How do I check the timing after I put a new head gasket on, and now it will not start, I have got fire on the spark plug, I took the carb off and cleaned it, Still will not start

The most common cause is a wood chip stuck in the inlet or exhaust valve.
Check the compression.

Check gaskets / seals / piston rings as it sounds like oil contamination is fouling the plugs.

take plug out put a very small amount of fuel down cylinder, plug back. does it fire up??

hello david,Has spark, fuel trys to start,could be bad fuel as old,water in fuel or tank,gas container with debris,crankcase over full on oil and gas,bad coil,bad plugs,low compression,blown head gasket,valves adjustment if ohv, these are the things i would check if i had it here in the shop,hope this helps,

if you have good blue spark and it fires when fuel is added externally , then the problem is fuel flow through the carby
have the carby professionally overhauled or get a new carby
make sure that the gasket to the manifold / head is in good condition

the ignition cant fail from sitting, perhaps the kill switch has corrroded, always put a spark plug in and ground it to the head when checking for spark , also check with a new spark plug

Your timing is off. Did you have the distributor out when you changed gaskets or maybe took the plug wires off?

First you could make sure you have spark. Take the plug out and then plug it into the black wire. Set the end of the spark plug near the frame of the lawn mower. Pull the cord one time to see if there is an arc from the plug to the mower. If you have spark, I would put the plug back in. Before putting the plug back in I would spray a little bit of starting fluid. See if it will fire up with the starting fluid in there. If you have a true good spark, it should fire up. This may be enough to get some gas going in there as long as you have the lines hooked up correctly.

Do you have fresh gas in the bike? Try changing the plugs with new ones and check for spark. You can do this by putting the new plugs on the plug wire and grounding it to the head on the engine crank the motor over you should see a bright blue spark. Check one plug at a time. No spark check the ignition wires and coils. As for the oily plugs it could be they are just fouled caused by either flooding the motor while trying to start, bad plugs, week coils, bad gas, poorly adjusted carb's. I would start with the plugs and work my way back to the carbs. Still fouling the plugs after all that start checking the engine, ie compression check ect.

check the vacuum pipe is in place on carb