Topic: Burning oil on cold start

[OakBehringer]

Winter is here and, since I can't ride, it's time to do some more serious engine-off-bike work. On a cold start, I get anywhere from a little to a lot of blue smoke coming out of the pipes. Once it warms up, no more blue smoke. I'm thinking this is probably rings not sealing until it warms up and they expand?

Thanks for the advice,
Adam

[Johnie]

Could be the valve seals leaking down while the bike sits.  Then when you start it up you are burning the oil that seeped past the seals and into the cylinder.  Once you get that burned off it is OK until it sits for a while again.  Have you tried a compression check on it?  Maybe let us know a little more about the bike like miles, etc.

[OakBehringer]

Bike has under 5,000 miles on it, but that doesn't really mean much when it's 34  years old. Who knows how it was maintained for that time.

I did a compression test at the beginning of the summer when I bought it and it was good, but I don't remember the numbers. I don't even remember if I did it hot or cold. What steps should I take to figure this out?

Thanks,
Adam

[Johnie]

I would say that a 74 with 5,000 miles has been sitting a lot.  All those years of sitting will dry those valve seals out pretty good.  If you only have the blue smoke on start up and not while running, and you have that good compression I would still point to those valve seals.  But...I had this same situation on a 1981 CM400 Custom I bought with 1,300 miles on it.  I took the head off and sure the valve seals were bad, but I put rings in and honed the cylinders as long as I was that far into it.  Good winter project and best of luck with it.