I have a 2007 yz250f and the kick starter locked up if i remove the spark plug boot i can kick the starter over then put boot back on plug then i can kick it over and it will start then die about 20 seconds later then it will cut out then i cant budge the kick starter over until i remove plug boot and repeat the process ?

SOURCE: YZ250F kick starter is backing out of gearbox

Go to the site below and download a free factory service manual.

http://www.carlsalter.com/motorcycle-manuals.asp

Kick starter starts at page 175. I am certain this will help.

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SOURCE: Tuono R 2007 Engine cuts out when fan kicks in and won;t

By fan you mean the radiator fan? If so try the following. If a coolant temperature of between 239oF(115oC) and 275oF(135oC) appears on the multifunctional digital display, stop the vehicle and leave the engine running at 3000 rpm for about 2 minutes, allowing the coolant to circulate regularly in the system. Then position the ENGINE STOP switch to "OFF" and check the coolant level to make sure it is ok. If after checking that everything is ok it still does the same thing the you should probably go to a mechanic.

SOURCE: Engine seized?

was riding my bike at 40 it cut out will push start but wont kick over!??help plz!!!

SOURCE: 03 yamaha yz250f wont start carb prolblems? it

Could be bad fuel, and/or faled plug.