Driveline Vibration:

[djpttrsn]

My R90S has an intermittant, fairly high frequency, vibration that comes in at various speeds from 30 to 70 MPH. It starts like it is being switched on. It's not there and then, without warning, it is there. It goes away when I pull the clutch in and let the RPM's drop. I let the clutch out and the bike is vibration free - until it isn't. I surmise that it may be coming from the clutch, pressure plate, flywheel, U-joint - again, somwhere in the driveline. This, of course, is not R90S specific however, I thought I'd start here and see if anyone has experianced this and what the cure might be.

I have been riding the bike for several years and the problem has been there but has not gotten worse. The vibration is somewhat disconcerting and I plan to investigate over this Winter.

Key to the problem is that the vibration is intermittant and does go away when the clutch is pulled in.

Any suggestions or ideas would be much appreciated.

[schrader7032]

Welcome to the forum! I'd start with the four bolts that secure the driveshaft to the output flange of the transmission. You try to feel the bolts through the rubber boot, but I think you're going to have to loosen the clamp and move the boot back to visually inspect and see if will tighten with a wrench.

[djpttrsn]

Thanks for the reply. I will go after the four bolts and let you know what I find. I would like this to be a quick fix but have a strong feeling that I will be diving deep into the driveline before it's all over.

Dale

[srankin]

How many miles on the bike? What work has been done in the past to the clutch system? St.

[djpttrsn]

The bike has about 4200 miles on it since completion of it's restoration. Before restoration the bike had sat out in the Oklahoma weather for about 15 years. The engine was locked up and it was in a sad state of disrepair. The engine has been rebuilt. The transmission seemed to be okay and was not disassembled or rebuilt. The driveshaft was not removed from the swingarm and the U-joint was not replaced. Everything clutch related was replaced with new.

As mentioned, the vibration will go away if I pull in the clutch and let the RPM's drop, everytime. The vibration will come back after 7-10 minutes riding at various speed and RPM's, everytime.

[srankin]

Are you the original owner? Do you have any idea as to how the bike was ridden or maintained before it was stored?

Did you do the restoration or did you have it done by someone else? When you/they pulled the fluids out was there any sign of water in the transmission gear oil? If there was it would have been milky looking. If it did have water in it I would safely assume a bearing is shot. Sadly even if the gear oil was clear, it could still have a bad bearing.

The same goes for the engine bearings. Did the crankshaft come out to allow a proper inspection of said bearings?

Yeah, I know I am being negative, if you are not the original owner who is to say he didn't ride the heck out of it and never change the oil? Certainly sitting out in OK weather doesn't help. I am assuming you get rain and snow (my sister lives in Atoka) so moisture can be a killer. As for moisture getting into the transmission most of the time that is because the speedometer cable plug breaks down and rain or carwash spray can enter.

Not to knock you or the shop that did the work, perhaps a look over at the work done during restoration may give a clue. I will say I have made mistakes in repairs and when I find something I rebuilt is not as it should be, I recheck my work.

I am sorry to be a bum, I really would like to point out some smoking gun causing the problem that is easy to fix but I personally don't think there is an easy fix.

The problem could be a consumable item such as the clutch disk. I see you installed new items but sometimes even new items have issues, rare but not entirely unheard of.

Winter is coming so perhaps you will have time to look things over and find a solution, Good luck. St.

[cbclemmens]

The fact that the vibrations go away when you put in the clutch suggests the vibrations are on the engine side. Even so, I would check the final drive. I assume you changed the gear lube in the final drive and gear box. You can spot check the play in the final drive by removing the rear wheel and try to turn the hub while holding the universal joint. It shouldn't move more than a millimeter.

Craig