GEBE belt tensioner jumping....possible cure?

Discussion in 'Rack Mounted Engines' started by motorbikemike45, Jul 12, 2010.

  1. Belt jump was a problem on my GEBE-Robin bike from day one, especially under hard(?) acceleration or when climbing hills. I cured it once with HDPE poly washers I cut from a milk container and lubed with grease on both sides of the tensioner. Over time the problem resurfaced. I cleaned the dirty grease from all surfaces and lubed them with a dry molykote lube, but got some jump. Replacing the washers with new ones lubed with moly worked for a time, but the jump resurfaced after a while.

    I pondered long and hard over this and last night as I was drifting off to sleep a possible solution came to mind. The tensioner pivots on a 1/4 inch Allen head cap screw, ON THE THREADS. Today I bought a new bolt where the threads stop about 1/4 inch from the bolt head and installed it from the opposite side, so the tensioner rides on the non threaded section of bolt. I also used brass washers on both sides of the tensioner and lubed everthing with molykote.

    I just got back from a test ride and there is absolutely no belt jump at all. Time will tell if I've finally hit on a good and permanent solution. The tensioner attempting to pivot on threads instead of a smooth, round shaft is poor engineering. Now that it is pivoting on the round unthreaded shaft of the bolt it feels as smooth as glass. Of course I will need to fine tune this mod as the tensioner will not stay in the up, loose position as the spring hits the back side of the long bolt and the nylon inserted lock nut now. I need to cut the 1/4 X 1 1/2 inch bolt short and use a thinner standard 1/4 inch non-locking nut with locktight to clear the spring. I'll keep you GEBE users appraised here as time passes and my idea either works as I think it should, or if the jump recurs. Fingers crossed.

    If my idea works, I'll pass it along to Augie and GEBE.
     

  2. I hacked off the excess bolt and used a standard nut. Now the tensioner works as it should and I can loosen the belt as designed. Still butter smooth with no belt jump.
     
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