Hello they can be little bu**ers to start some times. But providing that the bike worked fine last time used then do the following...
first make sure that the fuel mix (2 stroke ) has not settled out give it a good shake first before turning on the fuel tap. then without the choke ( lever down) give 4-5 pulls on full throttle, then raise the choke lever to the top, use a very small throttle opening and give 4-5 hard pulls if it has not started to fire then lower the lever again and try another few pulls with full throttle. if it does not start, then remove the spark plug and examine.
a. its wet (possibly to oily mixture) or leaking float flooding engine, or too weak a spark under compression (verify spark gap, should just be able to slide thumb nail into gap ajust if nessessary) check cut out switch is not shorting out or stuck....
b, plug is dry, no fuel reaching cylinder (either low fuel level in tank, or fuel tap not working or in wrong position) Main jet in carb blocked through dirty fuel / dust getting into fuel tank. or if the bike had been standing for some time with fuel in tank then possibly the fuel in the carb or fuel line has evaporated and there is a thick oily plug stopping new fuel reaching the cylinder. clean out all the fuel lines tap included verify tap position on/off dismantle and clean the carb, possibly a stuck float needle (just dismantle and clean, do not re-ajust float level to compensate another fault!)
finally check timing.. ps allways take up the slack in the start handle cord before pulling to start, getting annoyed and yanking violently at the starter cord will ruin the starter ratchet, when that fails nothing will start the engine. be patient have a cup or tea and start again.
colin
April 2010