gsx 250 cyl head

[hugo151]

hello, i have 2 cylinder heads , one has 3 studs broken off in it but perfect valves & seats, the other has perfect threads but a mushroomed over inlet valve end & 3 of the exhaust valve seats are broken up & beyond grinding in. whats involved to re-cut the seats? or should i forget this head & concentrate on getting the studs out of the other ?

[pete]

I reckon dealing with the studs would be a lot more straight forward...

[Mekanix]

+1 Take your time and drill small to large. If its not cutting, Get another bit, Cobalt bits work great but you have to go slow and let it cut with some fluid. Speed up for a second and they are toast. Grind the top of the bolts to a nice flat spot and then hit it with a center punch to start the drill off right. Try to keep it straight. You can correct a bit if you go off but you have to do it while your still using a small bit because the larger one will put you into the threads.


The other option that works is to Weld a nut onto the end of the bolt and just wind it out.
The heat helps to separate the bolt as the aluminum expands. Just remember to protect the port from the welding spatter.

Recuting seats isn't that hard but you have to have the right tools to do it. A machine shop should be able to do it but it will cost more than the studs will. And you would have to fix the mushroomed head just to get the valve out. Witch means you might need a new valve too.

So stick with the broken studs Id say.

[hugo151]

cheers, i came upon a second hand cyl head today at an auto jumble for £20, the threads were good + so were the valve seats, 2 of the inlet valves were a bit pitted but may lap in, if not, i'll rob them off the other heads. the other bonus was the inlet rubbers were soft, my others were rock hard. i will try to drill out the other head as you suggested. thanks.

[Mekanix]

Go with the valves that need the least amount of cutting so you don't wear out the seat.