Motorcycle Repair: help, yamaha tzr 125, fuel air mixture

Question
hi ,  i have recently purchased a yamaha tzr 125 r , not the import but the 4wl or 4hl version.
the bike ran fine and sent it in for an MOT and came back a week later , bt i took it for a spin and it died( sounded like it ran out of fuel)
and since then iv had no luck , i got it started the other day but when i reved it over 4000 revs it jus bogged out and that was that.
its has a brand new ....

stater motor
coil- ht lead and spark plug
battery

but still it will not start , the fuel is getting into the carb and it only sparks when it wants to???
is a big problem for me any advice

many thanks matt

Answer
Hi, Matt. You are certain the fuel is getting to the carb, but what happens after that - are you sure there is sufficient fuel/air mixture getting to the cylinder? Is the air filter clean and unobstructed? Fresh gas in the tank and a recent draining of the carb float bowl? Choke mechanism is set properly and not stuck in the closed position?

If all the above checks out okay, then concentrate on the ignition system. After an unsuccessful starting session, have you pulled the spark plug to check its condition? If it is wet with gas, then something has failed to give it spark. As you've replaced the coil, plug and wire already that leaves the ignition box and the pickup plate (or sensor, I'm not sure what Yamaha uses on this model). Either one or both of them could be at fault and the unfortunate thing is there's no quick way to test them other than to replace them with new units.