[cgrady88]

Just recently put curtis sparks exhaust on my 07 400 ex. It has a 168 main and a 42 pilot and my needle valve was not adjustable. I took a needle valve out of another 400 that was adjustable and it is on the 3rd notch. Fuel/mix is 3 1/2 out and now it is really really cold natured. I have to choke it and let it run a while while i give it a little gas. When i warms up its fine. Before when a had the hmf slipon with the 42 pilot never had to use thew choke at all. Was thinking bout taking the choke off but I would never get it cranked then. What is my problem or is this normal when I go to full exhaust? Why wasnt my needle valve adjustable(no way to move the groove on a 07)?

 

[Redracer]

You are getting WAY too much air or not enough fuel, however you want to look at it. With a full system I'm pretty sure you should be up around a 180. 168 seems small.

 

[cgrady88]

on the sparks web cite they call for a 155 main, 45 pilot stock needle placement and 2 turns out. It just dont sound enough huh.....should i go up to a 175 or 180 and keep the 42 pilot or replace with 45 pilot?

 

[Redracer]

Everyone I know with a 400EX is in the 175-190 range with a 42 pilot

 

[DAN400ex]

Everyone I know with a 400EX is in the 175-190 range with a 42 pilot

I'm with red, if you have a full exhaust system and any kind of air intake system you should be running a 170-180 main jet. I have a 170 main with a powerlid and a slip on exhaust.

 

[TRX2fiveO]

Full exhaust I agree goto www.rockmountainatv.com and just order the kehinhex jets in the sizes you need they are much cheaper there. I never use my choke on my250X I have a 400 carb on it. I pump the throttle about 4 or 5 times and just barely hold it down and it starts every time. I would say you're going to be around a 185 on the main put the stock needle back in the taper is different on the adjustable

 

[cgrady88]

thanks guys...think im gonna get 170 to 185 jets and put my original needle valve in cause like yall said it should not be hard to start. It will probably help my performance also

 

[TRX2fiveO]

good luck and keep us posted.

 

[cgrady88]

went with a 180 took air box lid off and runs good...good color of spark plug....still hard to start...any suggestions?how bout if i go to a 45 pilot

 

[TRX2fiveO]

yeah bump up the pilot to a 45

 

[njrextreme]

Turn your air screw in, start it, back it out until it runs the smoothest, then adjust the idle screw to a comfortable rpm. You cant go by the web site on the air screw. It will run diff on a hot dry day vs. a cool damp day. If your in cold winter temps, they become real hard to warm up if your set up for summer. Best of luck, welcome to tuning.
Nick

 

[cgrady88]

decided to adjust idle screw...damn that a b*tch...finally a had to take the carb off...I adjust to 2 1/2 out cranks fine(4 pumps of the gas no choke) but still got that air sucking sound sometimes. Have not run it to see if there is any more probs(10:00 at night neighbors would not like it).Any sugg. bout gettn to the idle scew?How bout the air sucking noise?Will keep u posted

 

[Redracer]

When your airbox lid is off it will create a sucking noise...

 

[TRX2fiveO]

Agree^^^^^^ put the lid on and it will go away

 

[cgrady88]

still hard to crank but better..Should a screw idle screw in or out(im at 2 1/2 out right now)...When it is warm when a I rev up still cracking and poppping...Did I go to much with the man jet(180)? I noticed when got rev put through gears cuts out i little at the top of rpm range???? too much air with lid off?

 

[njrextreme]

Do a plug check and let us know how it looks.

 

[cgrady88]

NOT GOOD...Was riding along and lost power small puff of white smoke and would not start back. Got home and pull ed the plug and put my finger on the hole and turned over some compression but not alot(should blow my finger off right)I think i blew it up> When turning over small ampunt of white smoke and a little bit of oil blow back on my finger but like I said just lost power no noise or nothing. Hole in the piston? burnt valve ? what is my best case rings?What do u think happened?