tinny rattle.

[Muttleyoo7]

I'm going to have a look at the weekend and will let you all know what I find.

[Nigel. S]

I have what sounds like the exact same thing. It's driving me nuts. Runs fine but throttle off to change gear (up or down) and you hear it. If you slow the engine down with rear brake rather than throttle completely off you don't hear it. Mine also nipped and I cleaned up piston and cylinder and put new rings in. I initially thought I'd put the head cowling on slightly differently to how it was, it also has no fibre pads which I might have to add just to rule it out. If I tap around the underside of cowling with my finger there is a point where it taps against the cylinder (or something) and makes a very similar if not exact same sound.
I have to admit I didn't check piston/bore clearance. I now wonder if the nip up has inflicted further damage to one end or other of rod. But I also wonder - did it do it before nip up?! Jeez I can't remember .
Also noticed when I was on the way to Shipston, (after new rings etc) and almost there, that I could swear I could hear a deep drone/hum when I was pushing the poor thing as much as I dare. Which I instantly thought - bearing. I know you get tuned in to every little squeak and fart especially if on a long distance run and get a bit paranoid, but it was definately there. I pushed on in the mindset that if it's something that's gonna let go it would have done it by now And it got me home again.

I wondered about pinking too, but need to swat up a bit on that, causes/cures etc. Nothing has changed though with engine setup (standard LI150) so not sure about pinking.

I will fumble on until I find it either myself or by checking back on your progress
I'm feeling your pain.

[sunrisemac]

I have what sounds like the exact same thing. It's driving me nuts. Runs fine but throttle off to change gear (up or down) and you hear it. If you slow the engine down with rear brake rather than throttle completely off you don't hear it. Mine also nipped and I cleaned up piston and cylinder and put new rings in. I initially thought I'd put the head cowling on slightly differently to how it was, it also has no fibre pads which I might have to add just to rule it out. If I tap around the underside of cowling with my finger there is a point where it taps against the cylinder (or something) and makes a very similar if not exact same sound.
I have to admit I didn't check piston/bore clearance. I now wonder if the nip up has inflicted further damage to one end or other of rod. But I also wonder - did it do it before nip up?! Jeez I can't remember .
Also noticed when I was on the way to Shipston, (after new rings etc) and almost there, that I could swear I could hear a deep drone/hum when I was pushing the poor thing as much as I dare. Which I instantly thought - bearing. I know you get tuned in to every little squeak and fart especially if on a long distance run and get a bit paranoid, but it was definately there. I pushed on in the mindset that if it's something that's gonna let go it would have done it by now And it got me home again.

I wondered about pinking too, but need to swat up a bit on that, causes/cures etc. Nothing has changed though with engine setup (standard LI150) so not sure about pinking.

I will fumble on until I find it either myself or by checking back on your progress
I'm feeling your pain.

PRE-IGNITION
The definition of pre-ignition is the ignition of the fuel/air charge prior to the spark plug firing. Pre-ignition caused by some other ignition source such as an overheated spark plug tip, carbon deposits in the combustion chamber and, rarely, a burned exhaust valve; all act as a glow plug to ignite the charge.

DETONATION
Unburned end gas, under increasing pressure and heat (from the normal progressive burning process and hot combustion chamber metals) spontaneously combusts, ignited solely by the intense heat and pressure. The remaining fuel in the end gas simply lacks sufficient octane rating to withstand this combination of heat and pressure.

[Muttleyoo7]

Fixed with a Dremel! It would appear that when the down pipe and the head cowl warmed up they expanded enough to touch and vibrate. It didn't do it when I rebuilt the engine, but it was a new head cowl and I guess it had settled and moved slightly in use. Anyway I've opened up the cowl where it fits around the down pipe and the noise has gone.

May I also say a big thank you to everyone that offered advice.

[steveg]

always nice to know the outcome of these probs

[Nigel. S]

Glad you found it. Will check that on mine too

[Muttleyoo7]

Glad you found it. Will check that on mine too

Good luck!