nick h

...doin it 5 years now.? never had a bad result ever.now im currently working on a customers 1991 honda xr 250r and im building it up for a desert/woods enduro racer.he threw a exhaust valve in it.valve head busted off the stem and got wedged into the valve seat.now the only trouble in my 5 years of building racers and trail bikes is getting this valve seat out.never had a valve get wedged into the seat.the seat surface is too badly damaged to resurface.now i have all new valve seats and valves.now what is the best way to get these seats out?ive never had to remove one only resurface them.anyone know what the best way to get one of these out?

tomcotexas

You have a problem you should not even think about trying to repair yourself. It is a job for a machine shop only. If you try to heat a head to remove a damaged seat, you are likely to do serious damage to the head, as the seat is often deformed by the broken valve head being jammed into it. The only way to properly remove it is to bore it out, using proper seat repair equipment. The hole will most often be larger than standard when this is done, so a oversized seat is required. Then comes the problem of getting the correct interference, so the seat will not come out. I am not trying to tell you all is lost, as it is not, but find someone who can properly do the work, and he cam fix it good as new, for a reasonable price. Now, if you please, I will tell you how it is done. As I said, the head is bored out, to get a good clean hole, a bit larger than standard. Then, an oversized seat is obtained, or a seat blank, it is machined to prober depth, bore, and angle, then the OD is machined to 0.007" larger than the hole. A proper sized pilot is obtained, (make sure the valve guide is in good condition, and tight) and that a proper sized driver to hold and insert the seat is obtained. Heat the head to 450F, and the seat will go in, with no more than a tap. Remove the pilot, turn off the oven(never heat with a torch), put the head back in the oven, and let it cool to room temp by its self. When cool, reinsert the pilot, use the seat driver, give the seat a good solid rap, to nsure it is seated completely in the head, and you are ready to cut the new valve seat surface, and are good as new. If you have questions, you may contact me.Tomcotexastomcotexas@yahoo.com