having probs with an old suffolk engine 98cc the valve seat keeps lifting from block i can take the head off and give it few taps back into down into its position when run after that operation the probs start again after 10 minutes running any ideas how to stop it coming from its position

The best way is to make or get an oversize seat ! You MAY be able to drill right beside it and put a set screw in to hold it, but that's a gamble.
Pops

thanks pops will see what i can do regarding your sugestion

Have you tried using a pointed punch and punching around the seat in a circle to hold in seat? Works on Briggs engine.