I decided to rebuild the top end of my M20 because the crankcase pressure was too high and the breather turned out to be OK.So I expected a rebore or worn piston rings.
When I took the cylinder off I found a ridge on one end and a smooth bore on the other side. I had to realign the conrod and fit new rings as the gap was not in thous but milimeters. (afterwards I found that at the last rebore +.020 rings were fitted on a +.040 oversize piston). After lapping in the valves I rebuilt te engine looking very pleased with myself after honing the bore and fitting new rings. I was cleaning up when I noticed 2 circlips lying around. I couldn't help uttering some nasty words and taking the top end off again to refit the gudgeon pin clips and rebuilding the top end again. Although I had worked so methodically I had completely overlooked the circlips lying on the paper I used to spread out all the nuts and bolts taken off the bike at the disassembly. It ran perfect afterwards so it turned out OK but I couldn't take the bike out for a ride because it was too late and I don not trust Joseph Lucas too much.
Regards,
Leon
email (option): leonhop3@planet.nl
i rebuilt a b31 engine which is back it the frame something is niggling me have i put the oil flinger on the crank the right way round i put it the same way round as the one that was in there but it was the bearing near the flinger that seized 
Easily done Leon..it was fortunate you didn't start the engine before realising the omission!
I once 'forgot' to put the pushrods in a B50MX...I realised when I tried to complete the last job of setting the tappets
...Unfortunately the engine has to come out of the frame on that model to get the head off..DOH!!...Ian
email (option): ian@wright52.plus.com
What's with all this "I once" did this or that? I screw up "every" time I have a spanner in my mit!! Got you all outclassed!!
Cheers
Pete
email (option): petercomley@web.de