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[Dave the Bass]

Hello,

I'm slowly rebuilding my beluvved 1991 500cc Bullet. I have a replacement Alloy Barrel, new piston and new rings.

Can I just check that the Piston Ring end-gaps measured in the bore are correct please? I've got...

Top ring (Comression-Tapered on both outer edges) = .021"
Middle ring (Scraper Plain) = .017"
Bottom ring (double Oil control) = .016"

They were too tight when supplied new so I've had to very very carefully file them to get those gaps. I've seen reference to a tolerance of .015-.020" often quoted at various sites on the internet. I though I'd best check here 1st before I continue with the rebuild.

Ta,

Dave.

[ChrisD]

Hi Dave the Bass. The only information I have is from my Accralite piston in my 1996 535cc. In an alloy barrel, you MUST get the correct bore diameter otherwise the piston will seize. Needs a total bore clearance of 6.0thou for that piston in alloy barrel. I had my first accralite piston installed with 5thou clearance and it kept seizing.

The ring gaps are given by Accralite as follows: top=10-16thou, middle =12-18thou and oil ring=8-16thou. And these are NOT measured at the top of the barrel. Place the ring in the barrel and slide it down a few centimeters using the piston to ensure it is at right angles to the bore. Note these may be different for another type of piston

Shouldn’t the piston supplier have given you the correct info?

I hope you are not putting one of the "grenade" OEM pistons back in - they will self-destruct.

Cheers, ChrisD

[Tim NZ]

The 'Grenades' are serviceable so long as you dont thrash the bike AND replace them every 6000miles...

[Dave the Bass]

Thanks for the replies, I'll check to see if I have a grenade firstly