No compression i replaced broken key way in main shaft. i hoped that was problem.but still no compression so i checked valves and they function fine. what else could it be? pleas and thank you for any knowlage on this.

Valve lifter on cam shaft faulty, either stuck or spring broken.

if you have no compression then that means that the pistons are not compressing the air fuel mixture on the compression up stroke
This means several things
valve not seating or sealing ---bent valves
valves not opening --- broken chain/belt
rings broken-- holes in pistons
badly warped head/s and destroyed head gasket/s
check to see if the cam shaft/s is turning,
have a compression test ( dry and wet ) done by an accredited mechanic-- mechanics that do not know why there is no compression may not be mechanics ---to see exactly how much compression you have and on what pistons.

have a compression test done to confirm your suspicions. If the compression is low on some but better on others it may be valves . If the compression doesn't alter check the cam shaft is turning ( broken timing belt)

IF the valves are sticking open then the bad news is that they are probably bent and jamming in the guides.. I would guess that in reassembling the head they were not aware of the cam shaft timing and turned the crank when the cam was not positioned correctly hence the bent valves. With the compression readings you have it points directly to bent valves . They probably fitted the cam shaft then put the head on which will result in the same bent valves. Sorry for the news but my advice is to get the valves replaced then get hold of a work shop manual and do the job according to the book. At least you will wind up knowing more that the guys that didn't Best of luck.

sounds like you may have a broken valve spring. Do a compression test as you crank it. If the valve spring is broken, you will get nearly zero compression, it will turn over very easily and this would explain a couple of backfires.

you need to do a compression test on all cylinders. All cylinders should have about the same amount of compression with a minimum of 120 psi.
if there is a major drop of compression in a cylinder that means there is a malfunction in that cylinder(bad valve, broken rings, etc
if there is a major drop in compression between 2 cylinders then that means you have a bad head gasket.
if all cylinders read 0psi then you have a broken timing belt
If all cylinders read about the same then you need to check the timing and make sure the cam(s) and crank shaft are still at top dead center (TDC)

I've had a few of these engines break the cam shaft after cylinder #4. meaning #5 & #6 have no compression, but also no oil pressure due to no oil pump drive from cam shaft. 2 out of 3 times the engine was toast. If it truly skipped the timing, then you will need a timing chain and sprockets. When the timing skips or the cam shaft breaks, the pistons will definitely hit the valves and bend them, thus no compression. I'd recommend tearing down the engine yourself and determine what went. To check the cam shaft, remove the front valve cover and watch the rockers for cylinder #6, if they don't move then broken cam shaft.

valves are out of adjustment. reset them and it will do fine.

the key word here is the sound, engine must have compression, put your hand over the carb and try to start, if it trys to **** your hand then you should have enough compression, if it doesnt then you probably have a broken valve- hope that helps

either a new clutch or timeing belt. hopefully the trasmission is ok