Thread: Rupp Chinese Clone Auto Shifting Difficulty

I have a Rupp Scrambler Trail 70 Chinese CT70 clone tha I purchased new in 2002 and put away and never used it. I ran gas stabilizer throught it and then ran it dry with the fuel shut off, so when I changed the oil recently and gassed it up it started up right away and runs just fine. I replaced the stock Chinese spark plug with a NGK and I am thinking about replacing the stock carburetor with a Keihin replacement even though it seems ok.

The only problem with the bike is that the 4 speed auto transmission has a difficult time shifting, especially downshifts. Upshifts can sometimes be difficult and it seems you have to hit a mid-high rpm level to get it to shift smoothly, but downshifts are usually only possible when the bike is virtually at a dead stop, no matter what gear you are in. I just tried the auto clutch adjustment by loosening the locknut on the left side of the crankcase, turning the adjustment screw all the way in gently until it just stops and then loosening it 1/8 turn counterclockwise, but it is still difficult to shift and now the bike surges each time you shift. I only did that for one block as I do not want to damage anything. But I am at a loss as to what to do next to correct the problem.

Also, the chain seems top be rubbing the chainguard bracket screw or frame tab and it makes a rubbing noise on and off.

Any thought as to the shifting problem, chain noise and do you think I should replace the chinese KV carb for a Keihin and if so ,which one? Any other recommentded parts upgrades. The bike is candy ruy red and seems well put together after comparing it with the local dealer's current Chinese Lifan CT70 clone offerings, even thought it was made in Chongqing Lifan back in 2002. I have just 40 miles on it from driving around the neighborhood recently and the bike is in perfect condition, so I would really like to get it up to spec and running perfectly. Thanks for your help.

George

The Rupp moniker was resurrected circa 2001 but didn't last very long. These bikes were among the better repops, at least in terms of finish detail. Jinchengs were the best of the lot; Jincheng is Suzuki of China. Your bike may even contain some jc parts as these were in wide circulation at that time and both pre-date the ebay race-to-the-bottom feeding frenzy. That bodes well in some aspects. Unfortunately, your engine may not be one of them.

The only things that will affect shifting are clutch adjustment and mileage. Lame shift quality has been common with Chinese trannies. That said, I still wouldn't expect it to as badly as yours. Usually, finding neutral or getting false neutrals are the main problems along with balky shifting...but gear changes are still possible with less drama than you've described.

Try adjusting the clutch preload trial-and-error style, retesting until you see improved shifting or clutch slip sets in. 1/8-1/4 turn incremements should be workable and it shouldn't take many of them before you either correct the problem or reach the point of slippage. 1000 miles of riding usually improves shifting as the shift forks/pins and drum wear-in. Another point worth mentioning is the fact that clutch preload can change as the engine heats up. Commonly, preload decreases after extended running time. That can result in incomplete clutch release and the shifting problems you have. Sounds to me like you've been making virtually clutchless gear changes.

Thanks, I'll give your suggestion a try and post the results. By the way, the engine is a Lifan engine, code1P47MFD. It seems fine if I could just get the shifting problem worked out.