Motorcycle Repair: Honda z50, honda z50 engine, piston kit

Question
I have a honda z50 engine with a 70 cylinder and piston kit. I also ported the 50 head, and put a 20mm carb and monster cam with longer duration. My problem is that it ran once I installed the cam, but was working through rejetting the carb to match my changes. On a test run, I slowed down to an idle and the bike shutoff. Now I cannot get the bike to start at all. I checked timing, spark, etc. One thing I noticed, is that near the end of the intake stroke, there is a slight blowback out of the intake port. I'm not sure if this would cause it not to run, and if so, what may have changed and caused this, as it was running prior to this with all of the new parts. I also cleaned carb, and replaced breaker points, and plug. It seems to be a fuel related problem. Please help me if you can!!!

Answer
Brian, sounds like the intake valve is bent or hanging open. CHeck the compression on the engine. If you don't have a compression tester, take out the plug and try to hold pressure in the cylinder with your finger as you kick the engine over.  You have to put some force on teh plug hole to hold back 150 psi of pressure.  If it doesn't blow your finger off the hole, the engine is low on compression.  

Regards
Rich