speed fight 2 defying the odds ??

Right so I put a new top end on one of my speed fights. Oil pump was fine, no bubbles in the line. So I did the heat cycles to break it in, a couple minutes ride and let it cool down ect ect.
Then last night I was riding to the local village, down a slight hill. I hit 40-45 and the back wheel skidded up. I pulled over, kicked it over and off I went. Today I checked the compression and it was 75psi. And it started easier now, cold than it ever has. Revs up fine, exhaust feels like it's chucking out a fair compression.
Has this bike defied the odds ? or you think I have a dodgy compression tester and it's not that low compression ? Because I have had enough bikes with that compression before and they were tough to start..

Any help will be helpfull

 

Heat seizure.
Most kits need about 300 miles to run in properly at speeds no more than 30mph (50kmph).
If the rear wheel is locking up, i'd be checking the gearbox for oil, then stripping it out to check for failures.
You're right about the compression, it shouldn't start on that psi, but check it again to be sure, or try another tester to copy the results.