Rebuilt Honda trail 90, Valve stems cupping now

[Motorhead]

My daughter and I rebuilt a nice Honda trail 90. We bored it to the next step, had a COMPLETE valve job done including replacing the valves. The engine has 300 miles on it and I noticed that the valve lash grew and it ticked. The CAM is perfect.
I have been working on these things on and off for 40 years. I was shocked when I saw that BOTH valve stems, where the adjuster screw contacts, are now cupped! The only thing that comes to mind is that I had the ignition timing too advanced. It did NOT ping at all. The valves were supposed to be NOS Honda valves. I initially set the valve clearance at . 002in which is factory. Any ideas???

 

[Bob4x4]

I haven't done a lot of 4 stroke bike stuff,but I did have a fleet of ATS 185s's and a 200x for the kids. Built them all with big cams,matching springs, and ported the heads,used lots of cam lube and did not idle them at initial start up. Never had any unusual wear. The cams had so much lift,had to do away with the compression releifs. Do you have good oil flow to the head?

The 185's and 200s have oil flow up the studs to the head. I would guess the 90 is the same.



Bob

 

[Motorhead]

Bob, Good oil flow in the engine. I am now even running synthetic. The adjuster screws were also replaced and inspecting them, they look great. I am just going to have to pull the head and replace the valves.

 

[Hoefler]

Valve stems are soft. The end is supposed to hardened because it is a wear point.