Thinking of going with the 212cc HF engine over the 3.5hp one on the bike now, does anyone have picks of one installed ? what TC do i need, belt, etc.. the little 3.5hp on her right now runs good but its side exhaust and looks like it has a mis matched clutch on it so maybe better to start from scratch. sorry for all the questions but its been 30 years since i last had a mini bike!!
Rupp roadster with preditor
- Thread starter 71demon340
- Start date
a predator on a rupp frame makes for a little rocket.
I had one on my black widow for a short time. Used a comet 20, Rupp driven, and the belt I already had, not sure what lenght. Just measure center of crank bolt, to center of driven jackshaft, and look at the chart on bmi's website.
It was a wheelie monster..
I had one on my black widow for a short time. Used a comet 20, Rupp driven, and the belt I already had, not sure what lenght. Just measure center of crank bolt, to center of driven jackshaft, and look at the chart on bmi's website.
It was a wheelie monster..
30 series won't work.the 30 driven has to be mounted with the spring outwards and will not work on the rupp.more pics in here http://www.oldminibikes.com/forum/project-logs/58729-70-rupp-project.html
also did a 71 the same way http://www.oldminibikes.com/forum/project-logs/58730-71-hustler-project.html
also did a 71 the same way http://www.oldminibikes.com/forum/project-logs/58730-71-hustler-project.html
All you need is a custom exhaust kit and a new 5/16-25 bolt for the TC mount. The output shaft is shorter but not an issue regarding function. You can even run the stock exhaust if you don't mind a little heat by your leg (it's quiet!). I used the stock air cleaner with a little trimming. It fits the stock frame mounting holes perfectly and doesn't have any significant clearance issues.
The one I got had a minibike type throttle attachment, just added a return spring.
You can use the stock clutch, but it will pull just a little bit at idle because of the higher RPM of the idling predator and will be quite "soft".
After doing the swap I then upgraded to a Comet 20 sold by rupparts.com (for use with a 5/8" stock belt). It launches much harder and pulls better but is more difficult to ride because of that. What I had on my rupp originally was a 1/2 drive-driver, the comet 20 drives both sides so it pulls harder.
That predator has so much power you'll be looking for taller gearing too, you max it out very quickly with almost double the hp and torque and want some more. I kept mine governed.
never tried the full upgrade 3/4" belt with comet 20 driven, not sure how the comet 20 driven would mount to the rupp frame (it might work with no issues, no idea).
WARNING::: This makes this bike a grownup only machine.
The one I got had a minibike type throttle attachment, just added a return spring.
You can use the stock clutch, but it will pull just a little bit at idle because of the higher RPM of the idling predator and will be quite "soft".
After doing the swap I then upgraded to a Comet 20 sold by rupparts.com (for use with a 5/8" stock belt). It launches much harder and pulls better but is more difficult to ride because of that. What I had on my rupp originally was a 1/2 drive-driver, the comet 20 drives both sides so it pulls harder.
That predator has so much power you'll be looking for taller gearing too, you max it out very quickly with almost double the hp and torque and want some more. I kept mine governed.
never tried the full upgrade 3/4" belt with comet 20 driven, not sure how the comet 20 driven would mount to the rupp frame (it might work with no issues, no idea).
WARNING::: This makes this bike a grownup only machine.
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a preditors never gona look right in that frame. why not just put a bigger flathead. iv herd the tecumseh hs50 is a good upgrade for that bike and looks fairly correct for the frame. if that isn't powerfull enough for you the tecumseh h50 h60 and h70 also fit and have even more power and torque. they dont look quite as good in the frame as an hs50 but still look better than a preditor.