Vibration

[dakota450]

I have been trying to locate and repair a vibration that I am getting on my 99 standard.  It is kind of an oscillating vibration that starts around 55mph and continues and finely goes away if I get above 70-ish.  It only seems to happen in 5th gear and its worse if I am just cruising at a sustained speed between 50 & 70.  The minute I pull the clutch in, its stops.  I have had the entire drive train apart and inspected it and replaced the u-joint.  Everything is lubed properly and looks perfect.  The bike has 45k on it and an Avon Cobra with about 10k miles on it.  The pipes were cut and drilled by the previous owner.  I have had this bike for about 3 years and thought it was normal until my son bought the exact same bike with more miles on it and I rode it.  I has factory pipes and is smooth as glass.  Now this vibration is really bothering me.  Any Ideas?

[SANDMAN5]

Is this too high an rpm for the "buzz bolt"? I think it is....but my
rememberer tricks me sometimes! If you don't know about the
buzz bolt, maybe someone else can 'splain it....a LOT better
than I could!

[Blackduck]

I take it that the bike has always had this vibration.
Does it change if you apply a little throttle or back off the throttle a little?
Check the Rpm it comes in at and try running in a lower gear at that Rpm and check if it is still there.
Try also running at that speed in the next gear down and see if it shows up.That should give an indication if it is engine related or drive line related/wheel related.
Cam belts can give a vibration/buzz, Carbs with a mixture problem/jets can also give you rough running engine which can show up as a vibration. How many miles do you have up?
Cheers and all the best,
Steve

[dakota450]

I tried going in 4th gear around the same rpm's between 3k & 3500 and seems to not be there or not a noticeable.  I just completely pulled the carbs and cleaned and went through all of them.  I also have an carb sync tool and they are spot on.  Pilots all adjusted properly too.  the bike runs flawlessly just has this darn vibration.  It had a 6 degree trigger wheel which I took out and that smoothed it out some.  The belts looked fine.  45k miles on it.

[Blackduck]

Ok,
Have you tried running in fourth at the same speed?
That should pin point if it is speed or rpm related.
Even having gone through the carbs it is possible that with a drilled exhaust they are leaning out at a steady speed.
Normally I would expect the exhaust to actually improve the mixture as these beasts tend to richen up over 3000 rpm. By chance has the foam pad been removed from the air intake?
Changing the timing and getting a reduction would point more to an engine problem than driveline.
Cheers Steve

[Blackduck]

Should have added, when you say the belts look fine did you check the tension?
You would have had to alter the tension on one to change the timing wheel, did you do both while you were in there?
Steve

[dakota450]

I did try running in 4th at the same speed and it didn't do it.  I thought the tension was set properly on the belt.  I have rounded up a set of stock unmolested pipes to put on it.  After riding my kids with stock pipes, I'm done listening to all that noise.  Its making me wonder if its the pipes.  The engine is not running rough at all and all the plugs read as jetting to be right on.   I had to shim the needles to get it to run right when I first got it.  Once I get the pipes and put them on, maybe that will do it.  I thought it was the rear tire being out of balance but if I am going down hill when it is vibrating and pull in the clutch, it goes away instantly.  It really seems to be pronounced in 5th gear between 3-3500rpms

[R J]

Check that rear tire over good for CUPPING.......

That will cause a vibration.

What pressure are you running in it?
 
I used to run 48 to 50# before I went to the car tire.

[dakota450]

the tire is cupped a little.  40psi but like I said maintaining the speed that it happens at and pulling in the clutch, letting the engine idle while coasting and the vibration stops. 

[R J]

Under power and coasting, the cupped tire does not act the same.

So forget that one.

There is a long bolt, runs all the way across the engine in front.  Tighten it as tight as you can get it.   I used our big heavy air impact to set mine down.   I didn't have the amount of vibration you say you had, that is the reason I suggested the tire.

If the bolt doesn't cure your problem, put 50# of air in the rear tire and go see if it might take some of the vibration away.

[fudgie]

Dyna beads?

[fstsix]

Can you feel it in the handle bars, or is it just the noise that is the concern, i have a little buzz in the handle bars under hard excel in 4th 5th but goes away when just cruising. but i have no vibration on decel.

[R J]

Can you feel it in the handle bars, or is it just the noise that is the concern, i have a little buzz in the handle bars under hard excel in 4th 5th but goes away when just cruising. but i have no vibration on decel.

fstsix, you are feeling that long bolt I was referring to....  Have someone hold the wrench on bolt head on the left side, and either air ratchet or a big breaker bar and a cheater will get it tight.......   It lays in there right about where the horn fastens on a Std or Tourer.

[fstsix]

Can you feel it in the handle bars, or is it just the noise that is the concern, i have a little buzz in the handle bars under hard excel in 4th 5th but goes away when just cruising. but i have no vibration on decel.

fstsix, you are feeling that long bolt I was referring to....  Have someone hold the wrench on bolt head on the left side, and either air ratchet or a big breaker bar and a cheater will get it tight.......   It lays in there right about where the horn fastens on a Std or Tourer.

Ya know ? been about 8 years sense i ran the bike over with a wrench, did years ago, that bar has to be removed to put the huffer on, but thanks gonna check it out.

[Jess from VA]

What about rear wheel bearings?

[Spirited-6]

The minute I pull the clutch in, its stops.  ???

Why would this happen ??? 

[Ricky-D]

I think it's a broken or loose riser bolt.

***

[dakota450]

Risor bolt?  What do you mean and where is it?  Rear wheel bearings are brand new I just put them in.

[R J]

I'd say Ricky-D is referring to the risers the handlebars are mounted on.

Where they bolt to the triple tree.

[valkyriemc]

  I'd say get it up in the air and spin the tire and eyeball it good. Use your hand to feel for high spots, etc. Maybe spin it fast_with the help of another person and see what the bike/wheel /tire does.

[Robert]

I would check the u joint and on the other end check the compression even if you do have all the plugs the same color. My thinking is either a cylinder dropping out or under load the driveline in having problems,my bet would be more on the driveline. Which may include a bad clutch, I cannot answer why it wouldn't do it in other gears until we fix the problem but with a load in cruise it may be just the right combination to cause a bad joint to wobble.

[dakota450]

Its a brand new u-joint.  I replaced it because I thought the one that was in the bike at the time was bad.  The new one made no difference.  Compression is roughly 165 in all cylinders.  I am getting some factory pipes here soon and new dampers for the rear wheel.  When I have the wheel off I am going to take it in and have then check the balance.  I am hoping its either the pipes or the rear wheel out of balance. I am also going to check my cam belts for proper tension.  If nothing stops it then I guess I will just deal with it until something breaks.  I can't think of anything else to check. 

[hubcapsc]

I did try running in 4th at the same speed and it didn't do it...   I thought it was the rear tire being out of balance but if I am going down hill when it is vibrating and pull in the clutch, it goes away instantly.  It really seems to be pronounced in 5th gear between 3-3500rpms

Have you considered steering head or swingarm bearings yet? Seems like you've looked at almost everything...

-Mike

[Robert]

Sorry I didn't see in the first post that you had replaced the u joint. I did notice that you say you had 10k on the rear tire is there any cupping and how much tread does it have? I agree that you are on the right path how about shocks or a suspension issue?