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Just came off, chain seized on GS550, need advice

  • Thread starter Thread starter fossicker
  • Start date Start date
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fossicker

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So I just came off my 1980 GS550 an hour ago. I was able to arrange a lowside, I tore up my armor and bent the bars, scraped the left side engine cover, dinged a silencer, abraded my new grips (dammit) and got a little road rash. In the first 5 seconds of my dilemma it sounded like the chain was skipping teeth or the trans was grinding, then the chain seized and the rear wheel locked at 40mph, I de-clutched but no joy, I jammed down on the shifter to no avail, and skidded down the breakdown lane before a barrier appeared and I decided to dismount. I rolled for a bit and immediately picked up the bike, worried about it not me! After I checked myself and the bike, catching my breath, I managed to drive it home at 10mph. And nobody stopped for me, how lovely, frakking cagers drove around me! After a cigarette I started tearing off the front sprocket cover. What I found was that the front sprocket nut is loose, I can turn it with my fingers in the confines of the bentover lock washer. Also, I discovered that the rear sprocket nuts aren't tight enough to prohibit sprocket movement, I can move the rear sprocket .5 inch forward/backward before the rear wheel moves. According to my Clymer, front and rear sprocket nuts are supposed to be torqued quite well.

Have I found the problem? I just got the bike 2 months ago and the PO said he had just replaced the chain and back sprocket, wanting less revs on the highway. I thought I checked everything over, but I missed the loose sprocket nuts. It's either that or the final drive is frigged up.

Thanks for your advice.

K.
 
Glad to here that you are OK. It does not surprise me that the cages had 'no time for you' as that is the general rule if you're on a bike. As far as the sprockets are concerned...it sounds like the PO was a poor wrench at best. Locktite is your friend on sprockets. I wouldn't install sprockets without it. :o
 
AT least your get off wasn't bad. The fact that you rode it home? Would make me question weather the output shaft bearing seized up and not the chain? May be more to it than the loose bolts

Anything chewed up near the chain?
 
Thanks for your concern. I am sore but fine, the only sympathy I get is from strangers online! I have a strong feeling that the rear sprocket bolt holes are now oval given the freeplay One thing to mention is that I could feel the grinding in the shift lever. I heard the grinding first, de-clutched, and put my foot down hard on the shift lever after I realized the clutch wasn't helping. I could feel the grinding associated with the noise in the shift lever, but that's not surprising given the proximity of the shift rod to the chain and front sprocket.
Hmmm...makes me not want to take it out again until I suss it out for good (or sell the damn thing for scrap).


Thanks.

K
 
Glad you're ok.
The rear sprocket hub has rubber dampeners that may be bad.
 
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Damned, I am glad you are ok. Wow, close one. Put it up on the center stand and put it neutral. You should be able to tell right away if something seized up. Hopefully it is just the back sprocket. I would just get another one, locktite it, and be done with it. I noticed on my bike that it has a master link on the chain. I have read that this isn't the best way to go, so I should probably replace my chain and sprockets.
 
Pls look at my video of chain movement...

Pls look at my video of chain movement...

http://www.opsimath.org/GS550/chainvid.mpg

I'm sore today -- bruises appearing on arm and leg. Here's a video of the bike on the stand, running through 1st and 2nd observing the chain, after cleaning and tightening sprocket nuts front and rear. The mpg is viewable in VLC, Media Player Classic, mPlayer, etc. Is that hop acceptable? The O-ring chain, which seems new short, is not one piece, there is a visible master link.

http://www.opsimath.org/GS550/chainvid.mpg

Given that de-clutching didn't unlock the rear wheel during the skid, the problem is either with the chain, sprockets, and/or the final drive. I examined the shaft on which the front sprocket resides and it is both clean and tight on all axes.

The front sprocket was removed and examined carefully, I found no undercutting or chatter marks, it looked pristine. The front sprocket shaft is very tight, no play in any direction, and the final drive is very quiet with no discernible vibrations.The O-ring chain is relatively new but there is a master link visible. The rear wheel/axle adjustments indicate a reasonably short chain.

There was much greasy crud full of coarse road dirt (not metal bits) built up behind the cover, easily 3/4" thick. I cleaned the whole mess with my favorite de-greaser = biodiesel (methy or ethyl ester). The back sprocket bolt holes are quite round.

Advice would be appreciated. I took the bike out for a spin up to 30mph and ran up and down the gears, it shifts beautifully, but I am very tentative.

K
 
mpg uploading

mpg uploading

The mpg is uploading now. Please try again later. 170mb mpg, broadband only. Thanks.
 
smaller vid now ready : pls watch chain hop

smaller vid now ready : pls watch chain hop

My apologies, the original vid at
http://www.opsimath.org/GS550/chainvid.mpg
is rather large at 170MB with sound. If that's too big
for your connection,

I've uploaded a smaller version, 14MB without sound:

http://www.opsimath.org/GS550/chainvidsmall.mp4

Will play in VLC, mPlayer, and DirectShow players like Media Player Classic and DivX Player and QuickTime Player.

I am revving the bike from 1200rpm tickover to 2500rpm in 1st and 2nd gear, technically the sound isn't necessary to consider the way the chain is moving around.

Regards,

K.
 
I would inspect EVERYTHING driveline related again, check your brake system as well. Your rear brake could be dragging, and when it gets hot enough, locking the wheel up. Believe me, ive done it, its tough to notice right off if youre rowing thru the gears out in the country and dont have to back off the throttle. When rolling the rear wheel by hand, the chain should spin freely, make no noise or binding. Above all, i would simply replace the chain and sprockets before I continued to ride it. 140ish bucks for a new 530 chain and sprockets from Z1
 
Did you replace the chain and sprockets?? I know you're prolly tight on cash, but they're not a forever thing..its not a shafty!! :D They generally need changed anywhere between 10-20K depending on how abusive you are, and how religious about cleaning and lubing you arre. NOT doing so can have DEADLY results, as you probably have gathered thru your little experience. You CAN put the bike up on the centerstand and run it thru the gears. It may not tell you much, since there is no load on it, but if its a chain thing, it might show you...
 
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