Anyone know of a 20 thou over high comp (8.1 or 8.1/2 comp piston new or secondhand with the long rod specs? Or an overbore 400cc piston from some other make that doesn't require a huge barrel spacer? Ian? Bought a B40 piston but the overbore would make the barrel too thin and the deck height is way out.Deck height is roughly 30mm.Are all B31 and B32 pistons longrod? Have an M21 60 thou over new and new 40 thou over M20 to do a deal. Also the B40 new and standard size. All with rings and gudgeon pins.The catch is I'm in Oz.The pistons are genuine BSA. Douglas.

Hi Douglas..All iron 350 motors are 'long rod'...I may have a suitable piston I'll take a look today and post here later....Ian

email (option): ian@wright52.plus.com

Hi Douglas...I have a NOS Heplex +.030" for a B32..not sure what the compression ratio will be with this one,,It is flat topped but approx. 1/4" to 5/16" higher than the standard B31 piston, so 7 or 8 to one I would imagine.
Unfortunately the two compression rings are missing so I will have to get some more original ones to make it complete.
Let me know if you are interested and I'll get in touch with some of the piston ring dealers to find some...Ian

email (option): ian@wright52.plus.com

I'm confused about the flat top part and the high comp part Ian? The original in front of me is flat topped.Does it taper in on the sides to clear the edge of combustion chamber? Do you take pictures?

Hi Douglas...Yes, the edge is tapered...It's the same pattern as the high comp. M33 piston for the 500...Ian

email (option): ian@wright52.plus.com