Bad vibes after head gasket replacement

[Skyboy8950]

Hello all, it has been a while (away for summer).

I replaced the head gasket on my 82' GS650GL over the summer with pretty good success. I had some vibrations afterwards that were noticable at about 4500rpm. It was suggested that I adjust the valve shims, which I did, and synch the carbs, which I did. It is still vibrating the same, but now, since I have been riding it a while like this, I notice it vibrates throughout the revs, but gets worse at 4500.

During the head gasket replacement, I had to remove the cams, timing chain, tensioner, head (of course), and carbs. I don't know what it could be. I wonder if it could be the chain tensioner? I installed it as I have read on the forums, and I heard the little "boing" as I put it in. I'm getting a little frustrated with it, because it runs really well minus the vibration, but I can't get it over 4500 without serious vibration and I don't want to damage anything.

Any suggestion would be great. Even if it is stupid, I could have done it, so shoot me anything. Thanks.

[rphillips]

Any time problems arise after having cams out, recheck to see cams are in correct time, both with each other, & with ign.

[Skyboy8950]

Could you explain this a little further? I checked and rechecked that the chain was on the cams properly as outlined in the repair manual. As with the ignition, nothing was touched with that at all. Like I said, it is running very well except this vibration. if the timing were off (say by one chain link), I would assume the bike wouldn't run as well as it is. I have a feeling that one cylinder is off somehow...

[chef1366]

If the new head gasket is thicker or you had the head machined you need to degree in the cams. This requires slotted cam sprockets, a degree wheel and a cam lobe pointer.
There is a printout degree wheel off the homepage.
It really sounds like like out of sync carbs though.

[rphillips]

When the arrows on the cam sprockets are at the exact indicated locations, the "T" mark for the ign. 1 & 4 should be at exact top center.

[Skyboy8950]

Chef,

I didn't have the head machined and I'm pretty sure the gaskets are of the same thickness. I think I do need to go back and try to sync them again. That was the first time synching them, so I may have done it a little wrong. I found that the adjustments are very finnicky.

[chef1366]

See here for the tool to help sync those carbies. I believe Motionpro makes it.

[t3rmin]

My 650 had vibes so bad I sold it. Came in around 4-5k. Bike ran like a scalded cat but the vibes were killing me. I tried everything. I hope you have better luck!

[Skyboy8950]

Thanks t3rmin,

It just started after this head gasket replacement, so I hope I can fix it.

Chef,

I bought the Carbtune that so many people on this forum recommend. It worked great and I thought I did everything right. I'll try again, maybe this weekend.

[t3rmin]

Try monkeying with how much vacuum difference you have between the inner and outer cyls. Try nearly flat, up to 1.5-2 inches difference and see where it's smoothest. When syncing my 750 I discovered the inside/outside differential seemed to have an effect on the vibes.

Another thing I did on the 750 was install permanent taps on the intake sync ports, when ran vacuum tubing between 1&4 and 2&3. That seemed to smooth it out a bit.

I also mounted the sync gauges to the handlebars and went for a ride, and discovered the vacuum under load was a bit different, and tried to account for that.

[Skyboy8950]

New Information

Hey guys,

So after posting this twice, I started to think about what I touched when I changed the head gasket. I checked the cam chain tensioner: good! I then was running it and heard the right side make a little bit of a different noise then the left; kinda a rattle. During this running, I revved it and put my hand on the engine to feel the vibration, but there was NO vibration from the engine!!! I then felt the exhaust. YES, vibration. I turned it off and smacked the muffler a little. The left side did nothing, the right side went, "twang, boing, etc." I think when I had the exhaust on the ground, under my bike for a few weeks (outside by the way), something may have fallen in there and is rattling around. This could explain the vibrations.

I'm still not sure, so with the first person who says they might agree with me, I will go outside and take the exhaust off and try to fish out anything that might be in there.

Also, could it just be a blown muffler? Do they wear out? I find it funny, though, that this started when I replaced my head gasket. It had to be something at that time.

Thanks for helping all!

[t3rmin]

Sounds reasonable. Is the kickstand or something vibrating against it? Are the hanger brackets and head bolts tight? Are the crossover clamps and gaskets as they should be?

You can use a flatheat screwdriver up to your ear to hunt for sounds. Put the tip on something solid and it'll transmit the localized sound to your ear.

[Skyboy8950]

Ok, haven't done the exhaust thing yet, but I highly doubt that is the problem now. I revved it up to 7k and the exhaust was vibrating just as much as everything else. Here is something else I noticed while riding. Lets say I get it to 6k and let off the gas. As I coast, the wheel spinning the engine, I still get the vibrations. This may be a clue to something, but I don't know what. Is something loose in there? Do I have something in the oil bouncing around? What the heck is going on?

Finally, is it worth taking it into a shop? Am I going to spend 8 hours of labor bills just to diagnose it?

FRUSTRATION!!!

Very sad gs owner

[t3rmin]

I dunno man, it seems like some GSs are more buzzy than others. In my experience the 16 valve motors are smoother. But on the other hand, my buddy's 1100 8v is very smooth...

I know your frustration very well. Have you tried the tips I gave earlier? Couple all of that with bar ends or lead weight in the handlebars and big rubbery grips and it's usually bearable.

One other thing to check is the preload on your steering head bearing. I noticed the vibes were worse when the steering was looser. I adjust my steering head so there is slight resistance when you let the bars fall to one side (while on the center stand). It shouldn't just flop to one side willy-nilly, but have an ever-so-slight drag as it falls.

[Skyboy8950]

My frustration is that this whole damned thing started with the head gasket replacement. It was all good until then, but I f-ed something up and don't know what it is. It has to be something in there. I might just tear it down (ie take the cam cover off) and look at everything again, change the oil, re-sync it, and go from there.