Motorcycle Repair: honda c50

Question
hi I have just restored a 1968 Honda c50 it was running yesterday but it will not start today it has a strong spark,i have cleaned out the carb in a sonic cleaner and rebuild it but it will not start would you have any idea thanks gary.

Answer
Gary, the basics of the 4 stroke engine are

Compression
Fuel at correct mixtures
Spark at the right time
Air to mix the fuel inside the carburetor..

You should be measuring about 150+ psi compression.. if not check your valve clearances next

Make sure your spark is coming at the right time and is steady during cranking. Intermittent spark at the plug is usually a sign of either a loose wire connector, bad condenser or weak coil... or low battery voltage.

Check carburetor for all jets in place, mixture screw set to specs, slide needle clipped and secured. Look at intake manifold gaskets/o-rings and check for any stripped thread holes at the cylinder head that allows the manifold to work loose.

Try running without the air filter hooked up.

Sometimes the spark plug will fuel/oil foul on initial startup, so try a fresh new plug if all else fails. The spark plug cap should either be zero ohms or 5k ohms at the most.

Bill Silver