[idk]

I took the cover off and all seemed good to me. The chain tensioner was doing its job and there was no sign of any contact between the chain and case parts. There was no metal or any other junk in the case or oil. I put it back together and the noise is still there.

The noise seems to be coming from the top of the engine. Could it be a valve? Is there something in the hydraulic lifter system that could cause problems, but only at medium to high revs? Is this an interference engine? I shudder to think what may be causing a piston to contact a valve when the engine speed increases.

btw, thanks @Dalmation man.

[GlennF]

I think if it had dropped a valve you would know.

Is the decompressor OK ?

[JVS]

I took the cover off and all seemed good to me. The chain tensioner was doing its job and there was no sign of any contact between the chain and case parts. There was no metal or any other junk in the case or oil. I put it back together and the noise is still there.

The noise seems to be coming from the top of the engine. Could it be a valve? Is there something in the hydraulic lifter system that could cause problems, but only at medium to high revs? Is this an interference engine? I shudder to think what may be causing a piston to contact a valve when the engine speed increases.

btw, thanks @Dalmation man.

If your e-start is okay and the sound does not relate to the sprag, then a few things come to mind.

- Check the front and rear fuel tank mounting bolts for tightness, especially the front one and its associated sleeve/tube/bushing. No. 15/16 in the image below.
- Check the tightness of your mounting bolts for the crash/leg guard and the horn.

When you rev the bike, push the front of the tank downwards / try to keep the weight down and see if it makes any difference to the sound.

[idk]

If your e-start is okay and the sound does not relate to the sprag, then a few things come to mind.

- Check the front and rear fuel tank mounting bolts for tightness, especially the front one and its associated sleeve/tube/bushing. No. 15/16 in the image below.

We have a winner! It was the rear fuel tank mounting bolt.

Many thanks to all. This is what I love about the internet.

[Bilgemaster]

That's superb to hear. An easy fix is a good fix.

[Dalmatian man]

Pleased you got it sorted, one loose bolt made a hell of a noise.