make a new jackshaft. I buy lengths of 5/8" rod with the 3/16" keyway
milled into it, and cut it to 7.5" length. Usually end up taking .050" to .075" off that
length for a final fit. Use new 5/8" jackshaft bearings. Drill the ends of the new jackshaft
about 3/4" deep with an "H" bit (.266"), and then tap it with a 5/16-24 drill bit about 1/2" deep.
This leaves the end of the jackshaft flush with the outside of the jackshaft bearings. Using
two 5/18-24 bolts 1/2" in length and a washer works great. Some
people like to use 5/8-18 nylon locknuts on the end of the jackshaft (you will need a longer jackshaft
and a 5/18-18 die to do that.) Personally I don't go that route, but if you prefer, that works too.
I also make jackshaft spacers from 3/4" stainless steel tubing (with a .035" wall thickness.)
Do *not* use or trust anything with an allen wrench screw! You will regret that, trust me.
Using spacers means no allen screws on the jackshaft sprocket. That's the right way to
do this. Allen screws always find a way to loosen, and at the most inappropriate times...
The torque converter (TC) used on most 10" wheel bikes for the first three years was
a 5" driven 5/8" wide belt custom style symmetrical unit made by Speedway. Yet another problem as belts and
parts for this are impossible to find. Later 10" wheel Speedways went to a 6" Fairbank Morse driven
torque converter, but again, parts are hard to find (and the entire jackshaft/TC setup is hard
to work on.)
Because of this I convert to a
standard 6" driven Comet symmetrical torque convert (series 20)
and a Comet #203578 (3/4" wide) belt. You will get much better performance
and parts are easy to get. You will need a new 7.5" long 3/16" key slotted 5/8" jackshaft
(with end bolts). But that's pretty easy to construct.
Make sure you use spacers on the jackshaft (don't rely on set screws/colars!!)
I drill both ends of the 5/8" jackshaft and tap for 5/16-24 bolts. Install new 1 3/8" by 5/8"
bearings (they fit right into place.)
Believe me, it's worth it to do this conversion on the 10" wheel bikes.
For the 14" wheel bikes, they should have an updated torque converter (maybe
even a Comet) with a 6" driven unit. They will use a 5/8" wide symmetric belt, most likely the
Comet #200419 belt. These bikes can be updated to the newer style Comet
series20 with a 3/4" belt too (using a Comet #203578 belt), but the benefits
are less obvious than the conversion on a 10" wheel bike.
The big problem with 10" wheel Speedways with 5" driven 5/8" wide belt is the original torque converter belt.
Unfortunately I do not have a replacement number for you! You can not use a Rupp
(Gates 6061) belt, it's too big (see picture.) This is probably the main problem,
and why I convert to a Comet series20 (with a readily available 3/4" wide #203578 belt.)
Here's a comparison of an original Speedway belt and the Rupp/Gates 6061 belt.
As you can see, they are a different length, and not interchangeable.
To do this conversion the frame opening for the driven needs to be enlarged slightly. Note the pictures
below which show this. Also on rear suspension 10" wheel bikes, I move
the swingarm back about 1/2". Though not completely necessary, it gives more room between
the belt and the front edge of the swing arm. This involves a bit of welding
(to extend the frame pivot point), so it's probably not for most people. Note you
don't have to do this on models without rear suspension (like the Shark or Shrike.)
Enlarged driven torque converter hole on the engine plate for a Scarab. A comet 6"
series 20 driven is fitted here with a 203578 belt.
Red arrows show the portion of the engine plate that was slightly enlarged
to accomodate the 6" series 20 Comet style torque converter.
Here the Comet series20 installed on a Speedway Scarab.
Here the potential problem on 10" wheel suspended Speedway mini bikes...
the front side of the swing arm can touch the new 6" driven Comet.
For this reason I move the swing arm pivot points back 1/2" so
there's no interferance.
Here the problem can really be seen in the picture below, where
the new 6" torque converter driven interferes with the position
of the swing arm.
Here's the stock swing arm pivot point that we will be modifying
on this 1971 Speedway Scarab.
In order the extend the swing arm pivot point, it is a bit of work.
Here's how I do it so the Comet 6" driven won't hit the front edge
of the swing arm. Note depending on your chain, this may not be
necessary. It just depends... If the swing arm is adjusted back
all the way and your chain tension is good, you may not have to do
this. As a rule I always do it, because I just don't want any issues
(and I have a TIG welder.)
Here's some added metal welded to the swing arm tab on the main frame. Also the front 1/2"
edge of the slotted hole was fill welded. That's because the whole pivot section is
moving back about a 1/2 inch.
Here's the added metal ground flat to blend with the original metal.
Now the swing arm adjustment slot is re-cut. Also a metal tab (which is an upside down
allen head screw with the screw part cut off) welded in place. This is the point where the adjustment
wing hits to make chain adjustments easier.
A swingarm from a 10" wheel bike and the metal 5/8" by 7" long pivot rod that goes inside.
Note both the 10" and 14" wheel bikes use the same 5/8" by 7" long pivot rod. ALWAYS re-grease
this pivot rod so it won't seize inside the swingarm pivot tube.
The swingarm is another factor that should be checked. There is a 5/8" metal pivot rod
drilled/tapped with 3/8-24 threads on both sides. This rod should
spin inside the swing arm tube! Usually it's rusted in place, and will need to pressed out.
It the rod does not press out easily, STOP. It is easy to distort the swingarm if you
use too much pressure. Instead drill out the frozen rod! The rod is rather soft
leaded steel and will drill easily. They used leaded steel because it's easier to drill and tap.
To drill out the rod, start with a 3/8" drill bit and finish with a 5/8" drill bit. I use a mill for this task.
If you can press out the rod, cleaned up the outside, re-grease it, and re-use (always grease the
pivot rod.) But usually
I have to make a new 5/8" rod (7" long) and re-tap the ends 3/8-24 and 3/4" deep. IT IS VERY IMPORTANT that
this rod moves inside the swingarm tube! If it doesn't, the bolts at the ends will constantly
loosen, and the chain will throw. Note all Speedways with rear suspension use this 7" long 5/8" diameter
swingarm pivot rod (both 10" and 14" wheel bikes.)
Speedway 14" wheel fork disassembled.
The front forks on Speedways can also be a challenge. Note they do use oil,
specifically two ounces of 10w hydraulic oil per side. So the top seal needs
to be intact or they will 'bleed'. Both the 10" and 14" wheel forks use oil,
and are basically constructed the same.
Often the parts are just worn out. For example, the seals and the brass ring
takes a lot of abuse (especially on the heavier 14" wheel bikes.) I haven't
noticed the brass rings to be bad on 10" wheel bikes. But on 14" wheel mini bikes,
the always seem to be wasted. To rebuild them you'll need some parts (note these
are for the 14" wheel front forks, the 10" wheel fork may require different
seals and brass rings):
The original Speedway nylon fork strut bushing from a 14" fork, which is junk.
- Bronze bushing 1" ID 1.25" OD 2.5" length. Mcmastercar #6391k45
- Buna-N Rubber U-Cup Seal for 0.282" Groove Width, 0.955" ID x 1.545" OD x 0.25" Wide. McMastercar #9691k57
- Old and used Rupp 1971-1975 Front fork strut bushings #17496. The more used, the better. (You can also
buy these brand new from Blackwidow Motorsports.)
First need to get the old Speedway forks apart. Mine were tough birds.
The original nylon bushing inside was jammed (and destroyed), and made taking the forks apart
difficult. In theory unscrew the fork cap (aka packing nut) and slide the fork apart. Then there's a large
threaded bushing at the end that allows the parts to come off the upper strut.
There should also be a spring in the lower strut.
Have to deal with the nylon fork strut bushings. I do not know a source for original Speedway versions,
but we can take some old (used) Rupp 1971-1975 strut bushings and modify them to work
(#17496 Rupp fork strut bushing 1971-1975.)
On this 14" speedway wheel fork, the Rupp version needs to be cut to 5.75" in length.
For 10" wheel bikes, the length is 2.5" (assuming a bronze bushing, early models) or 3 1/8" (no brass ring,
later models.) I used a band saw to cut the nylon tubes to size. On 10" wheel bikes you use the
bottom smooth section. On 14" wheel bikes you need the top "lip" portion.
Used Rupp front end bushings, will cut to the proper length for use on a 14" wheel fork.
After you have them cut to length, the ends need to be modified.
The rupp version has too big of a lip on the edge. That needs to be sanded to fit
inside the Speedway fork screw-on cups. I used a belt sander to do this. Also the
second (lower) lip needs to be removed. Again I used a belt sander to do this.
Note on 10" wheel bikes the lip arrangement is not used at all. Just cut the
old rupp bushings to 3" (or 2.5" on early models with the brass ring) and you're done.
After the used Rupp fork struts are sanded, the end should fit easily inside the Speedway fork screw-on caps.
Used Rupp front end bushings, cut and modified for the Speedway 14" wheel fork.
Now comes the tricky part. On the 14" wheel Speedway screw-on caps (packing nuts), there's a bronze bushing inside.
On my forks, this bushing was so worn, it was like a hotdog in a 55 gallon drum.
The wear was also uneven. Check out the picture below. They should be 1" inside diameter,
and 1.25" outside diameter. And .200" tall.
Also the rubber seal inside the screw-on cap was worn to death too.
That will need to be replaced too.
On the Speedway 14" wheel fork, dealing with the worn bronze ring.
Again these parts probably aren't available anywhere. But Mcmaster Car has some material
that works. I bought their bronze bushing 1" ID and 1.25" OD and 2.5" long. I put this
on a lathe and cut it like a pepperoni to a thickness of approximately .200". I don't think this
thickness is really that critical. If you don't have a lathe, you can cut them with a hacksaw
(and then sand it clean on a belt sander.)
McMaster Car also sold some decent rubber seals. Not perfect replacements, but pretty good. It
will work. And they are cheap, like (5) of them for about $5.
On the Speedway 14" wheel fork, old versus new parts.
Original brass ring on left, new ones cut and ready for use.
10" wheel forks on a Speedway Scarab. Note the nylon liner is much smaller than
the 14" wheel bikes. Some have that 1/2" brass ring at the bottom, some do not. The length of
the nylon sleeve will vary from 2.5" to 3 1/8" depending on the existence of that 1/2" brass ring.
The front fork springs are another issue on both the 10" and 14"
wheel bikes. They were probably too soft from the start, but time never
does well for compression style springs. The original compression springs for
the 10" wheel front forks were 6" long, 1" OD, .775" ID, wire diameter .100" thick.
I've opened a good number of Speedway forks and found these front forks
to be compromised and/or broken. I'm looking for a good suitable replacement.
I have found a spring from Zoro.com which is
Raymond blue spring #103524
and have tried them in a 10" Speedway front fork. This spring is rated at 80 pounds per inch
and is 6" in length and 1" in outside diameter.
They are the right size, but way too firm.
To counteract this, I found cutting off 1/2" to 3/4" from the Zoro spring helps, as this gets
rid of the forks springs' pre-load. But it's still too stiff. A better spring is the
Raymond green spring #302524,
it seems to be about perfect (at 50 pounds per inch, 25mm x 152mm). The disadvantage to this spring is
you need to order in packs of five, and they usually take about a month to show up. Again with this
spring I cut off 1/2" to 3/4" from the length so there's no pre-load in the fork. I am quite satisfied
with this spring, it's just about right in firmness for me.
THere is another possible spring,
Raymond spring #302532d
which is 38 pounds per inch, but is 8" long.
Obviously you can cut this to 6", so it may be a good solution too (though I have not tried it.)
Bottom spring is the original Speedway 10" wheel front fork spring. The green Raymond #302524 spring is
the ideal spring, with 1/2" cut from the length (so there's no pre-load.) The blue Raymond spring #103524 (top) is really stiff, even
with 1/2" cut off the length.
On 10" front forks, Speedway changed their mind on how the bottom of the non-moving
portion is locked in place. At one point the brass keeps was threaded into the
non-moving fork portion. But at some point they changed to a 1" snap ring, and the
brass keeper is just pressed into the bottom. On this variety most often the
1" snap ring is usually junk. You can replace this with a hardware store 1" external
snap ring. Just put this on the end of the fork, and then use a sander to take off
the exterior so it's 1.125" in exterior diamater (yes you will grind off the
snap ring holes.)
Hardware store external 1" snap rings can be used
on the 10" Speedway front fork bottoms.
Also make sure you use a 1/16" drill bit and clean out the 10" front fork brass end keeper.
If this hole is blocked, the oil in the front fork can't move through the tube
and the front fork!
The 10" front fork with a new nylon Rupp front strut, new 1" snap ring, and the
press-in style brass end. A 1/16" drill bit is used to clean out the hole in
the end of the press-in brass keeper.
Speeedway fork repair document.
Also on the top of the 10" wheel triple tree bikes before 1973 they
used red plastic bolts. If you removed these, you could add oil to
the forks. Unfortunately since prior to 1973 these were red plastic,
they are often broken or missing. You can replace them with short
10" Wheel Front Disc Brake Repair (missing caliper.)
A good number of 10" wheel models had a front disc brake. Unfortunately
they are usually missing the caliper portion of the brake. For this
discussion we'll assume the disc brake rotor is installed on the front wheel
(though you can make a new rotor out of 1/8" thick steel, 6" diameter with a 1 7/8" center hole)...
But the big question is, how do you deal with the missing front disc brake
Speedway brake parts are impossible to find. So is there a way to adapt
a different and more common front disc caliper to the Speedway 10" wheel bike?
Turns out there is a way, but it involves making a small metal bracket
and utilizing a DB30 mini bike disc brake caliper.
The elusive 10" wheel Speedway front brake caliper assembly. This goes missing for a lot of reasons.
Mostly because other mini bikes of the period also use this assembly, so they are
stolen and transplanted.
Original 10" Speedway front wheel and disc brake rotor. No disc brake caliper though...
First step is to get some parts. You'll need some 1/8" thick steel,
a couple 1/4-28 bolts (1" long), and a couple 3/8" OD metal spacer.
That stuff is hardware store material. The actual DB30 disc brake
caliper can be bought on ebay for about $20.
Two metal spacers and two 1/4-28 bolts (1" long) are needed.
First up is to cut a part from the 1/8" flat steel with two 3/8" holes. It needs to look like the
picture below. Also need those two 1/4-28 bolts and two 3/8" metal spacers (seen above.)
Or if you like you can download the
front brake TIF file and print it on paper to cut the part.
Or better yet download the DXF files below and have them laser cut:
I use the website sendcutsend.com to upload the DXF files
and they cut the parts from those files. This is really convenient and quite inexpensive. The disc rotors
I have cut in stainless steel in .100" thickness. The other parts use .125" thickness.
Make your own metal bracket from 1/8" thick steel and drilled with two 3/8" holes so you can
mount a DB30 style disc brake to the Speedway front forks (or use the DXF file above and
have the part laser cut.)
Original front Speedway disc brake rotor (left) and new stainless steel
version made from the above DXF file (right.)
What we will do is weld this metal bracket to the lower front fork tube.
The new DB30 brake caliper will float on the bracket. This is important... the
caliper must float through the two 3/8" bracket holes and the metal spacers.
I tap the DB30 caliper for the 1/4-28 (it's originally a slightly smaller metric size.)
Here's the DB30 brake caliper floating on the bracket.
Here's the brake caliper bracket welded to the front fork, and the DB30 caliper installed.
So how well does this front brake work? Well pretty darn well!
Though I should mention one more thing... the DB30 caliper is set up for a .100" thick brake rotor.
The original 6" brake rotor on the Speedway front wheel is 1/8" (.125") thick. I used two washers
on the brake caliper to space the stationary disc brake pad out, to accept the additional
thickness of the Speedway brake rotor. This involved removing two allen head bolts and installing
a washer between the stationary pad holder and the caliper for each bolt (super easy.)