Piston Ring gap

[chris2470]

I hope somebody can give me some input on the following.
I've just put together my new top end, its a cleaned up and tuned 225 Ali barrel with a steel liner. When I fitted the rings into the barrel straight out of the box the gap was 0.5mm. I have seen the figure of 0.05% of the bore as a clearance figure which would give 0.35mm.
So I have 3 main questions:
Will 0.5mm be OK to run with?
After I have run it in for 500 miles should I check this clearance again and if needed fit some more rings and this time try and gap them to 0.35mm.
If I fit some new rings at this stage how many miles would I need to run them in for.

[byron]

0.05% of 70mm is 0.035mm, which is probably better than 0.5mm...
I'm about to check the rings on my Mugello, so would be interested to know if 0.05% of bore is a good figure to go with.

[byron]

anyone ?
planning to check the top end this weekend

[corrado]

See page 66 of Sticky's book.

[chris2470]

Hi Byron
I put mine all back together yesterday and used a figure I got form a well known 2 Stroke tuning book. This gave the figure of 0.1 - 0.12 mm per Inch of bore.
Hence 70.2mm bore = 2.76 inches x 0.1mm give me 0.276mm or 11 thou in old money.
Pretty much spot on what Stickys advises.

I hope this helps.

[byron]

yep thanks, it does.
and cheers corrado, I should've looked through the book