well ppl hows it going. i was bore lastnite and strip the head of my mini engine and thank god i did due to the condition of the pistons surfaces. just want to now wat dia would a 1275 piston be, i ruffly measured 71mm can any one help me out? and would a inlet valve of 34ish be good? should have photos if i can get camera to work

depends where you measure the piston, and also.. measuring roughly isnt really accurate enough.

same goes for valves. Bigger isnt always better.

what is actually wrong with the piston crowns? if its just a carbon build up thats normal.

yeah but there is a good 4mm in some places of the pistion and was just out at the head there and one of the chambers was filled with carbon and on each of the valves in it a good 4 mm build upo as well.

Standard piston sizes can be found in the Haynes manual.

34mm inlet valves are too small to be any good on a performance A series. 35.6mm inlet and 29mm exhaust a good place to start.

I sent U2U a while back detailing what I would, and have many times, used as a good alround road spec.

ok roger. but is it normal for that amount of carbon build up i had to take it of with a chisel and the exhaust valves are covered in a whitish cake

Sounds like it's been burning oil for a long time. Check out minisport at padiham for some head specs.