Few Questions About Honda 125s

ok guys, i believe the vavles need to be seated in my honda 124cc motor, the problem im having is that i re ringed the motor put it all back together and now it aint starting, i have moved the timing to every way it can go and the same thing, its either got no compression, or its got compression but its blowing back out the carb but want crank. So does this sound to yall like it is just the valves need to be seated?? and if they do i heard you couldnt grind these valves like you can a car valve, is this true??

no its a 4 stroke 1981 honda XL 125s if i put the timing one way which is the marks on the cam straight up and the t on the fly wheel straight up i have no compression, if i put the t straight up and the cam dot pointing straight down at it i have compression but its blowing back out the carb, i was thinking maybe the valves needed to be seated becuase they did have some sharp edges on them, but im unsure if you can grind these valves or not.