Motorcycle Repair: RT! 360 yamaha, 1970, cause havoc, tiny particles

Question
started up for 15 min, now won't fire unless i put gas in the plug hole, then it goes full throttle for 10-20 sec.and i turn it off. can't figure if it's the carb, throttle cable, etc.  I disconnected the oil pump, put a 40:1 mix in the gas tank, use a hotter plug, replaced the decomp. plug with the old sp. plug. seems like the cable sticks in the carb...?

Answer
Ben,
 It's possible the throttle cable and/or slide is not functioning correctly.  Remove carb from boot w/ throttle cable attached and witness the slide through the barrel as you move the throttle.  If this is ok you may just have an improperly adjusted carb.  If your floats are set incorrectly, or they are filled with fuel, or your needle valve is stuck shut, or your main jet is damaged or obstructed, you will not get any fuel.  Here is some info I've given others on cleaning carbs:

Disassemble, clean all jets and orifaces with solvent and COMPRESSED AIR ONLY, use NO wire or picks to clean holes/airways. Rebuild carbs with new gaskets and make sure your floats are set correctly. . Do not overlook the float level, be very sure you are not starving for fuel. In relation make sure fuel flow is unobstructed and use a good in-line fuel filter from the tank to the carb. Even tiny particles in the fuel can get logged in critical areas and cause havoc.

Hope this helps,
Mike