Where Jetting issue

[greco400]

Now that it is Cold out side, my 400 with 170 dyno jet everything in carb is brand new floats ect. well in the summer it ran fine like a champ. now that i got cold my qaud run's like crap on top end some days it will run fine some days it will run like crap.
to half trottle its perfect just on full throttle

my plug is black just carbon up no wet spot, I check for air leaks came out negative so i took my air box off and started it up and when punch the trottle fuel squirted in a heavy mist out the carb and starts to cut out.

any idea's go down on main jet? or needle setting needs changed

thank you

[2004exrider]

Just for kicks, try putting in the next size jet. Sounds to me like your running a tad lean, from 3/4 throttle to full is when the main jet kicks in.

Jimmy

[greco400]

thanks for the reply im just confused on how some days it will run like a dream next day just like crap i dunno.. i'll try something tomorro

[ccd]

Originally posted by greco400
Now that it is Cold out side, my 400 with 170 dyno jet everything in carb is brand new floats ect. well in the summer it ran fine like a champ. now that i got cold my qaud run's like crap on top end some days it will run fine some days it will run like crap.
to half trottle its perfect just on full throttle

my plug is black just carbon up no wet spot, I check for air leaks came out negative so i took my air box off and started it up and when punch the trottle fuel squirted in a heavy mist out the carb and starts to cut out.

any idea's go down on main jet? or needle setting needs changed

thank you

If the plug is black, I would think that is too rich. But if it runs worse when it's cold, I would think it's too lean. I would try to run it 1/2 to full throttle for a stretch and pull the plug. If it's black, you may want to go down a jet size. JMHO.