Weird vibration 81750e.

[arveejay]

The bike I recently purchased has had some changes made and I'm trying to track down a vibration. The rear shocks are too short and bottom out easily, the bike on the center stand has the real wheel touching the ground, I think the front suspension has been changed as there is a stabilizer between the shocks and they are all but bottomed out so that you can use the center stand. At about 45-50 mph I get a vibration that feels like chain and sprocket meshing. It also feels like it could be rear wheel bearings. I've felt it down to 40 mph and it disappears at about 55. At 50 mph if given any acceleration the vibration goes away. I'm going to pull the wheels and check the bearings but wondered if anybody had an opinion. The carbs were syncd and are pretty much level to each other at 2500 RPM.

[kahuna]

bad vibes

check the tension on your chain,lube it,then make sure your rear wheel is
properly alligned using the notch lines on each side of the swing arm ensuring they are identically placed.Hopefully the easiest thing to do first works.

[crc1214]

If it doesn't increase as speed goes up, I'd almost lean toward worn or mis-adjusted/un-lubricated steering stem bearings.

Do your bars shake quite a bit when you let your hands off of them at this speed range?

If you also tend to pull to one side during braking, I would suspect the swing arm bearings as part of the cause or all of the cause.

Good idea of course to check the chain/sprocket lubrication/tension/alignment and the wheel bearings as well though.

Good luck. Tracking wierd vibrations and shakes down can be a real bear, but we'll get you through it.

[arveejay]

It runs smooth, it doesn't pull either way when braking, front end seems fine. Havn't checked with no hands yet but I hold on loose and comfortable and it feels true. I was suspecting swing arm bearings but I or wheel bearings but will have to pull and check. Could swing arm bearings cause a obvious vibration like this? I did lube and adjust the chain first as I was sure it was that at first. OK Thanks for the ideas, I'll do some checking this weekend.

[kahuna]

bad vibes

when I first got my 750 she had some bad swing arm bearings.If I stood her upright holding clutch lever side of handlebars with my left hand,I could place my right hand on the seat grab bar and give it a shake.You could physically see the play in the swing arm as side to side play is supposed to be 0.I didn't have any bad vibrations, though it did make for a thrilling ride above 80.Maybe you should try to duplicate vibes with more weight on back like a passenger if it is safe enough.4 ears might also pinpoint location.
Is this the end or time for just one wheel?

[arveejay]

It feels like the chain and sprockets are having a meshing problem. I initially suspected the front sprocket was loose. Check it and is very titgh and no slop in either direction. First 3 gears are exceptionaly smooth. Motor feels nice and tight, but it does feel like it could be in trans. also. Maybe can hear valve noise also, will get gasket and check that also. I've also heard about clutch vibrations also so I've been lookingn for a manual.

[renobruce]

If you are adjusting the chain slack on the center stand, it may be too tight once on the ground. Check your chain slack while sitiing on the bike. It might be too tight.

[arveejay]

Yes, I adjusted the chain with bike on center stand. I think with the soft shocks, it may be too tight when sitting on it. I will get my neighbor to check it when I'm sitting on it. I had it on centerstand and ran it through the gears to watch the chain. It is drifting left and right and shaking a bunch. I'm pretty sure the problem lies in the chain but each roller spins freely and it appears like new. How would I tell if the right chain for the gears was used? Is it marked on the chain?

[kahuna]

bad vibes

without sitting on my bike I keep about 1 inch of play in the chain.But say again exactly what is drifting side to side and shaking alot?Noted also was your statement about soft shocks, shocks front and rear should seem firm when you push down with a fast recovery(no bounce).double check your air pessure in each front and that there is no heavy oil rigs in travel area and make sure the rear are adjusted equqlly and no damage to or looseness where each shock mounts to the bike and swing arm.Did you give the bike a shake to check swing arm bearings yet?Those will definetly give the drift feel. Suzuki says; fork air pressure 7psi use bicycle pump only,if you go 7.10 that covers air loss when you check em.to lower pressure bleed the valve.
chain play with bike on center stand 0.8-1.2in,you can clean your chain with kerosene if needed and simply lube it with straight 50 weight oil
dealer can give info on chain replacement # Gs750t calls for DAIDO D.I.D 630V or TAKASAGO RK630SO

[earlfor]

Chain dimensions are standard. A #630 chain is the same size regardless of who manufacturers it. Its not possible to install a #530 chain on #630 sprockets because #630 chain measures 3/4" pin center to pin center and #530 chain is 5/8" pin center to pin center.

The chain and sprockets feeling like they have a meshing/vibration problem is probably due to 1 of 3 things. 1. a chain that is too tight will bind and cause this. 2. the rear sprocket not in alignment with the front sprocket can cause this. 3. A worn out chain that is stretched so that the pin spacing is now greater than the required 3/4" will cause the problem. The chain stretches. The sprockets do not. LOL To check this, remove the chain, stretch it out and measure it. It its 102 links, then it should be 102 x .75" per link, or 76.5 inches long when new. If its longer than 76.75 inches due to wear/stretching, it is worn out and should be replaced. Worn chains having subsquent incorrect pin spacing are the #1 reason for worn sprockets. The #1 reason for stretched chains is overtightening. Or in other words, the #1 reason for chain and sprocket problems is Operator Error. :-) :-) :-)

Earl

How would I tell if the right chain for the gears was used? Is it marked on the chain?

[arveejay]

Re: bad vibes

without sitting on my bike I keep about 1 inch of play in the chain.But say again exactly what is drifting side to side and shaking alot?Noted also was your statement about soft shocks, shocks front and rear should seem firm when you push down with a fast recovery(no bounce).double check your air pessure in each front and that there is no heavy oil rigs in travel area and make sure the rear are adjusted equqlly and no damage to or looseness where each shock mounts to the bike and swing arm.Did you give the bike a shake to check swing arm bearings yet?Those will definetly give the drift feel. Suzuki says; fork air pressure 7psi use bicycle pump only,if you go 7.10 that covers air loss when you check em.to lower pressure bleed the valve.
chain play with bike on center stand 0.8-1.2in,you can clean your chain with kerosene if needed and simply lube it with straight 50 weight oil
dealer can give info on chain replacement # Gs750t calls for DAIDO D.I.D 630V or TAKASAGO RK630SO

The rear shocks are spongy and the bottom setting is on the tightest setting with the dial on top set at 3 with 4 the strongest. When I get on it it falls about 6 inches. They are also too short because when on the center stand the rear wheel bareley touches the ground with no weight on the bike. The drifting is describing the chain movement, it acts like the chain is too wide and has at least 1/8 inch sideways movement when on the sprocket. The front forks are 7-8 pounds and the front end feels fine. It feels like a speed vibration, because up to about 35-40 mph it's silky smooth, I was somewhat thinking 4th gear was bad or something but it does it also in 5th gear, seems like low rpm problem.

[arveejay]

Chain dimensions are standard. A #630 chain is the same size regardless of who manufacturers it. Its not possible to install a #530 chain on #630 sprockets because #630 chain measures 3/4" pin center to pin center and #530 chain is 5/8" pin center to pin center.

The chain and sprockets feeling like they have a meshing/vibration problem is probably due to 1 of 3 things. 1. a chain that is too tight will bind and cause this. 2. the rear sprocket not in alignment with the front sprocket can cause this. 3. A worn out chain that is stretched so that the pin spacing is now greater than the required 3/4" will cause the problem. The chain stretches. The sprockets do not. LOL To check this, remove the chain, stretch it out and measure it. It its 102 links, then it should be 102 x .75" per link, or 76.5 inches long when new. If its longer than 76.75 inches due to wear/stretching, it is worn out and should be replaced. Worn chains having subsquent incorrect pin spacing are the #1 reason for worn sprockets. The #1 reason for stretched chains is overtightening. Or in other words, the #1 reason for chain and sprocket problems is Operator Error. :-) :-) :-)

Earl

How would I tell if the right chain for the gears was used? Is it marked on the chain?

I think In this case it was operator error if the chain is too tight. So to remove the chain, if I can't find a master link do I need a chainbreaker if I want to salvage the chain or could I just use a whizzer and just replace the master link.? I havn't looked yet for a master link. I did eyeball the chain after tightening the bolts and locks and it looked perfect, I didn't check it while I had the cover off inspecting the sprocket for alignment but I'll try a flashlight before I take the cover off again. The info for measuring stretch is good to know. does somebody make a 630 chain that might be a little wider than standard? I'm leaning towards the too tight theory and will enlist some help checking it. With me weighing 240# and worn shocks it is probably too tight, I have bottomed the shocks on a pretty good road with a couple little dips in the road. Will compressing the rear suspension tighten the chain as a reaction?

[kahuna]

bad vibes

remove swingarm to change chain,piece of cake.I prefer continuos link.while rear end is apart clean and grease your swing arm bearings if good.new ones from dealer not to expensive and probly worth changing.Shocks can get pricey but maybe you can find a decent set at salvage.

[earlfor]

You will need a chainbreaker to break the chain. You can refit it with a clip master link, or a rivet link. There is a rivet tool made for installing a rivet link, but I have installed one without the tool. Without the tool, it is best to have a friend hold a backing block behind the link while you peen it together. A sledgehammer head makes a good backing block. :-)

edit: ............yes, you can break a chain without a chainbreaker, but my experience is that its a royal pain in the kazoo.

Uhhh, if someone made a #630 chain that was wider than standard, it would not be a #630 chain. eheheh

On my bike, I want about 3/4" slack on the chain lower run above AND below centerline, or 1 1/2" total movement when I am sitting on the bike and my weight is compressing the suspension. As the suspension compresses, the chain becomes tighter, so while its easy to set chain tension with the bike on the centerstand, it will not be the same once you're on the bike. I set my chain (with the bike on the centerstand) to about 1 1/2" of slack above and below the chain. I can move the lower run of the chain up and down a total of 3". Sitting on the bike with the bike on only its tires, suspension compression results in my having the 3/4" above and below I want. I weigh 160 lbs, so you may need to set more slack in your chain with the bike on the centerstand than I do, as compression would be greater at your weight.

Earl

I think In this case it was operator error if the chain is too tight. So to remove the chain, if I can't find a master link do I need a chainbreaker if I want to salvage the chain or could I just use a whizzer and just replace the master link.? I havn't looked yet for a master link. I did eyeball the chain after tightening the bolts and locks and it looked perfect, I didn't check it while I had the cover off inspecting the sprocket for alignment but I'll try a flashlight before I take the cover off again. The info for measuring stretch is good to know. does somebody make a 630 chain that might be a little wider than standard? I'm leaning towards the too tight theory and will enlist some help checking it. With me weighing 240# and worn shocks it is probably too tight, I have bottomed the shocks on a pretty good road with a couple little dips in the road. Will compressing the rear suspension tighten the chain as a reaction?

[arveejay]

OK, I did adjust the chain slack to about 1 1/2 inches on center stand. I will readjust with weight on bike and add more slack before I remove chain and try it this weekend. Man that would be nice if that's the problem. I'll try it and let you know what happens. Thanks for all the great advice. Though the forum has changed, the quality of the site still remains the same.