Need someone who knows their jetting

[kx254]

K guys tell me if this is right?
I have a FMF Powercore 4, choke taken out, 42 pilot jet, and 155 main jet, needle is at stock setting, the temp is usally between 0 degrees celcius(32 f) and 20 degrees celcius(68 f), and a riding altitude of anywhere between sea level and 250 ft.

I did have all this, but still had the choke and had a 148 main jet, and it ran perfect, I removed the choke, and it was definantly getting too much air, so I added the 155, but it still backfires a bit, but not as much as with the 148.

What can I do to make this perfect.maybe a bigger main again, or a needle move, any suggestions?

400 ex

[Leo]

Originally posted by kx254
but it still backfires a bit

When does it backfire..?

Leo

[barbwire44]

Hey I had this same set-up at one time here is what you need to do, Pull the carb add a 158 main go down to 40 pilot jet and raise that needle! Move the E-clip one position below stock. the air screw should be within a 1/4 of turn of the stock position. The needle is what is causing youre backfire. I think at one time you said it ran fine on top? -correct. The pilot sounds a little to big. I can see maybe a 42 but not a 45 thats overkill. Raise that needle up (lower the clip) And I bet the problem disappears.

[kx254]

backfires when I am at high speed and slow down with the clutch out, it also became harder to start(used to be perfect before I removed the choke). Ialso tried to remove the airbox lid but I would need hugh jets for that because that made it completely bog out.

[kx254]

raise the needle how many notches?

[Red Rooster]

He said to move the clip down (twoards the pointed end) one notch.

[barbwire44]

Well if you removed the choke it is harder to start but to remedy that, before you hit the start button push the throttle wide open three times and then hit the button. The big pilot may be causing the start problems youre probably getting a bunch of fuel and not enough air to compensate. Go down a size or two on that pilot most likely a 40. and raise that needle to raise the needle you have to move the e-clip down one position it should be the fourth slot from the top. If you don't know how to raise the needle send me a pm I should be able to explain it.

[440exnacsracer]

hey, barbwire, what jets do you use on your 440ex?

[barbwire44]

I run my K&N Filter and a 170 main but when it gets dusty and dry I use a uni filter and a 165 main the pilot is a 42, the needle is one clip below stock I'm thinking the fourth notch down and I am pretty much a 1/4 of a turn out from stock on the air screw. I like the performance of the K&N but I do not like to run it when it gets hot and dusty because it just doesn't catch the fine stuff. The uni is definately a better for the engine filter but a little more restrictive I can tell that just by the jetting. If I have my 170 main and the K&N on and switch to the uni I will run rich and usually foul a plug within an hour.

[440exnacsracer]

k, thanks. i just bought a 440 kit and have a kandn and have holes in my airbox, so im guessing my jets should be in the 160-165 range would this be correct? thanks
Ben

[barbwire44]

I would throw a 170 main in and see what happens if she don't sputter or bog I would go bigger. Those airbox holes add a bigger volume of air. I can't have holes because of the riding conditions. I would definately drop a notch on the needle also. Let me know how that hot cam works out I have been kicking around that idea myself.

[R-Crazy]

tell me if this sounds right,
i used to have these modds, pipe, k&n, and for that i moved the clip on the needle down 2 postions and it ran great. now i put 7 holes in my air box, 6 w/ vents, and i put a 130 jet in (stock 122). is this about right?

dave

[440exnacsracer]

hey, barbwire, i tried to pm you, your mailbox is full though. the hotcams wont be in stock till the end of this month and im getting my motor work done right now, so i might wait till the end of the summer to put one in, of course it would only take an hour or so. oh, the holes in my airbox have those small filters in them. you can get them from dennis kirk. they keep some dirt and debris out, you should get some.thanks for the advice! later
Ben