Hey Everybody, Ill try to keep this as short and sweet as possible.

After not riding for almost 2 years due to school and other expenses taking up all my time and money, I am finally getting back into riding.

I have a 2003 Ltz 400 with a k&n air filter, yoshimura slip on exhaust, jetted ( i dont remember what jets i switched to) and the last mod i made right before i quit riding was adding an athena 440 kit. Really only was able to ride it enough to break it in after getting the kit on before me and riding went our seperate ways.

Well this weekend, I went through and changed the oil, cleaned out the air filter and put in some gas and took it out for a spin and

I have a couple of question.
First off the problems.
It is very cold blooded right now for some reason. It doesnt want to start and the only way to have it idle is to have the choke all the way on. Once i take it out for a spin it gets better but it still wont just sit there and idle. Also, it tends to backfire a lot. When im on the gas opening it up and then let off and use the gears to slow down it back fires like crazy, and it also backfires whenever i hit the gas while its idoling.

So my questions are, what could be causing it to do this. The jets were set up for when it was a 400, do i need to rejet with the 440, if so what jets do i need, or do i need a bigger carb. Do i need to adjust my air/fuel mixture screw?

Secondly, What changes could i make to get even more power out of the big bore. Would i notice a difference by chaning out the cams, can i change out the cams myself? What cams do you reccomend?

Im really excited to be back to the sport, I have missed it alot. Any help would be greatly appreciated! Atv connection forums never failed me back then so im sure this is the place to go.

 

hey welcome to the forum!

you should definatley re-jet (richer) for the increase in displacement. that should solve your problem.

and for the cams, usually when people go as far as a 440 kit they also throw in some performance cams. they probably wouldn't hurt.

good luck!

 

Thanks!

Yeah I was thinking that i had to be running lean. Does anyone know where a good place to start would be as far as jetting is concerned with the mods i listend. Also, exactly how to i adjust richer? which way do i move the clip on the needle, do i go to a larger or smaller jet? do i need to change the pilot jet as well?


And as far as the cams i was looking at hot cams and webcams, is there really much of a difference between the two? if so, which is better

 

hmm well for the main jet, do you know what # youre running now?

and for the needle, i'd move the clip down a notch or two, thus raising the needle.

the pilot jet probably wont need to be messed with. however there should be a screw that allows for a little tweaking of the pilot circuit...

i dont know too much about hotcams, other than they are definatley well established and ALOT of guys run them in thier z's.

in my past expirience with webcams, ive found that they offer MANY different grinds for the same motor, and most arent even on thier website. you gotta call them to see whats really available.

with that said, what kind of powerband are you looking for? low-end for the woods, or topend for mx? or maybe something in between?

 

im not sure what jet size im running right now, if i pull the carb apart will it say on the jet what size it is?

as far as power band goes, I mainly ride in the dunes, but with a little trail riding here and there. So i guess id want a good strong mid and high range but without sacrificing too much of that low range power id want when i do hit the trails. wouldnt mind a good power band for drag racing in the dunes either.

 

the # should be stamped on the jet, so when you take it apart you should be able to figure out where to go next. i'd go 3 or 4 steps up in size...

for the cam, i'd give webcams a call and see what they reccomend...

good luck!