Smoke from the LH exhaust

Hi There
One of my friends own a 750 Codo, I did a full engine rebuilt last winter, the bike is goind very well so far, don't smoke when riding, only when the bike stay on idel for a wile and you open the trotel, then blue smoke come out the LH exhaust for a very short time.
What can it be please?
Yves

Leaning on the side stand? Oil in the head flooding the left hand inlet guide ?

Full rebuild with new guides and seals ?

Fast Eddie said:

Leaning on the side stand? Oil in the head flooding the left hand inlet guide ?

Click to expand...

No, On center stand

Torontonian said:

Full rebuild with new guides and seals ?

Click to expand...

Yes, all new

Fast Eddie said:

Leaning on the side stand? Oil in the head flooding the left hand inlet guide ?

Click to expand...

No, Bernard always keeps his bike on the center stand, so that can't be the reason. As Yves says, the bike runs perfectly well and doesn't smoke at all. But if it is stopped for a little while (say one hour) and started again, a substantial puff of blue smoke comes out of the left exhaust for a few seconds. Rather bizarre.

You didn't say how many miles/KMs are on the new engine, but if it has less than 1000/620 it may still need more running time and more aggressive use of the throttle.

A leak down test will tell show you if there are differences in the health of right versus left cylinders. The visible emissions you see at idle are, more than likely, present while running at speed just much less visible due to a lesser A/F/O ratio.

There are many other possibilities, none of which will be pleasant to deal with; I'm sure that the Doom-Sayers will enumerate them with gusto; I just hope that you didn't assemble the engine under a full moon...

Best wishes

The first and easiest check is to see if the rocker spindles are oriented correctly. If they are in wrong the oil enters the head faster than it can drain out. Also make sure that nothing is impeding the oils gravity flow back to the sump. Start easy stuff first.

Could be the spindles/poor oil drainage, as noted. Oil smoke when accelerating from idle normally indicates valve guides/seals OR, on our Nortons, the spindle/poor drainage issue.