Hitchcocks Forum

Just checking through everything for the top end before assembley. I have a new unused std bore barrel and a new split skirt piston without rings. The piston "parachutes" nicely down the bore and I can just get a 3 thou' feeler guage between the bore and the skirt, - So I'm assuming that is somewhere between slightly tight and ok.
When I check the rings (marked std) they have little or no end gap when fitted square into the bore. 2x compression rings = 2 - 3 thou', Oil ring = 0 thou.
Does anyone have any figures for the endgap for the rings?
Cheers,
Zippy

Hi Zippy, I've had a look in the old manual (500cc) and it seems to correspond with Mr Snidel, shown below..

I can find no actual clearance figure for the piston but i think thats close, ie the forged piston needs greater clearance at about 6.5 thou..

The manual gives the maximum ring gap as 0.039"

Thanks Gwilly for the quick reply - I thought the "3 thou' for every inch" rule was a bit mean, giving a gap of only around 8 thou' I haven't had to gap rings since a Honda in 1984, when they couldn't supply rings for 1st oversize.They put them on backorder. I had to get the "next rings up" and gap them myself. It all ended badly as it kept breaking top rings. Closer examination showed that the barrel was bored like a spiral staircase. It's 2014 now , and the rings are still on backorder... :/

Well, all has gone together suprisingly easily, crank is in , Rings ground to 15 thou', barrel is on. I didn't even need the ring compressor.A leak test on the head now - then that can go on .