Troubleshootin, help?

[Raptor4439]

I was on my 440ex at the track and it was doing the usual, spittin and sputterin. I drove it up to Gary (Yamaha dealer owner) and he said that it was the ignition screwing up and not the jetting, is he right? im running 138DJ and 3rd clip position on the dyno jet needle with the stock exhaust. With that jetting setup the spark plug tip doesn't foul black or anything, it stays a good light brown. I just feel like im not where im supposed to be because everyone else is running around a 170MJ :(

[cals400ex]

a 138 seems small for a 440. you may be getting a light brown color on the plug from the needle, clip position, or pilot jet/fuel skrew. where does it spit and spudder at or what throttle range?? you could have a bad ignition. i would also make sure your plug is in good condition.

[Raptor4439]

Originally posted by cals400ex
a 138 seems small for a 440. you may be getting a light brown color on the plug from the needle, clip position, or pilot jet/fuel skrew. where does it spit and spudder at or what throttle range?? you could have a bad ignition. i would also make sure your plug is in good condition.

from 3/4 to full it sputters, I used a brand new plug after I thought I jetted it right.... it feels like after it runs a while it gets worse and worse, it spit and sputters more. could the ignition cause this?

[cals400ex]

Originally posted by Raptor4439
from 3/4 to full it sputters, I used a brand new plug after I thought I jetted it right.... it feels like after it runs a while it gets worse and worse, it spit and sputters more. could the ignition cause this?


i honestly don't know. i would just borrow a friends ignition and see if that helps. i would try to change the mainjet around a bit. where is your needle clip set at? you can also make sure the mainjet or the two screws holding the needle down didn't come out. i assume you didn't leave the choke on by accident?? clean the carb and all the lines coming off the carb. make sure you don't have an air leak on the boot that mounts the carb to the head and the boot that connects the carb to the air filter.

[Raptor4439]

Originally posted by cals400ex
i honestly don't know. i would just borrow a friends ignition and see if that helps. i would try to change the mainjet around a bit. where is your needle clip set at? you can also make sure the mainjet or the two screws holding the needle down didn't come out. i assume you didn't leave the choke on by accident?? clean the carb and all the lines coming off the carb. make sure you don't have an air leak on the boot that mounts the carb to the head and the boot that connects the carb to the air filter.

I'll just snatch the ignition off of my other 400ex. the needle clip is set at the 3rd position and I know the screws haven't fell out, I just reassembled the carb and it didn't run completely right. All of the lines are clean and there is no leaks coming from the boots, im about to go and change the ignition and see what happens.

[cals400ex]

let us know how that goes.