I know this sound stupid but it is the only way i can explain it!
On my Sportster every now and again when it revs there is a puff that coms out of the gasket part between the rocker and head ?

Is this a common Problem i already fitted a new gasket and the head was skimed ??

 

I think we may need a better description here. When you say puff I would think you mean smoke right? And if its smoke, i don't think your leaking from the rocker/head gasket cause you'll have oil comming out then if it's on any of the rocker gaskets for that matter. What side of the in relation to intake or exhaust do you see it. If you see it on the exhaust side, it's probly the exhaust gasket not sealing and its spitting a little smoke upward and makes it look like its coming from the rocker gasket.

You ask if it's a common problem....well the rocker/head gasket is very common to leak....but like I said it'll give you a little trickle of oil comming out, not puffs of smoke. There's also the possibility that you do have a little trickle of oil comming out, and its dripping on the exhaust to create the smoke. Sometimes the oil leak can be very hard to spot, so look hard, get a flashlight. Ok, welll good luck, hope you figure it out. Keep us posted on what you find.

 

ok i have had a closer look it seems to happen when it is stood and you rev it but it looks lke it is coming from the head gasket there is a littel trace of oil but not alot