Motorcycle Repair: 92 fxlr vibration, wheel bearings, pivot shaft

Question
Mike,
My lowrider has a vibration that has our local shops stumped. She has a Bad vibration in the lower engine/drivetrain. It happens just above idle with RPM's going up or down near idle (bike can be sitting still or driving in any gear.)We installed new plugs,coil,neck bearings motor mounts(front and top)wheel bearings, tires.We also retorqued the swingarm pivot shaft to 48 ft lbs. The carb was cleaned and the bike was tuned and dyno'd. The shops also pulled and inspected the clutch assembly. The primary chain slack was measured and is within 1/32" all the way around. We inspected the frame for engine to frame contact (bolt,rock etc.)The bike has an fxrs gas tank on it, but I can't see any contact marks. My next step is to pull the compensating sprocket and inspect it. There was a slight vib. when I got the bike, but it got worse when a shop installed the front motor mount (mount is installed right and is new and correct.)
Also can you explain why when the motor is lifted about an inch to pull the front motor mount I get streams of little air bubbles going from the carb up into my in-line fuel filter?
Thanks alot for any help you can give me.


Answer
Check the compensator like you were planing on. It might be there.
On the air bubbles, never heard of suck a thing and not sure why it does it, unless it haas to do wht he changing of the angle of the motor when you lift it and it is releaving the air in the carb.
Good luck and happy riding
Mike