Hi Datz,
Make sure the spark plug [if C7E] has an extra washer, because the exhaust valve can hit the tip on certain versions of the head. The most common failure is the ignition sensor. As long as the green wire from the coil is ground and the green wire from the CDI is not grounded the ignition should be ready to fire. Never assume the spark plug is good, as many have spent hours looking for a problem and it was the plug. A good sub for the plug is an Autolite #4303.

When I designed the vent system the PVC valve needs to be level to work best. The PVC valve is gravity contolled.

Have fun,
Quenton