Valve Stem Seals

[johnr]

has it got the stock airbox on it? is the breather routed into the airbox? if so, have you checked in the airbox for oil.

[johnr]

everything would suggest its burning oil, but so soon after a rebuild it seems unlikely. but, that oils going somewhere, so with the occasional puffs of smoke, it can only be bores or valve seals. however, the baffle issue could have had a bearing, but it depends on what restriction it made in reality. i suppose refitting it where it should go and making it unmovable and then running it to see what happens is the next order of the day. did you get the bores done or honed when it was built?

[DEANOTEK]

Id check the valve stem seals. If you replaced them did you check their 'tightness' on the valves. Ive had some before where they were way too slack on the valve. They would have definetly sucked oil past if fitted. I use viton ones now with no issues, but genuine ones should be good too...
Make sure the seals 'pop on' to the stems correctly, plenty of oil on to lube the valve stem tops, its easy to fuck up here, because the crappy wire circlips on the seals can become displaced sometimes. Easy job.. but easily got wrong too, if not enough attention is paid to making sure those pesky wire circlips don't move.. The seals can lift off the valve stems & let oil down.
A good honing job too is vital on the bores too..

[sparki]

like we chatted about, unless something happened when you changed the seals to the oem ones i cant see how the others, and the new ones all had an issue... as roger put the top end together im sure he would have noticed if one of the bores was scored or damaged, especially after doing work on the block.

one thing id ask him though... as the other muppet put the motor together first... was, did roger put the rings on the pistons? if he didn't touch them or if he simply removed the pistons when he did the work and simply popped the block back on without checking i really think there's a chance that the previous twat stuck a scaper ring on upside down... as you say its only a single pot smoking, #2, and the compression is down on that one, i think this is a real possibility.

check with him if he remember what, if anything, he did with the rings and go from there... i cant see, given what you've already looked at and changed, how it can be much else...

[stockcar]

duff oil scraper ring wouldn't affect the compression................

could be worn valve guides??

[fossie]

Seems like an honest answer to me. I thought the rings were new, but used rings are a different thing, which is why we decided to fit new rings to this 650 which seemed fine.

Remember also that some engines are disingenuous to use oil from the start until the rings shape to the bores.
Volvo trucks , Volkswagen to name 2 ...new bores and shaped rings will be just such.
Live with it for 12 months to see how it goes . Stop tinkering and get riding...........( and carry a breakdown card!)

[stockcar]

Hi Stockcar, cheers for the input, not doubting your advice as I really don't have much of a clue about engines but does the guide not sit under the seal so if it is worn would a new seal still not cover it?

If the guide itself is worn it will goose the new seal in short order as it allows the valve stem to move around

[johnr]

yeah, a worn guide will allow slight lateral movement of the valve, possibly enough to affect both the seal and the compression as it wont be seating right every tme the valve slams shut. however, i find it pretty implausible that roger upperton wouldnt have mentioned this if he built it up.