Trident gearbox vibration?

[zzwol]

Hi there, I'm looking for some advice to keep my faithful old 1991 Trident sweet.

I have started to get a rumbling vibration from the engine as it passes through 2500-3000 revs in 2nd gear, which then clears up beyond 3000 revs. The problem seems worse the harder I accelerate. However, there seems to be no vibration at any rev range when in neutral.

I just fixed a minor oil leak from the sprocket cover area, and while I was replacing some seals I noticed there was a small amount of movement in/out on the drive sprocket (Hard to be precise, but perhaps 0.5-1mm). I'm pretty sure there should be NO horizontal movement there. There seems to be no other movement other than in/out.

Is the vibration likely to be caused by a problem with the main bearing on the output shaft of the gearbox? At the moment I'm mentally preparing myself for the worst and to split the crankcases to find out.

I use the bike nearly every day for work, so I'd like get this fixed reasonably quickly (and cheaply, ha ha ha). I don't really want to have to do any unnecessary work (don't we all... ), so when I read in the Haynes manual that it is possible to work on the transmission without removing the cylinder head, I wondered if anyone had any experience of this? Pitfalls etc? Haynes seems unclear and the Triumph service guide says remove cylinder head and everything else.

Help and encouragement please...

[bradtx]

zzwol, No vibration in that rev range while in another gear? I think most transmission servicing can be done with the cylinder head attached.

Brad

[MotT3]

Stiff chain links....maybe time for a new chain & sprockets ???

[zzwol]

Thanks for quick feedback.

I do get the rumbling vibrations at different rev ranges depending in which gear, but the effect is most noticable when pulling away from standstill as I pass through 1st and 2nd gear.

Both sprockets and chain were replaced about 1000 miles ago and have no noticable wear yet. The chain feels to have no tight spots as far as I can tell and is kept well lubed as I use the bike daily.

It was the movement in/out on the drive sprocket that got me worried about the gearbox. Should there be any end movement?

I read that in a motorcycle the most heavily stressed bearing is the output shaft bearing, so is likey to be the first casualty.


PS, thanks MotT3 for enjoyable web site. Love the speed triple and just got to get one of those teflon bushes for my sloppy gearchange pedal.

[bradtx]

zzwol, Try loosening the chain.

Brad

[t552]

Agree.
sounds like chain to me.
Paul.

[zzwol]

Easy to test. I'll slacken chain and see what difference is.

Thanks guys.

[t552]

Give it a good 35-40mm slack. or check the chain when you are sat on the bike to take up the free play.
Bet you find it more 2up under heavy load at low revs.
Just rev the puppy a bit more lol.

[zzwol]

No joy yet. Experimented with various amounts of slack, but vibration still present in same rev range. I'm going to get chain off this weekend and give it a soak.

Still not happy about that in/out movement on engine sprocket though!

[KitNYC]

Is the bolt on the sprocket tight? They have been known to come loose...

Cheers,
-Kit