VVVVVVVVVVVVVibration part 5

Willy · 03-03-2001, 09:38 AM

Dealer couldn't fit me in for a balance this A.M., so all I could do was ride today.

Since I have been having this odd vibration from my bike, I decided to run her up a bit today and see if I could make any observations that might point to a culprit.

1.) I let the bike coast at about 120mph and it was dead solid. This would all but discount the balance being off I guess.

2.) If you accelerate constantly up to (approx) top speed it is dead solid.

3.) When you back off the throttle at high speed (120-130), that is where all the fun begins.

It shakes almost like an old BM flat twin I rode once in college. I don't remember this happening on my bike when I had the Cat installed. It is only since installing the (brace-less)Laser Cat Elim that I have notice this stuff.

I said what the hell and just kept on pushing. I hit about 140 a couple of times, nothing happened accept when you close the throttle. What Gives?

Chris Eastburn · 03-04-2001, 07:22 AM

Willy, seems a little strange your experiencing the vibs on deceleration, especially if the problem has developed over time. I'd say run the valve settings, and sync the TB's. I'm constantly checking my TB syncronization, boxers will become buzzy when the TB are slightly out of sync. Also if you have over 6k on your ride swap out the tranny fluid with the BMW synthetic tranny fluid (140/90w), the stuff works great and it also smoothed up the famed 4th gear cyclic vibration on my ride.

You may have a drive line problem, u-joints or bearings. I'd probably check the drive line first. Good luck

EAST

RonC · 03-04-2001, 12:23 PM

Quote:

Originally posted by Willy:
Dealer couldn't fit me in for a balance this A.M., so all I could do was ride today.

Since I have been having this odd vibration from my bike, I decided to run her up a bit today and see if I could make any observations that might point to a culprit.

1.) I let the bike coast at about 120mph and it was dead solid. This would all but discount the balance being off I guess.

2.) If you accelerate constantly up to (approx) top speed it is dead solid.

3.) When you back off the throttle at high speed (120-130), that is where all the fun begins.

It shakes almost like an old BM flat twin I rode once in college. I don't remember this happening on my bike when I had the Cat installed. It is only since installing the (brace-less)Laser Cat Elim that I have notice this stuff.

I said what the hell and just kept on pushing. I hit about 140 a couple of times, nothing happened accept when you close the throttle. What Gives?

Suggestion: when you back off the throttle, weight transfers to the front. Perhaps this is the cause. Cure? Who knows. It is, however, a place to start looking.

Len · 03-05-2001, 02:19 AM

I have a tought. When you are accelerating or even at steady speed then there is a force acting through all the drive line parts. This will have the effect of forcing the parts to keep in contact. When you back off the force is no longer there and so clerances and wear gaps can open up. So movement and vibrations may occur.

DavidSoine · 03-05-2001, 05:27 AM

By any chance do you have a hugger/rear fender or any other unusual parts back there?

This happens _only_ at high speed? What are the exact speeds and gears at which the vibes are noticeable - and where are they strongest?

One thought - You could wire up the exhaust (support it in the middle) to see if it made any difference in the vibes.

Anyway we are now grasping at straws here, it seems. I think what might help sort things out is a detailed, clear and concise description of the history and conditions under which this problem occurred. I know you've posted about this before - but I think it would help to compile the history in one place so our "gurus" can get the whole picture.

Let's figure this out!

Dave

Willy · 03-05-2001, 06:49 PM

Basically, it can be summed up as follows:
1.) Run the bike up to a good clip, say 110-120 range.

2.) Back off the throttle. I am not letting it snap shut or anything, just backing it off.

3.) The higher gear you are in, the more pronounced it is.

4.) The vibration is not the barbuzz variety, but rather a distinct oscillating lower frequency type. It feels like the wheel and tire are out of balance.

I can't figure it out, and, it is bugging me out. Admittedly, it doesn't really happen all the time since you can't run at those speeds for long where I live. Still, knowing that it will start up on you at speed is a pain.

If someone could sort this bike out for me I would be forever greatful. I really like this bike a lot. Its just something that a mechanic isn't going to go out and try.

If I pull in the clutch and let the motor spin down, it all vanishes. It is definately most pronounced the minute you start to back off the gas.

I think I might just get a balance and a new tire. Oh-Well. Maybe it will leave as mysteriously as it arrived.

Anybody want to give it a try, you are more than welcome.

Oh-Yeah, I forgot, I did try to safety wire the pipe with some hose clamps. No Dice.

[This message has been edited by Willy (edited 03-05-2001).]

alq2 · 03-05-2001, 07:04 PM

Willy,
You initially mentioned vibration, then later oscillation. Could you possibly be describing the front end shaking back and forth due to a front tire that is wearing unevenly? I've had bikes that would do that on deceleration, particularly when I would let go of the handle bars. The problem would go away once a new tire was put on the bike.

lennie · 03-05-2001, 10:57 PM

Just a thought.

After one of the guys nearly lost his rear wheel I thought I would check mine. There was play and after checking the bolts were tight I found the hub pivot bearings on the rear of the swingarm to be shot.

I sometimes get an oscillation at speed but not the throttle shutdown problem. I suggest having a good look around in this area and if any doubt replacing the bearings. Not sure if this is the problem, but have a good look anyway.

Grab the wheel at the rearmost and try moving it sideways,

Regards,

------------------
LENNIE

[This message has been edited by lennie (edited 03-05-2001).]

Willy · 03-06-2001, 04:25 AM

Anything is possible, however, front tire looks good. It is a pilot sport with about 2000 miles on it. The rear looks about 1/2 way gone. As ususal, the front appears to have minimal wear. I know that this vibration is coming from the rear of the bike. If it isn't, I'll be damned.

It is not the hand numbing buzz that is endemic to this bike. It is almost the same type of feeling I would feel through my Sportsers bars under acceleration. Just a pronounced low frequency vibration.

I have had the swingarm pivot bearings tightened. They were loose, but now feel good. The hub bearings seem to rotate freely, and exhibit minimal play.

If you grasp the tire at 9:00 and 3:00 you can push / pull both hands in and out in the same direction to feel the swingarm bearings are good.

Pushing and pulling in the opposite direction exhibits almost imperceptible play in the hub bearing.

I live in Northern New Jersey. If there is a good mechanic near me, let me know. I don't care about warranty work. If someone knows what they are doing, I will gladly pay them. I've already had enough "expert" warranty work.