Can start now on choke and will idle ok for a while then revs start increasing on their own? Bogs and miss fires higher up the rev range? Tried a Jetex 22mm but the symptoms were worse, gone back to the dellorto. like I said it ticks over for a few minutes now off choke, then the revs increase on their own up to sort of half throttle? Worn slide? I have a 25mm dellorto, but got no manifold for it yet...