Unfortunately it looks like time to do the full top end tear down on my 1972 R75/5 (valves and guides were done 2 years ago - should have bit the bullet - and the wallet - and done the lot at the same time). Motor is using too much oil and blowing blue smoke under acceleration. Full service has been done but before I lash out the big dollars I'll do a compression test and a leak down test. I'm also going to attach an oil pressure guage and check that the bottom end bearings are ok (shouldn't be the reason for the oil problem but should indicate if I have to overhaul the bottom end as well). So I'm looking for some remote diagnostics if anyone is able to help: motor still seems to have plenty of power blue smoke comes from the right exhaust when the engine is revved it gets less when the engine is hot - after an hour ride it disappears previous work includes new valves, guides, seats, valve springs, top end gaskets, push rod boots I've got no idea how many miles the bike has done - original speedo has long since gone full service was recently done carbs have recently been rebuilt with new gaskets, jets, etc (less than 500miles ago) right plug has oily residue on it left plug looks like it is running a bit rich (sooty black residue on it). So part one of my question is this: Are there other things I should be checking for before I spend the big bucks on boring out the cylinders and replacing pistons? I've heard that the crankcase breather can spit oil into the right carb if faulty? Part two of my question is: what oil pressure should I be looking for on this bike? Last part of my question is: If I do have to rebore and replace cylinders I'll be doing most of the work myself (except for cylinder measuring and boring) and am just getting my prices together. I read this comment on the Boxerworks forum: So I look on the Motobins site and see that a pair of r80/7 pistons comes out at $254 AUD compared to $390 AUD for oversize R75/5 pistons. Both prices include rings, gudgeons and circlips. Has anyone had any experience of doing this? If I go down this path am I going to find myself with some very thin walled cylinders? Has anyone got any better ideas? I've looked at several sites and the Motobin price is about the cheapest I can find for R75/5 and R80/7 pistons. Anyone have any leads to a cheaper source? Alternatively anyone got a better idea? I'm based in Australia. Ive looked at the very nice pistons on the motor-israelen site but they're even more expensive than the Motobins ones. Any response gratefully received.