Our latest bike build

Discussion in 'Mini Racing' started by earacing, May 30, 2012.

  1. earacing

    earacing Race Dad

    In between WERA West races and track days, we race on kart tracks to stay sharp. This is our newest build. It's an RS125 with a CR85 motor in place of the 125. It's the perfect complement to our 125s and we love it. :up:

    Racing this weekend at Adams with www.minimotousa.com !

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  2. backcountryme

    backcountryme Word to your mother.

    Sweet bike. A guy in our club has a tz125 with a crf150 in it. That thing is a rocket on the kart track
     
  3. cyclox

    cyclox moving chicane specialist

    nice! I'm thinking of building something similar. How difficult was it to get the engine mounted?
     
  4. earacing

    earacing Race Dad

    I bought the kit from Leonard Millgren for around $2,400 installed. I provided a full rs125 chassis minus the motor and he provided a CR85 motor, carb, and pipe. The cases are modified to fit into the stock mounts, and he did all the work. Not cheap, but a complete bike sells for around $5,000, so the kit price is good.
     
  5. earacing

    earacing Race Dad

    We had a couple of those. Sold one to buy a 125 a while back, and just sold the second one to pay for this build. 72 mph on a kart track is flying :)

    We made the switch because the 85cc 2-stroke is just as fast, and is a better complement to the 125.
     
  6. turbulence

    turbulence Well-Known Member

    nice bike!

    got any pics sans fairings?
     
  7. earacing

    earacing Race Dad

  8. Tdub

    Tdub Say what???

    Looks like engine and/or swingarm has been modified for better engine location. I like the idea of not modifying the downspars to make the engine fit and the engine located where it should be. Nice job! :up:
     
  9. 02R6

    02R6 The dude abides

    You're exactly right; it's the engine that's modified, not the frame. When I bought a KX65 engine from Leonard about a year and a half ago he told me about the CR85 engines he had for sale and said that the engines themselves had been modified, as Eric mentioned above. Here is what the modifications to the 65 look like:

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  10. earacing

    earacing Race Dad

    Thanks. That's correct, the cases have been modified, similar to the 65 above. We had originally cut off the front motor mounts and fabricated new ones to accept an XR100 motor built to 145cc. Same thing with both 150s that we had.

    Aaron Hamil is the guy that did all our chassis work. He removed the stock mounts very carefully before fabricating the new ones. For this project he removed the XR mounts and re-welded the stock mounts back onto the frame. I gave him a 125 motor so he could get it all lined up, and then pulled that out and gave the rolling chassis to Leonard. That will give me or a future owner the option of putting it back to a 125.
     
  11. backcountryme

    backcountryme Word to your mother.

    He welded on the frame? Wouldn't it have to be heat treated again? That engine is pure sexy. That is a ton of work, and looks like it was done nicely. I would love to have an RS or TZ frame. That is just not in the budget this year. I have one YSR and a pit bike that we are running right now and another YSR that I will be putting an XR200 engine in for next year. But some day there will be an RS or TZ in my future.
     
  12. blackbird2xx

    blackbird2xx Active Member

    I just picked up a 94 rs roller for my build. I am quite excited about it!!
     
  13. ACDNate

    ACDNate Well-Known Member

    Can you setup an RS chasis for an adult rider? I've seen some tail sections/subframes that were supposedly larger but haven't put my eyes on an RS setup for a larger rider.
     
  14. earacing

    earacing Race Dad

    I don't know, but we've had several bikes that were modified that way and never had a problem. Ran this one all last year and it held up great, even with that monster 145 in there.
     
  15. backcountryme

    backcountryme Word to your mother.

    Ahh, cool. I just assumed that the weld heat would anneal the aluminum. But if you haven't had any issues I guess I was wrong.
     
  16. blackbird2xx

    blackbird2xx Active Member

    What sprocket size did you use on the 145se rs? Was it a 420 or a 415, and where did you get them?
     
  17. Tdub

    Tdub Say what???

    Several years ago I built an RS105 hoping that WERA would allow the displacement in the 85 class...wrong :D The 105 was actually a destroked/underbore RS125 engine. 32HP on the dyno!! Shelved the project when there was no where to run it, but it was FAST!:D
     
  18. earacing

    earacing Race Dad

    We ran a 420 sprocket and chain. I had a bunch that came with our 150, and got a few more from Vortex.
     
  19. rob linders

    rob linders Well-Known Member

    Yes you can. They make tails that extend further back for the larger rider. They also make rearsets that go further back for the longer legged rider.
     
  20. raddad13

    raddad13 Well-Known Member

    what year rs are you using, Ive spoke to someone looking at the cr85 motor I have, and we were wanting to make sure it would fit the newer frame, I had it in a 94.
    my motor was also fabricated to fit so the frame wouldn't have to be.
    thanks
     

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