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Posted

I'm trying to fix a 1986 Yamaha yfm80. I suspect that the CDI is bad since I get spark but my timing is 60 degrees advanced, I  can't find a new or reasonably priced used CDI. I was wondering if anyone knows of an alternative CDI that would work? If a CDI from a later year YFM80 could be spliced into the ATV or perhaps from different Make/model ? that would produce the correct timing for this engine

Posted

There will be plenty that would work if you are willing to modify the wiring like that... There will be plenty too that won't work.

Are you sure that timing isn't because the flywheel key has sheared ? If the trigger coil is mounted too close too they also get a bit advanced, but not generally that much. If it's still got a good spark I'd be checking in the flywheel. Someone might have moved the charge coils, key's broken, trigger coils mounted too close or in the wrong place... Maybe. 

Some parts places have a feature where if you look up a part, they will tell you what other models that part fits. You might be able to use a genuine cdi off a later model, or, find an aftermarket part that fits that later model the parts list says is compatible...

Posted

Thanks Mech for taking the time to reply. Your suggestions are all very good and relevant. The Magneto keyway is intact and possitioned correctly, the valve sprocket is also correctly aligned, the reluctor gap is correct (.028). The spark jumps the .028 gap on the plug. When I crank the engine with the timing light connected I'm seeing that the timing is advanced by 60 degrees. I've ordered a motorcycle CDI from eBay the seller states that it will work on this engine. I'm hopeful that after I splice it into the harness that it will correct the timing issue, but am sceptical. I was wondering if other people have experienced this part shortage issue and how they solved this problem.

Posted

I received this YFM80 ATV in a no run condition, so it's possible that incorrect parts are responsible for this problem? Before I search for other causes l want to install the eBay replacement CDI  (being shipped from China). Thanks for the useful ideas I will research these suggestions in the event that the new CDI doesn't resolve this issue.

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