Exhaust valve snapped

[plpitts1]

I have a Honda GX390 QXC9 GCAA 3295657. The exhaust valve snapped off, spun around and the stim was driven through the piston. The head has a few dings in it. Would this be something that would be worth repairing or should I get a new motor ($700.00)? Should I replace the Head? My concern is what may have caused this. Looks like the filter had never been changed on this walk behind concrete saw (carbon buildup on the head, filter completly full of dust), and the oil was black as I have ever seen. I pulled the crank case cover off and all seems ok in there at a glance. Push rods, rockers, ect.. all seem to be ok, just the one valve and the damage to the piston and dings in the head. (I would replace both valves). The head would be the most expensive part.
Thanks,
Pat

[RoyM]

I would expect to replace the head, the guide is likely excessively worn and they are not serviceable. Concrete saw engines work in a brutal environment, couple that with lack of maintenance service life is short. Check the bore for taper as well as the crank and cam for wear.

[KE4AVB]

Really depends on the overall condition of the engine as to if it should be repairable or just replaced. Got weight parts cost and labor against the cost of a new engine.

I would expect to replace the head, the guide is likely excessively worn and they are not serviceable.

Roy, This engine does have over sized valve guides available (they are listed as optional). Haven't worked with them so it would take someone familiar this engine or have access to the service manual tell what is oversized about them and how they are installed but they are shown being held in with retaining clips.

Also aftermarket cylinder head is available for around $120 but doesn't include valves or related hardware.

[plpitts1]

Thanks, I appreciate the input, I will do some pricing and talk to the owner
Thanks again
Pat