This is possibly a stupid question but here goes, I don’t mind looking stupid...
A few people have mentioned a tight engine could be contributing to the problem which seems logical.....but how tight is tight????
I’m turning the engine over using a ratchet about 8” long on the end of the engine sprocket (I have a nut securing the sprocket on the cush drive not C-Spanner thing), there’s no primary chain or rocker box fitted and the plugs are out. All the timing gears, oil pump, mag and dynamo are fitted. The effort required isn’t huge but it doesn’t exactly spin freely. I certainly can’t turn it by hand on the cush drive.
It’s probably about 4 years since all the bottom end was rebuild by SRM, but I reckon I’ll have only done something like 1000 to 1500 miles in that time.