5th gear vibration

[rzuni]

Lately I have found when I shift to 5th gear at about 70 mph, I have noticed a vibration until I get to about 80 mph. Any ideas what this could be and what I can do to resolve?

Stay in 4th to 80!

[ringadingh]

Try coasting at that speed where it vibrates, either by pulling in the clutch and hitting the kill switch, or just letting off the throttle with the clutch in. This should let you see if its the motor causing it, or the drivetrain. It may be a tire thats starting to cup also. I had a noise once that I couldnt find easily, I took it up to about 70mph and clicked it into neutral, and shut off the ignition, then coasted. With the motor off I found that it was the rear brake making the noise.

Have you ever re-torqued the engine mount bolts? These are the long bolts that cross the entire engine, front & rear, with the rubber mounts on them. To get to the head of the rear one, the left floorboard and sidecover must come off. Mine loostened up by about 5000 miles, and I could feel a lot of extra vibration until I tightened them. I have 30,000 miles now and they've never loostened again.

Another typical cause is a lumpy tire. Made any rubber smoking panic stops lately? Do you cary at least 40 psi in the rear tire?

[ells]

CQ, Do you have the torque spec for those? Should be easy to check the front and then go after the rear if the front was loose.

32 ft-lb & 18 for the little bolts that hold plates to frame. Mine were really loose, I think because the rubber mounts shrink up a lot when first made & then pretty much stabilize. At least they've never loosened up since.

[dank]

How old are your tires? I find that a speed-based vibration is often a tire/wheel is slightly out of balance and is hitting a speed where it has a harmonic resonance. Does it start around 70, build in intensity, and then decrease as you speed goes up? That would match a resonance developing in the tire/wheel. If it is motor-based, then you should experience it at similar rev's in other gears.

...If it is motor-based, then you should experience it at similar rev's in other gears.

This is absolutely true, though the vibration may be stronger or weaker depending on how much load is on the engine at any given RPM. I noticed mine more when going up hill for instance.

[ells]

Have you ever re-torqued the engine mount bolts? These are the long bolts that cross the entire engine, front & rear, with the rubber mounts on them. To get to the head of the rear one, the left floorboard and sidecover must come off. Mine loostened up by about 5000 miles, and I could feel a lot of extra vibration until I tightened them. I have 30,000 miles now and they've never loostened again.

Never noticed too much vibration but, yup, finally got around to checking the front one and took it some to snug up to 32#. Now need to go after the rear - that chrome that has to come off is just a side cover not the side of the engine huh? Looks like maybe the heel shifter needs to come off too? I really should get a service manual.

The side cover is just a decorative cover. No oil will come out.

I managed to get a wrench in there without removing the cover completely from the bike, that is, I unscrewed it but didn't pull off the shifters. I just moved the cover out and down a little & was able to get a wrench on the bolt at that point.