No 1 grandson was riding his old DR when it made a rattle and stopped. He pushed home and lifted the head to find this. One of the inlet valves had broken and made a mess before the engine came to a sudden stop. I knocked out the rest of the broken inlet valve seat and gave the head a clean up in the blaster. The standard seat has 30mm od, so I bought a 31mm od seat so I could machine to the right size. I heated the head in the gas bbq to 200deg and welded the damaged area. Then using a boring tool with a 5mm spigot I bored the seat cup out to 30.5mm to get a good seal. I turned a piece of 32mm bar down until the new seat was a tap fit to hold the seat so I could turn it down to 30.65mm. This gave me a 0.15mm interferance fit which is about what most head inserts work to. After removing the seat I turned the bar down a bit more to be a loose fit of the seat and drilled the other side to fit onto the boring bar. This I could use to fit the seat into the head. I put the seat in to the bottom of my freezer overnight and next morning heated the head in the bbq again. Three light taps had the seat installed in the head and I covered with a rag to let slowly cool. Some more time with the boring bar to get the seat nicely flush with the head and a run across the sander to flatten the gasket surface and cannot now do anymore until the new set of valves arrive and the seat can be finally cut.
Valves arrived, so finished the seat to suit the valve face, cleaned in laundry tub and put together. Still waiting on piston before can run it.
