I am rebuilding a Suzuki LTF-250 engine. I was installing the valves and the spring compresser slipped off of the spring which in turn scored the cyl head surface. I can feel the score with my finger. Do and can i re-machine the surface. Also is there a specification for how much i can get machined off of the cyl head ? Any help would be appreciated !

 

I would simply take the cylinder to a local machine shop and take their advice. They have probably seen the same problem many times over and know what it might take to correct it.

 

If you scratched the cylinder itself then have it checked out, if its just a little scratch in the head, run it. shouldnt hurt anything.

 

If you have scored the sealing surface, the scratch needs to be taken out, otherwise you are looking at a potential blown gasket. Finding a machine shop that can handle small objects like yours is going to be difficult ( I know no one in my area of the world can handle small heads like these). What I ended up doing - suggested by my machinist - is buying a thick plate of glass (8X11 or so), and some self sticking sheets of emory cloth (or even sand paper) available at your local auto parts store - medium to fine grit. Stick the grit to the glass (a naturally flat surface) and work the head in a circular motion on the grit a little at a time to clean up the surface of the head. On 4 wheeler (or motorcycle) heads, I never go more than 0.005 - 0.006", so you may need to take care to see how much surface area you are going to have to remove first. You can monitor the amount of surface area you've removed by marking 3-4 spots around the head and using a depth gage or caliper to measure the "lip" originally, then periodically as you "machine" the surface of the head. I've used the glass method many times over the years, until someone gave me a large slab of marble that works even better because of the weight.