There's a couple of things to try!
First, go to Central Hobbies and get an oring set. You've started the process by replacing a couple of gaskets but you need to replace them all! Pull the regulator assy and check the diaphram for tears or pinholes. If you want to do it right then by one of these also and replace it.
Pull the cam cover(right side of engine), pull the top rocker arm cover and remove the right(exhaust) pushrod. Go back to the cam and push the lifter up so its out of the way. Put the piston at tdc and check that the dot on the cam gear is straight up!

You can do this when you are replacing the o rings because you are gointg to have to pull the head to replace the push rod cover orings. Remember to replace ALL the orings. Teh motor should perk right up!