spark problem or fuel problem?

[jamesbebby]

hi, havin abit of trouble with my kx250 '06.

was ridin along fine and all of sudden it cut out about 200 meters up the road push it back & got a new spark plug and it start went back up the road again & it cut out, so i clean up 1 of the plugs and it fire up left it runnin & everything was fine start pullin back the throttle and it die.

why is it cuttin out is it fuel problem your is the coil or spark lettin me down on high revs?

cheers james

 

[ellandoh]

fresh top end?
good reeds?
clean air filter?
warmed up before riding at all?

if the answers are yes then i would say fuel problem

search DRN for spankys jetting guide

 

[jamesbebby]

fresh top end? no
good reeds? yes i think so
clean air filter? of course
warmed up before riding at all? yes

this bikes had about 15 hours use in its life.

cheers james

 

[ellandoh]

how far was the throttle cracked open when riding

0 - 1/4 turn in the air/fuel screw 1/4 turn til running better
1/4 - 3/4 drop the needle 1 position at a time til you get it running good
3/4 - wide open buy a smaller main jet

this is all assuming the plug was wet fouled
for better info goto

http://www.dirtrider.net/forums3/showpost.php?p=1329233&postcount=8

http://www.lmgtfy.com/?q=2+stroke+jetting

 

[whenfoxforks-ruled]

How long has it had the tank of gas sitting in it? Dirty carb? Vintage Bob

 

[sharky243]

Start with checking for good fuel flow from the tank. Check ALL vent lines for any blockages. Drain the carb bowl into a container and look for contaminants like water. Cleaning the carb. wouldn't be a bad idea. Make sure your fuel is clean and fresh. while the carb. is off, remove the reed cage and inspect the reeds for cracks, chips, or warpage. Reassemble the bike and test ride it. If the problem still exists, check the compression (norm ave. 150 psi). Start checking the ignition system out, you may have weak spark which will breakdown at higher RPM's. There is a series of voltage and resistance test to perform on the system, refer to a good service manual for specs. and proceedures.