250r timing

[3leggeddog]

is it possible to get the timing off on the 250r's?i ask because since i replaced the crank seals,it will back fire,or pop when i kick it.almost like it is out of time,or
loading up.is it possibley a carb problem?i have noticed that it also has a real bad transtition stumble now too.but i recently rebuilt the top end with new porting,so that could be jetting?

it's wierd.it kicks bask real hard,and won't fire.but if i hold the throttle wide open when i kick it,she fires right up.any input on this is great,thanks guys

[phil53]

the keyway for the flywheel could be sheared or stuck down in the groove all the way which will allow the flywheel timing to be off. both have happened to me. too much advance and it sprained my ankle trying to start.