I always thought that Panhard valve seats were immune to valve seat recession. I was just stripping down Brian’s rear cylinder, when I noticed the exhaust valve sticking when I removed the collets. This is the reason why.




The exhaust valve had receded into the head by about 1mm in places, and the seat now looks like it has two 45 degree faces cut in it, so it looks like a new valve seat is in order, or it might be quicker to swap out the cylinder. I have a valve seat, but it means heating the cylinder to about 380ºC, which is when the differential expansion rates should loose their interference fit, but it looks like I will have to do the valve guide too, as it’s rocking once the valve is off its seat.

Looks like the engine liked it oil, but it did have a broken piston ring, so that won’t have helped. Time for some barbecue cleaner