Smoke from right pipe after sitting for a week

Hello, a new thing that I need to ask why.
If the bike has sat for a week on the side stand and I start it, it blows smoke out the right side pipe.
It clears quickly and doesn't do it again unless it sits for a while.
Why?
The right side is higher than the left, which doesn't smoke.
It shouldn't be guides as I have only just had them replaced.

Graeme

I forgot to say it's a MK3, if that makes a difference.

Graeme — is your Mark 3's anti-sumping valve working? After a week of sitting on the sidestand, you could drain the sump, see how much oil there is, re-fill the tank and check if it still smokes from the r/h exhaust. I wonder if, when sufficient oil collects in the sump after a week, the crankcase pressure on start-up is forcing some oil past the rings in the right cylinder, if they are slightly more worn than the l/h cylinder? The other thing you could do out of curiosity is to whip off the rocker covers and see if there is oil pooling around the valve guides.

Dave

Yep, it just needs to have the sump drained, then taken out for a 20 minute ride.

...make that a 3-hourr ride; there's not much point in a 20 minute ride.

I have had a similar problem with a number of my Commandos over the years. It has been oil wicking down beside the exhaust valve guide and into the exhaust port. It does not smoke once the bike is started and does not do this consistently. if the bike has not sumped then this is the next possibility.

Thanks,
What is an acceptable amount of wet sumping over a week? (if left on the side stand.)
I have seen the right exhaust valve stem damp, looking through the exhaust port.
Graeme