Hi all, I am a newbe on this site and looking for some advice, I have a 1981 XR3 which is running rough, had a carb guy service the Weber 32/34 which is fitted to this car but still running rough. Runs good on high revs but not on low revs. Got a compression tester to check and did 2 tests, first test , removed plug on 1st cycl and tested leaving in plugs 2,3,and 4, removed plug no 2 and tested and did the same for no. 3 and 4. My second test was with all plugs removed. these were my results.

1st test. cycl 1, 150psi 2nd test cycl 1, 150psi

no 2 175 no 2, 110

no 3 140 no 3 105

no 4 145 no 4 125

If anyone on here can point me in the right direction before I tear everything apart I would be very gratefull.

Hi welcome

Hi Vincent welcome to the forum 😁

Hi, It's probably valve seat regression buddy, losing the compression

Could just be a weak valve spring or a sticking follower, but I doubt it.

But whichever way, she's due a rebuild now and that's what I'd recommend, with a full refurb of the head

Or drop an ST170 in it😜