2500 TC Manual engine vibration

[Bikerboy_nz]

Hi all, I have a 77 Tc2500 manual (75Kms) that has an annoying non-harmonic engine vibration no matter the revs that 'feels like' a flywheel/engine inbalance. It is quite obvious even when the clutch is engaged (so certainly engine issues and not drive train problem which I had actually hoped for!). It was especially bad and in replacing gearbox and engine mounts improved things- but still remains an ongoing problem

I had thought this might be another problem like compression fault (pistons/rings/valves etc) but the compression is excellent 170+ psi on all and little or no variation between cylinders. The engine goes well otherwise, is quiet (not rattly eg, bottom/big/small end) and runs normal plugs colours/clearances, etc. Has all new HT/LT electrics, also running luminition  so does not appear at all ignition related (also as I had hoped)

The Triumph specialist I went to said that there was apparently a problem with some engines that were like this 'from new' and he said their experience of taken engines apart and having them properly balanced really did not seem to make any appreciable difference - strange???

Any thoughts/ideas or suggestions much appreciated?

Jason

[RobPearce]

If you think it feels like a balance problem then I'd have expected it to be a balance problem. I'm a little surprised at your local specialist's comments.

These engines have a harmonic damper behind the front pulley, which is known to fail, so that's worth a check.

[Pete Lewis]

plus have to run it with the viscous fan removed ???

Pete