DaveK said:Is the stock domed pistons lower compression then the combat pistons? (or do "combat pistons" even exist)?
Anyone know?
Seeley920 said:It sounds like you mat have powermax pistons (which are higher compression) as they had a slight dome on them. Other (standard) commando pistons all had the same deck height as far as I'm aware
Ron L said:Combat motors had the same piston design as all other 750 Commandos. I believe the term "Combat pistons" originated with the Hepolite pistons that had deeper valve reliefs and later with no slit behind the oil ring. These were all flat-top. Compression increase was from a milled head and is readily visible when compared to an earlier head.
As to P11's and G15's using PowerMax dome pistons, the four P11 motors I have all had flat top Hepolites with the one-piece oil ring and no valve reliefs, just like the Atlas. I'm sure that adding domed pistons was common hop-up at the time.
Weren't domed PowerMax pistons part of the Dunstall kit for 750's?
RoadScholar said:I meant to post this in a new thread, but this is a good place.
I am anxious to see what bearings I find in the lower end of this engine, which appears to be unmolested.
RS
Ron, I don't know how many bikes came with powermax pistons, but I know my 68 N15 had them when I bought it new.
MarshalNorton said:A compression gauge should tell you what its pushing.