Low RPM Vibration: valve/cam vs piston/cylinder clearance

[Guest]

My bike has a lot of low RPM vibration, most of which smooths out at higher revs. The carbs were rebuilt, valve buckets adjusted, and carbs properly synchronized.

I'm in the middle of a top-end refresh:

• I checked the valve clearances and found that #1 exhaust had less clearance than my smallest shim, all the rest were between .06-.08mm. My hunch is that we mis-adjusted #1 exhaust, but I guess it's possible it wore down that much?
• I measured the piston:cylinder clearance per the manual. It's exactly at the service limit for clearance, and the pistons are exactly at the service limit for 'diameter'. Of course, this is before the cylinders get honed

I'm trying to decide if I should get a new set of pistons or not. It's hard to say if the vibration is caused by the piston wear or the mal-adjusted valve, but I recently read a review about another Suzuki bike which suffers from low RPM vibration due to the pistons 'leaning'. Of course I don't want to open the engine again, so I'm wondering if I should replace the pistons or not. I know it will be 'fine' if I leave them alone, but the vibration is annoying to me, and certainly won't help if I decide to sell the bike.

(Edit: Of course, this thinking was when there was a NOS piston set on Ebay for $100, which I should have bought )

What do you think?

[hillsy]

Have you checked all the engine mounts are torqued correctly?

[Joe Garfield]

Have you checked all the engine mounts are torqued correctly?

Yes, a few times.