Hi, I have a 1995 GL1500 and it has a slight light rattle at idle when hot. It has covered 55000 mls, i have checked valve timing and carb balance all seems good. bike runs perfect except for noise, any ideas ?

Probably the vacumn slides are hanging up, Not because they are stuck, But because the idle screw is set too high to get to idle. The idle will usually hang up at 3,000 rpms. Set the idle mixtures at 1 1/4 turns out & make sure the throttle cable has play. Now back the carb idle down till it just idles about 1,100 rpms. with choke off. If the carb sync is way off, I will hang up on 1 carb when hot. You need a vacumn guage set to make sure they are balanced. To check the spark advance (which I doubt), Put a timing light on the LH plug wire & shine it at the timing marks behaind the LH cover on motor at botton covering the generator. It should be on the F marks at idle & at the unmarked line aprox 1 " over which is full advanced when reved up to 1/2 throttle. But yes a air leak at the intake manifold could cause it to rev, But will be a very erratic idle at 1,100 rpms. If the idle circuits are working correctly, You should be able to kill each cylinder with turning in the mixture screws one at a time. That checks the idle jet circuits.

I think you had better have a local shop inspect this for a failed engine connecting rod.

The rattling is a worn-out timing chain (rattling should be louder at one end of the engine). Get it changed now - they will eventually break, closely followed by your bank balance!

check again for a vaccum leak between the carbs & engine (new o-rings in those inlet rubbers???), then re-sync carbs.

check to see if there is any carbon on the throttle body where the butterfly contacts it. also clean the " business end" of the idle air valve to make sure it's not being held open slightly.