I'm guessing you mean that the actual drive chain (not the chain inside the reverse gearbox) is rubbing on the sideplate? There should be a spacer between the right sideplate jackshaft bearing and the upper drive gear. It would probably be slightly thinner than the outer spacer, and on my sled it was gold in color. Maybe look around and see if it got left out? Here's a picture showing the order the spacers and gear go in.
Hope this helps!
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