I would take care of the worn out components ( replaced what’s broken or bad first )
Then move on to the chain issue, you may have a bad engine sprocket and a bad rear sprocket as well.
Take a close look at your engine sprocket, and look for possible sharp edges, uneven teeth, etc ( a bad engine sprocket can ruin a new chain and rear sprocket at no time )
You may have to replace engine sprocket/driver, rear sprocket and chain altogether
Depending on the engine and clutch set up you’re running, some like it at 1/2 inch of play, some at 1 inch of play, etc. Too loose or too tight of a chain will kill the whole thing, including your engine driver.
Make sure you check your chain tension, lube your chain and driver inner bushing in every practice session.
Hope that helps, my 2 cents.
November 15-19, 2017
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