I had that problem. Just by coincidence I had to change the grips and the problem dissapeard.

 

I thought that it was the drive chain as well, so, I replaced the chain and sprockets and the back tire but it hasn't helped. I am going to put it in the shop next wednesday so If they fix it I'll pass on the word as to what needed to be done.

 

I think that crucialfate and I may have the same issue, but diffferent from some others in this post. I noticed, crucial, that you used the word "rattle". That would describe what I'm hearing, but it's not a "vibration". It's much like the typewriter sound on warm-up, but it doesn't go away. It just rattles at low rpms in first and a little bit of second, or when I'm stopped at a light or something.
I was riding with some guys the other day, we were sitting at a light, and I yelled over to my buddy "Do you hear that, man? Do you hear that rattle?" He replied with " You know there's something wrong with your bike when it doesn't rattle."
Not the answer I was looking for.

 

Yesterday I've tried to adjust the balancer shaft. I removed the clamp pinch bolt, then tried to rotate the shaft anticlockwise, and noticed, that it doesn't stop, as it should do.. [&:] I could turn it as many times as I want. The same thing when rotating it clockwise. DOES IT MEAN, THAT BALANCER HAS BEEN REMOVED?? OR SOMETHING IS BROKEN?

 

That's not really supposed to be messed with other than after a teardown, technically. Although, people do check them.

At the tightest extreme is there even any resistance? That resistance should be considered the stop, and back off one mark from there. It's an eccentric and may be just at the tight point going over the top. If you noted the original mark before to move it you could return it there OR, back one off of the tightest mark. That will assure that you're not too tight. This is one where too loose is safer than too tight.

 

As Dad says, the balancer shaft is something generally fiddled with only on a tear down. But - my bike developed a vibration that would numb hands in just a few miles. Setting the gear lash took care of things. After turning it counter-clockwise for a full turn and finding no resistance, I went back clockwise to 1/2 half mark past the original index mark. That quieted things down. Consecutive clockwise turns of 1/2 index mark showed the vibration lessening progressively until it was gone. At that point, however, a high pitched whine became evident, indicating things were too tight. The shaft was then turned counter-clockwise in 1/4 index increments until the whine disappeared, and then 1/4 mark further for safety. There is a small amount of vibration around 5,000 rpm, probably a natural resonance point, but it's smooth above and below that point.

 

thanks, m8s I'll consider the tightest point as a stop.

 

I have the same rattle. I was told by the guy who sold it to me, that it was the starter chain, but I'm more concerned about it being the cam-chain. The trouble is, because of the open chain shaft in the center of the engine, any sound that might be from lower down, can reverberate up into the nice accoustic chamber that is the air space under your cam cover, since the sump is mainly full of oil and doesn't resonate sound too well.... Does the screwdriver stethoscope method still work to pinpoint the source of the sound in this case? Question about Cam-Chain rattel noise. Does that occur at all RPMs?? (i.e. is this rattle at low rpms likely something unrelated since it disappears at higher rpms)....... ????

 

After the shop checked it out, they found that the valves were far out of adjustment. I had never adjusted them and it seems as if the previous owner had not had them done either! When they did a compression test they found cylinders 1,3,4 had 140psi but cylinder #2 only was getting 90. Now it has 140 on all cylinders. They also found that I had a clogged jet on the #1 carburator. When they pulled the carbs there were some small beads similar to the beads on the end of a plastic hairbrush bristle in the bowls. He said they have seen this recently on several other bikes, but didn't know what could be causing it. Has anyone else ever seen or heard of this? New fuel formulation?

 

Just had the carbs on my '91 apart, they were clean as a whistle except for #1. That had the tiniest bit of dirt in the bowl. The filter was gunked up. Some crud up in the main jet. No lilttle hair brush ***** though. That's a new one on me.