Motorcycle Repair: 1978 Yamaha XS400, rear wheel bearings, chain and sprockets

Question
Hello Chris.
I own a 1978 Yamaha XS400 with about 32,000 on the clock and cast aluminum whells , no wires spokes, only had it a short time and I am a novice rider. The bike seems fine on the road other than needing up dated on some tires and maybe chain and sprockets. What concerns me a little is the bike has a weird tendency to wibble wobble on lock to lock low speed turns, like say in parking lots or doing a sinlge lane U-turn, while in first gear but kinda lugging the motor but not too hard. Is this normal?
Thaks for your time.
Mark P.

Answer
Hi Mark.
 Considering that the balancing act of doing a pin turn is tricky, the first thing is to determine if it's nervous twitching in your muscles (as you make micro-adjustments to your steering and throttle) or if it is elsewhere.

To find out if it's in either the bearings or steering head, the big indicator is if it happens at ANY other time, including high speed straights.  If you feel a wobble of any kind, consistently in your handlebars, then there could be a problem.

1) Put the bike on the centerstand.

2) Wiggle the rear wheel.  If it shifts on the shaft, the rear wheel bearings are needing replacement.  If the swingarm does the same thing, then the swingarm bushings need replacement.

3) Raise the front wheel off the ground.  Lock the steering and wiggle the front wheel. If it moves as described for the rear wheel, the bearings need to be replaced.

4) Unlock the steering and hold the front wheel between your legs and try to move the handlebars left-right and front-back.  If it moves in the steering head, replace the steering head bearings.

If nothing is loose, then the problem is related to muscle movement and the only cure is the same thing that gets you to Carnegie Hall;  Practice, practice, practice.

Good luck.
FALCON