[GSjimmy]

OK, I'm officially stumped. Have the motor built since February, butcan't get it to fire up. Have fresh gas, fresh plug, verified the timing 3x, set the point gap to .016, Verified TDC on the piston vs. the "T" mark on the flywheel. Cam is set with the lobes in the down position (8 & 4 o'clock lobe positions)
Carb is a 2003 XR100 unit.
Plug is NGK CH7HSA
Have tried starting fluid as well, nothing.
Best I have gotten is a pop out the carb or pipe.
Jim

 

[Bean573]

Have you done a compression test?

 

[GSjimmy]

OK, went back to totally stock. XR80 jug/piston/rings/cam, Same result kick it and nothing happens. Now I did notice a very small contact spot on the piston, exhaust valve. Previously had verified that the head held liquid to check for a bent valve.

So the issue has to be the head, can hear a very slight woofing sound when kicking it over. Anyone have a known good head for sale?