I finally got the T140 running, but with a top speed of only 80 mph, so the first step was a compression check. The drive side cylinder was about 110 psi with 60 psi on the timing side. Next a quick check with a few cc's of oil in the TS cylinder gave 100 psi indicating a ring problem. After removing the cylinder barrel the only difference I noticed was a scuff mark on the TS piston,
At this point I will do a cylinder hone with new rings, but I have some concern about this mark.
Does this mark tell me anything about why the compression was low?
The mark feels smooth and both cylinders look good, so is it safe to use the same pistons?
Also what exhaust are you using...…...I can remember having a Trident with pattern Campbells mufflers that wouldn't do over 80....replaced with more open sports type mufflers and the same bike did over 110 mph easily [maybe could have got more, but didn't try]. Plus just felt more powerful all round.
If your bores measure up OK, using that piston again [with new rings] would be fine.
Agreed re trying without silencers. I had Campbells megaphone shaped silencers on a T140 I bought once. Utterly gutless and would not go over 80. I took them off and it was as if it was supercharged, in comparison.
If anything other than a blank space is visible here, something's wrong.
Flip the head over and pour the CHamber full of lacquer thinner and see if it ends up in the ports, If so you also have a valve issue! I have seen lots that the piston scuffed like that and the comp wasnt much if any lower, I bet you have a valve issue. Prob some trash between the valve and seat. Good luck