Hitchcocks Forum

So what is the actual recommended ring gap please anyone? 1990 350 Bullet. bored to +20 and new piston ready to go in. Rings come with piston and give me 15 thou gap. On the piston box it said set gap to 12 to 15 thou. In the workshop manual it lists 15 to 20. This is the same scenario with my 250 Crusader. want to fit new rings to honed bore in that engine.
Also, is it permissible to take new ring set over size and file down to fit. ; ie., use +30 in the + 20 bore, filed to give selected gap?

Hi, go with 12 thou . I have filed oversize rings to fit without any running problems although not technically correct. Vince

Thanks Vince, can do that.

I once did this (o/s rings filed to fit) on a Vespa scooter in my yoof. Never ran properly again; damaged bore, poor compression.
If I were you, I wouldn’t do it...