GN400 weirdness

[.Chris.]

Haven't been on this site in a very long time, but...

I've recently put an '82 GN400 back on the road (which had been stored for a decade), and it passed its MOT with no problems a couple of weeks ago. However riding it turns up a bit of a problem. The bike seems to wonder and is hard to keep in a straight line. You can't really relax very well when riding it. The handling is OK, but I haven't pushed it that hard.

At the MOT, the tester remarked that the wheel alignment was slightly out (although not enough to warrant an advisory), and recommended a half-turn adjustment to one side which I duly made. However this didn't appear to make any difference, so I started again by winding the adjusters all the way in, and working out with equal numbers of turns either side. No difference.

By this time I'd used the bike a bit, and had noticed that the chain seemed to have got tighter in use, so decided to give it a 24-hour soak in engine oil. This seems to have cured the tightening problem, but hasn't cured the wobblyness.

I've also noticed a slightly odd thing that's possibly related - when the rear wheel spindle is tightened up, the chain seems to tighten quite a bit, and the whole swingarm is compressed by a good few mm. However all the wheel spacers are (to my knowledge) in place.

The swingarm bearings don't have any play in them, the headstock and wheel bearings likewise. Tyres are inflated according to the sticker on the rear mudguard (25psi front, 28psi rear).

Any suggestions?
____________________
Chris
1985 Kawasaki Z550F

[Tristan.]