Vibration in 1200 Sport

[Bisbonian]

I have a cyclical vibration that I get at lower speeds on my 1200 Sport.

I can feel a rumble in the pegs that sort of cycles on and off in a consistent manner.

It doesn't seem to matter what gear I'm in.

By lower speeds I'm talking about around 40 and below; once I get above that I don't feel it but that doesn't mean it goes away, it could just be that the cyclical nature of the vibes start to blend at higher speeds and get lost in the background.

Sometimes this is quite pronounced and bothersome.

I have about 15000 miles on the bike but it's been doing this for probably the last 7000 or so, at least that I've noticed.

I'm good at ignoring it when I get up into the speeds where I don't feel it anymore.

Could this be normal? What sort of testing, aside from disassembly of the entire drivetrain, can I perform to try to narrow down the problem?

If it's a real issue it would have to be in the transmission, driveshaft or CARC; that doesn't narrow it down to anything inexpensive at first glance.

 

[draidt]

Check the exhaust system from both header pipes all the way back for loose bolts, leaks/cracks at the crossover pipe, to part of the exhaust touching the frame somewhere. could also be a badly unbalanced throttle body connecting rod adjustment.

 

[Bisbonian]

Check the exhaust system from both header pipes all the way back for loose bolts, leaks/cracks at the crossover pipe, to part of the exhaust touching the frame somewhere. could also be a badly unbalanced throttle body connecting rod adjustment.

I'll check the exhaust.

If the throttle body connecting adjustment was out wouldn't that cause a running issue?

I should have added that the engine runs perfectly at all speeds.

 

[Penis Rotor]

Cyclic vibration through the footpegs on a Loop or Tonti was usually the sign of a UJ going tits. So far I haven't heard of a CARC driveshaft needing replacement though.

It might be worth just peeling the boot forward off the front of the swingarm and running your finger around inside by the front of the shaft just to make sure there is no metalic dust but it would probably prove un-neccessary. Rear coupling is easily inspected by just dropping the CARC off the rear of the swingarm.

I'd double chack the tune and the bolts that hold the engine mounting plates to the frame downtubes at the front.

Pete

 

[Bisbonian]

Cyclic vibration through the footpegs on a Loop or Tonti was usually the sign of a UJ going tits. So far I haven't heard of a CARC driveshaft needing replacement though.

It might be worth just peeling the boot forward off the front of the swingarm and running your finger around inside by the front of the shaft just to make sure there is no metalic dust but it would probably prove un-neccessary. Rear coupling is easily inspected by just dropping the CARC off the rear of the swingarm.

I'd double chack the tune and the bolts that hold the engine mounting plates to the frame downtubes at the front.

Pete

I had the swingarm and CARC off a few months ago to replace the boot between the transmission and swingarm. There was a bit of dirt and greasy stuff on the inside of the swingarm but I didn't see any sort of metallic dust. The problem had been going on before this operation so I was looking for anything obvious at the time.

Sounds like it's time for a good going over for the whole bike as this could likely not be driveline related at all.

 

[Bisbonian]

Well I tightened up everything, not that any bolts were loose and checked the exhaust for any rubbing or touching. Just to be safe I remove the center stand as I could see how that could transfer a vibration as well.

Nothing has changed.

However I have narrowed this down and the vibration only happens in third gear. Unfortunately third is the gear I use most of the time when in town.

Since I'm in no hurry to even consider removing the transmission and see what's going on inside it I think I'm going to ignore this for the time being and consider it a "feature". It is possible that this is completely normal and there is some sort of harmonic that sets up in third gear.

 

[draidt]

Well I tightened up everything, not that any bolts were loose and checked the exhaust for any rubbing or touching. Just to be safe I remove the center stand as I could see how that could transfer a vibration as well.

Nothing has changed.

However I have narrowed this down and the vibration only happens in third gear. Unfortunately third is the gear I use most of the time when in town.

Since I'm in no hurry to even consider removing the transmission and see what's going on inside it I think I'm going to ignore this for the time being and consider it a "feature". It is possible that this is completely normal and there is some sort of harmonic that sets up in third gear.

OK you have narrowed down a bit now at what RPM range does the vibration occur ? Does it disappear at higher RPM's with some more throttle only to reappear when dropping it down to a lower RPM ?

High RPM (3000-4000) Unbalanced TB's is still an option, Engine performance will not be affected, but vibration will be.

 

[Bisbonian]

OK you have narrowed down a bit now at what RPM range does the vibration occur ? Does it disappear at higher RPM's with some more throttle only to reappear when dropping it down to a lower RPM ?

High RPM (3000-4000) Unbalanced TB's is still an option, Engine performance will not be affected, but vibration will be.

Mostly around 3000 rpm.

I'll throw the carb stix on it and see what shows up.