Smoking exhausts at start-up, Commando 750 1971

Hello.
At start-up both exhaust blow lots of white smoke for a minute or so. Once on the move the smoking stops & doesn't start again until the bike is started again after standing for few hours & is then.

The engine was totally rebuilt about 1500 miles ago and has only had these symptoms in the last few hundred miles.

Initially I checked for wet-sumping. This was definitely happening but has now been cured, but this did not resolve the problem.

If the small amount of oil now gathering in the sump is drained, before start-up, then the smoking is significantly reduced.

I also noticed that the crankcase breather pipe (connecting from left hand side of crankcase below cylinder) is spluttering emulsified oil into the oil tank after a 20 min.

Any ideas?

Thanks
Mark

Have you retorqued all the head bolts, and then checked the valve clearances now some 1500 miles after the rebuild?

How have you fixed the wet sumping? Installed an anti drain valve in the oil line?

Others than myself hopefully will comment on the emulsified oil issue.

The wet sumping has been stopped with an anti-wetsumping valve. I have not yet re-torqued the head or checked the valve clearances. Are you thinking that the valve clearances may cause the smoking at start-up?
Mark

even if there were no smoking, absolutely you should retork all head bolt and check vales since you have not done that since putting head on
I would have done both at 50 miles and again at maybe 500

Just going by this description i'd wonder about valve seals.