I buy and collect Fox minibikes. 9/1/18. Email: firstname.lastname@example.org
Overall Fox History and Info.
Fox Corporation started just after WWII in 1946, selling motorized vehicles. Mostly stuff like farm carts and golf carts and later snowmobiles. But in 1958 Fox got into the go-kart market selling their "Go Kart" brand of fun carts. This fad seemed to fade a bit and by 1965 Fox was making minibikes too. Their first bike seemed to be the 1965 Fox Little Gen and it's 2.5 or 3hp motor (probably Lauson.)
In 1966 Fox started to get more serious about minibikes and introduced their "Sport Bike" (2.5hp Lauson) and "300" models (3 or 4hp Briggs) mini bikes. The 300 model had 6v lights, full suspension, jackshaft, fancy fenders and gas tank covers, centrifugal clutch. This can be seen in their Fox catalog #6, along with their go karts.
A first for Fox (and something many others followed) was the 20 degree slant motor mounts and a jackshaft (but no jackshaft on the Doodle bug, but it too had the slant motor mount). This 20 degree motor mount was known as the "tilt power plant" and was a first on the Fox 1969 models. Tecumseh was the motor of choice too, as Briggs was trying to get away from mini bikes. To get around the float bowl issue on the carb/slant motor issue, they used a diaphram carb. Single speed bikes used centrifugal clutches and dual speed minibikes used a 2-speed automatic clutch system, which utilized two centrifugal clutches (one on the motor and the other on the jackshaft.) This set up used a centrifugal clutch with two chains going to the jackshaft.
In 1971 Fox again changed their mini bike models, probably again to follow Rupp's changes. A Fairbank Morse torque converter was the norm for most models (the 2-speed automatic centrifugal clutch set ups were gone). This dramatically increased the power of the bikes, as the Fairbank Morse converters were a very good design. Suspensions were bulked up too, again probably to compete more with Rupp. The Tecumseh diaphram carb was no longer used (a change Rupp made too). Instead a slant intake manifold was utilized to keep the float bowl carb level (because the 20 degree motor mount.)
In 1973 the Fox/Dynamark line had mostly spooked wheels mini cylcle type bikes (Thunderbolts.) This is seen in their Fox minibike catalog 1973. In addition to the Thunderbolts, they also offered a Tecumseh mini cycle with lights and a speedometer (Thunderbolt 200mc). The Thunderbolt 125 used a 3.5hp Tecumseh and only had front suspension and a clutch. The Thunderbolt 150 had front and rear suspension, a 4hp Tecumseh motor, and torque converter. In 1973 the Thunderbolt 198mc was introduced with a really cool leading link front suspension, 5hp Tecumseh, and torque converter. The Tunderbolt 200mc was top of the line and really a full motorcyle with a Tecumseh 2 stroke motor (though no gears, used a torque converter.)
As an interesting side note, Fox Corp bought out Speedway in the spring of 1974.
Speedway rose from 1970 to 1973, and then died (Speedway was a Division of Taylor metal products.)
I'm not sure what benefit Fox got from this purchase, as their models are different than the big wheel
Speedway mini bikes. Here's the news bulletin on this:
The 1969 and 1971 and 1973-1975 Fox mini bike catalog(s) have largely escaped me (does anyone have a copy they call sell me or at least let me borrow to scan???)
Below are some pictures of these bikes I personally own, restored, or have seen. Fox was definitely moving to more mini-cycles than mini-bikes with many of their models, increasing the wheel size to as large as 14" diameter. Again this followed what Rupp and Speedway were doing at the time. Their Thunderbolt and Desert minibike/minicycle models were the new flagships of the mini bike model lines. Note most models had "TC" and "4HP" round stickers on the original torque converter covers, signifying their proudness for the 4hp Tecumseh motors and Fairbank Morse torque converter. But by 1975 Fox had moved to Comet brand torque converts (probably price dictated that move.)