Wobbly wheel and changing chain tension on a GS500 - ideas?

[GirchyGirchy]

Hi everyone,

I have a friend who (I hope) is going to be selling me his '92 Suzuki GS500 later this year. This was his first bike, and he's wanting to upgrade. I am currently not a rider, but am wanting to become one, and think this would be a decent first bike. The first owner, also a friend of ours, laid it down a couple of times, so it's not the prettiest bike. But it seems mechanically sound, and doens't have too many miles on it.

He was wondering about a couple of things with the bike, that I could not answer. The first is that when travelling at interstate speeds, he said that if he were to take his hands off, the front will start oscillating. It's not a good idea to remove one's hands anyway, but he didn't know if that was a sign of some problem or not. I asked a rider here at work about it, and he said that this is actually pretty common, and could be a number of things. Any suggestions? Is this something to be concerned about?

The other thing he mentioned was the chain tension - it seems to become tight/loose/tight as the wheel turns. I'm an avid bicyclist and work on my bikes, and I see that happen sometimes - on bikes it occurs when either the chainring or rear cog is eccentric on the shaft, so as the cranks or rear wheel rotate, the gear wobbles. This changes the chain tension - it becomes loose when the gear is closer to the other gear, and the chain tightens as the gear rotates further away. Does this happen with motorcycle gears, too? Would I just need to replace the gears and chain?

Are there any issues I may also want to look out for, either in general or specific to the GS500?

Any help would be appreciated! I'm excited about this bike, as un-pretty as it is, and am looking forward to riding. Thanks for any suggestions.

Brian

[telefunkin]

The other thing he mentioned was the chain tension - it seems to become tight/loose/tight as the wheel turns.

Sounds like the rear wheel is out of alignment. There should be marks just above the axle bolt on each side of the frame(check the link below for a pic). Check these to see if the axle bolt is lined up to the same mark on the opposite side. If it's out of alignment, the wheel will be angled to one side. I'm not sure, but that's possibly causing the speed wobbles too.

[telefunkin]

oops, here's that link I mentioned

http://www.dansmc.com/rear_wheel6.JPG

[BuzZz]

If the sprockets are actually true and concentric, then the rear wheel bearings may be toast. The oscillating bars could also be caused by this.

It is also possible to stretch only part of a chain (like high RPM clutch dumps on a lower powered bike that won't break the tire loose), and that could cause varying tension.

[Shorts]

On the front, the wobbly could be simply old tires or unbalanced tires. But do check the bearing in the front wheel and in the steering head.

[crazypj]

Common problem after rear tyre change is the spacer left out/missing from sprocket carrier bearing. Its impossible to torque rear axle as the bearing is taking all the side loading. Chain is probably scrap. If wrong size tyre is fitted to front it makes it wobble but its more likely that steering bearings are notched in centre position.
You need someone who knows what to look for go over bike.
I was a Ministry Of transport (MOT) vehicle inspector in Britain for several years.
GS 500 is a very reliable engine with reasonable chassis/steering.
Easy to service with shim over bucket valve adjustment (no need to remove cams) Only issue with servicing is techs turn them over without removing spark plugs and shear the timing pin on crank end.
PJ

[flynrider]

The chain is worn. They tend to wear unevenly when they get to the end of their lives, or if they have not been properly lubed. What you're seeing (assuming the back wheel is true) is some of the rollers binding as the chain goes around. Since a worn chain will also put abnormal wear on the sprockets, check those too. If the teeth are pointed (should be flat topped) or angled, then they should also be swapped out.

[GirchyGirchy]

Thanks for all of the replies, everyone. If/when I get the bike, I'll take it in and have someone look at it, just to be safe. But it sounds like most of the thoughts center on the bearings.

As for alignment, he mentioned he has had the rear aligned, so it should be ok, in theory.

The chain being worn in one spot might be true - I'm not used to that. I am, however, used to checking for shark teeth on the sprockets, so I'll make sure to look at that.

Turns out he had mentioned the bike to someone else who might be interested, so I'm second on the list. But if I end up with it, I might post some more after getting it looked at.

I'll likely get a service manual, but can anyone recommend a good general repair manual for bikes which deals with a lot of common items, such as bearings?

Thanks!