Timing causing EXCESSIVE Motor Vibrations HELP!

[DrewDidIt]

Hello,

I have a 1978 xs650 that I have been bringing back to life. I overhauled the engine with new seals and rings, cleaned and synced the carbs and she fired right up. After running perfect for 350 miles, the 10 mm nut that holds the timing advance to the rod (the one the runs through the camshaft) came loose while going 55 mph and caused havoc. As I coasted to the shoulder, there were a series of backfires.
During the event, the timing advance bracket was cracked. I replaced it with a new one (same part #) And now I'm getting alot of motor vibration. The bike seems responsive but I would be afraid to take it over 45 mph due to the excessive motor vibration. Also the points have to be ran in full advance for the rotor mark to line directly up with the F mark at 1200 rpm.

I had it running perfect and now Im at my whits end. Please help.:banghead

 

[NONclow]

From your other thread:

...It looks as if the whole timing advance unit may have rotated a bit aswell. The keeper pin for the unit i thought used to be in a different location then before. Up near the top (its near the bottom now)

Theoretically, when the adv experienced some interference the cam was still moving, therefore retarding timing, as much as 180 deg moving the spark event into the exhaust (or if long enough, the intake) stroke. I assume the "backfiring" was taking place out the exhaust?

Are you sure the advance weights are returning fully at idle, and opening fully at 3000 rpm?

Or, maybe the advance rod now has a twist to it. With both the points and advance covers off and the corresponding pins exposed, do they both point at 12 o'clock? If not, the points would need more advance to run. No repair. Just replace the rod.

My next courses of action would be to perform (or have done) a comp test, and a leak down test to see if there are any ill seating valves (from the backfires) causing an imbalance.