I would guess that you have alighment issues. the width of the chain shouldn't matter if your sproocket and motor sprocket are alighned. Some of the kits come stock with a 415 which is even wider, this is what I use. I think I have one more 415 left then I will switch to the 41...Kelly

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I'm racin' Spitfire, turnin', poppin' wheelies, burnin' evil chasin' pop,pop, pop,pop,pop.... (The Pixies-Tony's theme)