jetting problem issues

[herbert]

will someone please help me 03 kfx400 just installed full yoshi,k&n filter , air box lid on,165 main jet plug was burning good, throttle response was perfect, no studderinggoing through all 5 gears no back firing. ran perfect for 5 to 6 hours of good hard riding then it started to back fire and studder trough every gear. i dont get it what happened all of sudden:confused:

[YFZ450Ridr]

i run a 175 main with just a slip on, uni filter, and removed airbox lid. if it ran fine and then started to crap out you could have a jet clogged, water in your gas, or even bad gas. ive had bad gas before and it blubbers and back fires and wont hardly run, kind of like what you described.

[hang1p]

good call its probably not the jetting if it ran good for 5-to 6 hours water in gas or you hit a big puddle and your sucking water threw the air filter or maybe a loose vac. hose on carb