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Lots of vibration, any ideas why?

  • Thread starter Thread starter Anonymous
  • Start date Start date
I slid some rubber in between the slip-on and the rear exhaust mount a while ago. It made no difference with the vibration.

I haven't ruled out the slip-ons as the source of the vibration as I think they're pretty low quality even though they're only a year old.

I put the bike on the centerstand and reved it to 3000 RPM in gear. The vibration was still there but the rear wheel and rotor ran perfectly true.

I am certain now that the vibration is caused by the engine or possibly the exhaust.
 
Grab some old kitchen oven mitts from the missus and do the centerstand trick again. This time have someone grab the exhaust pipes (wearing the mitts of course) to see if you notice a change in the amount of vibes.
 
I am slowly going insane!!
Its been several months now and I can't determine the cause of these vibrations. If they had always been there I would understand and claim that the bike simply vibrates, but this only started this summer some time.

I have checked everything I can easily get at. If the problem is internal, it will remain that way until the engine blows up and I am forced to rebuild.

I have now checked everything electrical to make sure each cylinder is running equally. (ie. spark, ignition, plugs, wires, boots, timing advancer, etc)

I have loosened and re-tourqued to spec. all engine mount, cylinder head and cylinder head cover bolts, as well as many others.

After the engine is hot, I've checked my spark plugs and they are a very light tan color, with cyl. no's 1 & 4 appearing to be slightly leaner than no's 2 & 3. This seems okay.

When I rev it to 3,500 rpm and feel around various points on the bike, the mufflers and rear pegs(where the mufflers attach) seem to vibrate the most. It is possible that the vibration may migrate back from another area to the mufflers, but I think my next step is to try and find a stock exhaust system to swap in.

I've tried inserting rubber spacers in a few mounting locations, but it does very little if anything to help.

Like I said before the carbs were cleaned and sync'd and the cam chain adjuster checked.

I guess I am looking for someone with the exact same experience who has found a solution. I NEED TO FIGURE THIS OUT!!

I'll go back to banging my head against the wall now.
 
My bike vibrates so much my mirrors are useless! But I guess I would be going crazy with it if the bike wasn't always that bad. Anyway, I'm pretty certain that my bike is noisy and vibes alot due to worn cam chain guides. Not sure if this is my problem let alone yours, but it may be something to investigate?? Good luck.
 
Vibrations

Vibrations

My GS850 does this about 3-4K, my Kaw KZ900 does this about 3-4K, the Sportster I had did it about 600-4K! I'll take the buzz of Japanese over the constant vibes from a Sportster. It's the nature of the beast. But on the off-chance you find the culprit please let us know so my right hand will stop falling asleep :lol: Bob
 
Most Jap four cylinders were known to vibrate between 3-5000 rpm, however as I understand your bike has got worse since fitting aftermarket exhausts? have you tried finding a quiet bit of road and removing the mufflers (temporarily) to see if it has any effect? this should allow you to work out if it is exhaust related. I would not ride it any further than you have to without the mufflers as it will be running very lean.
Dink
 
There are universal joints on the shaft in your swingarm. If one of these "froze" it may produce vibration.
 
I did try removing the mufflers and went for a very short ride being too scared to run without them. It was very difficult to tell if the vibration was gone because of the very loud rumbling of the bike running with no mufflers.

I passed up on buying a complete exhaust system on ebay last night from another '81 650. I would love to get a hold of a completely stock exhaust for about an hour just to test it. Hard to come by though.

I might be barking up the wrong tree with the exhaust lead, but I would like to eliminate it.

Thanks again for everyone's input.
 
I was out riding the bike around the city yesterday and stopped at a aftermarket bike/sled shop that sells parts and work on sleds and bikes.

I began talking with the owner who works on all makes of bikes. I told him about the vibration problem at that 3,500 rpm range. He immediately suggested crank bearings, being that the problem seemed to be isolated to the engine. (I think someone on here suggested that) He also suggested connecting rod bearings, but the crank seems more plausible, either way it looks as though I'll have to make a decision this fall whether or not to tear down the engine.

If there is a bearing going, once it fails, the damage will be more costly than the replacement of the bearings so the decision is fairly easy.

I do have the factory and Clymer service manuals, so I think I'll try the work myself and take my time.
 
Before you get into opening the engine try a simple check on it.

If you have a mechanic's stethoscope, this is the time to use it. If not, get a broom handle or a piece of thick wood dowel. Do NOT use anything of a half inch or smaller diameter as it may damage your ear. Cut the length down to suit yourself. Put one end on the engine, and the other against your ear and listen.....works just like a stethoscope, but not as comfortable.

Check out the engine and try to identify the various noises it makes, placing the tip at various points on the engine and transmission cases. Once you have a good idea of the noises, run the revs up a bit.....just a bit...500 more than idle....and listen again. Then run it up to 3000 plus.

These engines have roller bearings, and I have not yet heard one of them going bad, so I cannot describe the sound. In plain-bearing engines, you would hear a distinctive thump from a bad main bearing, and the work "knock" is appropriate for connecting rod bearings.
 
I'm pretty sure that the GS650 has plain bearings.

Bad main or rod bearings seem very unlikely without noticeable nasty sounds. Also, there should be a metalic indication in the oil. There are some services that will analyze your oil and tell you with a high probability what is the problem. I would definitely do this before tearing down your motor.
 
There certainly is no visual indication of metal in the oil. I've changed the oil twice this summer and there's nothing on the plug and it looks used, but clean in the pan.

There has been no change in engine sound since I've had the bike.

I am convinced that the vibration is not normal, and has gotten worse this summer.

If the problem is not internal to the engine, then I am at a loss.

With the bike on the stand, I can start it(in neutral, of course) rev it too 3,500 rpm and feel the vibration immediately. This, to me, eliminates anything to do with the chassis, driveline or transmission.

The problem must be linked to the engine or possibly the exhaust.

I know this bike may never be vibration free, but I know it can be better than this.

I am going to get a hold of a timing light and check ignition timing, maybe check the valve clearances again and re-sync the carbs.

Thank you all again for helping to try and solve this dilemma and save me some time and money in the process.
 
I believe you said that you had replaced the exhaust system with an aftermarket set. Considering all you have checked and the running test on the centerstand to find the vibration is not drivetrain, I agree that it is an engine problem. Also, as said, bad bearings etc., woul leave metal filings in the oil and you have none. My hunch is that the vibration is a result of the exhaust pulse resonance/phasing of the replacement muffler and header system. When the exhaust resonance wave from an engine is in alignment with the time,velocity and flow characteristics of a muffler system, it is said to be in "tune". I suspect that for whatever reason, your particular exhaust is close to 180 deg out of phase for the engine to breath correctly and that pressure wave is arriving back at the exhaust port just as the exhaust is trying to expel burnt gases. It would be something like two hammers meeting everytime the exhaust opens. If you still have the original exhaust (that apparently did not give this problem), I would reinstall it to see if the problem disappears. (just my theory and I'm sticking to it) :-)

Earl


Duke said:
There has been no change in engine sound since I've had the bike.

I am convinced that the vibration is not normal, and has gotten worse this summer.

If the problem is not internal to the engine, then I am at a loss.

With the bike on the stand, I can start it(in neutral, of course) rev it too 3,500 rpm and feel the vibration immediately. This, to me, eliminates anything to do with the chassis, driveline or transmission.

The problem must be linked to the engine or possibly the exhaust.
Click to expand...
 
out of curiousity, are you talking about a buzzing vibration, or a very noticeable shaking?

my bike has a pretty constant buzz through out...probably due to the exhaust and some engine mount modifications. the carbs were sync'ed last weekend, and from what i can feel, it had no affect on the vibration.

i am trying new grips which i ordered this week.

what i suggest you try next is adding weight to the handlebars. people suggest using sand, bb's, or any other dense object that you can fit into the bar ends. you'll have to plug the ends afterwards.

sure hope you get it figured out soon.

~Adam
 
It is definitely a buzzing vibration I feel more in the seat and pegs than the bars. I did put a new set of foam grips on this summer which may have helped minimally.

I wish I had a stock exhaust system to try out. I threw away the original mufflers right after I got the bike. They had large holes rusted through both of them. I replaced them with Lu Hao Silencers Ltd. $60 slip-ons using the existing header pipes which are in excellent condition. I had to cut the mufflers off right behind the pegs.

Maybe if I could convince my local bike parts shop to loan me a new set of "better" slip-ons to try around the block, I would be able to tell right away if there was an improvement.
 
i believe GS550 exhaust will fit the 650...not sure about the years though. if you can swap mufflers easy, try that.

you're still running the stock exhaust headers though, right? have you verified they are tightened good to the head?

i've gotten used to the buzzing in mine...its not too bad. hopefully the grips will make it a lot more tolerable...i'm going to see what i can add into the bars weight wise when i swap grips.

you should try the same maybe. as for the buzzing in your seat...how do the bushing under your seat look? make sure your fuel tank is bolted tightely in...and it 'should' have a rubber bushing on its bolt as well...to help reduce vibration.

~Adam
 
I have the stock header pipes on the bike. I have checked the mounting bolts and they're snug.

There are rubber bushings on the 2 bolts for the gas tank. There are also 4 rubber spacers attached under the seat which appear to be in good condition.

The rubber bushings for the pegs are still there. They could possibly use replacing, but they're there.
 
i think you just might have the same buzz as me. you may want to look into adding some weight to the handlebars and see how it helps your hands.

~Adam
 
BZZZZzzzzz!!!!!!

BZZZZzzzzz!!!!!!

Duke:
Heres one that has not been mentioned and I have heard of it happen to our style motors. As you know, our motors are a pressed fit built up type of crankshaft. More to the point , the crank is pressed together out of several pieces. I have heard of these motors 'twisting' the crank, the upshot being the cranks are no longer truly balanced with alot of vibration as a result. This is why the cranks were welded up on the 83 and up 1100s' & 1150s'. Just another tidbit of info, but it seems to be narrowing down to this.
Rick.......
 
being one who has twisted a crank GS1000 years ago it puts a vib through the whole bike. rear veiw mirrors became useless above 3000 rpm footpegs vibrating rear end going numb(rider that is) even had a few bolts come loose that don't normally. sounds familiar don't it.mine was caused by the fact i put a 1080 kit and a heap of mods in ,went dragging only did 3 runs before the vib arrived .have heard of a few stockers doing it.. good luck ozman
 
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