i know this has nothing to do with quads but i need to know so here it goes..........my xr100 topend blew so i got an xr80 head from my cousin but i need to know if that head will fit on the rest of the engine i heard it does but... the combustion chamber is too small can it be ajusted so that the cylinder won't blow out of the top of the 80 head

 

You could try to have it machined but I think it cost more than what it is worth.

 

how much does it cost to get it machined?

 

Ask this on Thumper Talk at; http://www.thumpertalk.com/forum/index.php
on the XR80/200 page and you will get correct answer.