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Discussion Starter · #1 ·
Hi

After pulling the head to replace the cam chain guide I have very unstable revs, jumping from 1200rpm at idle to 2000+
And back down. If I increase the revs the problem is reduced but it's still present.
First:
I checked carbs for air leaks on the intake boots with spray - No change
Pulled carbs and cleaned - No change
Check spark on plugs, looked good - No change
Valve gaps checked - no change

I used a strobe light to check timing and the "Advanced marks" are showing on the flash
of the strobe (Idle) rather then the "F" mark.

Flywheel.jpg


Could this be the cam chain being placed on an incorrect tooth of the cam cog?
I checked and double checked the placement of the chain when I installed it and lined the marks
parallel with the head casing as per manual but I guess I could have stuffed it.
Possible CDI malfunction?

I will run through the sticky on electrical diagnosis resistance checks to see if anything shows up.

Thanks!
 

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The ignition timing on these bikes is independent of the cam timing. The key that indexes the flywheel to the crankshaft may have sheared allowing the flywheel to rotate out of alignment. There is a tool available to remove the flywheel:

https://www.motionpro.com/product/08-0085

Or you can get a 20mm bolt with 1.5 pitch threads and do the same thing.
 

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It shouldn't matter if the key was off, the ignition is triggered by a magnet in the flywheel. Sounds more like a fault in the wiring or the ignition control box.
 

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It shouldn't matter if the key was off, the ignition is triggered by a magnet in the flywheel. Sounds more like a fault in the wiring or the ignition control box.
Actually the woodruff key in question positions the rotor to the crank and that sets the rotor magnet position in relation to the pickup.
Quick check for positioning would be to remove a sparkplug and insert a straw or something flexible to rest on the piston, rotate the engine until the straw stops rising. The rotor should be at or very close to the T mark.
 

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Those numbers are close enough that the system should be operating close to proper. Check that your timing light doesn't have an advance degree wheel, if it does be sure to turn it off or use one w/o that "feature", and recheck the timing again. If it's still off then the CDI unit is bad.
 
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