Do I have to rejet for just a slip on pipe?

[04 YeLlOw 400eX]

I know it's a stupid question but.....
Do you have to rejet for just a slip on pipe?

[honda400ex2003]

its recommended, 150 main, 3.5 turns out on the f/a screw and you should be good to go.

steve

[dxcody]

Originally posted by honda400ex2003
its recommended, 150 main, 3.5 turns out on the f/a screw and you should be good to go.

steve


Bingo.

Take off the lid for a little more HP while your rejetting

[Drfat400ex]

I'd go 152 if you also have a filter, then you don't have to turn the a/f screw out quite so far and risk it falling out.

[honda400ex2003]

theres absolutely no relation between a main jet and the f/a screw.

a 40 or 42 pilot would not require much change in the pilot screw.

if he is running with his lid open he will want a 152. he will be fine with a 150 running the lid on, a filter, and a slip on.

stock filter and lid off would also be fine with a 150.

steve

[Drfat400ex]

Yeah I had a bit of a, non-thinking moment there haha. But yeah upgrade your pilot I wouldn't want to turn the a/f screw out quite so far, my buddy has a slip on and a k&n and the 152 worked perfect for him, but every machine is different, I'd start at 155 and work down.

[JOHNDOE83]

Some slip ons come with jetting, all aftermarket exhausts say to use a 155 main jet.

All quads are diiferent, 155 is a baseline, It should be anywhere from 152-165 just for a slipon depending on your atv.

[04 YeLlOw 400eX]

Is there a risk blowing it up if I don't rejet?

[b0rn c0nfused]

Originally posted by 04 YeLlOw 400eX
Is there a risk blowing it up if I don't rejet?
I don't know about blowing it up but it will make it run hotter running it lean. It will rob you of power to.

[dxcody]

Originally posted by 04 YeLlOw 400eX
Is there a risk blowing it up if I don't rejet?

kinda... they "say" it can burn up your piston if you dont rejet because just like Born said, it will run lean.

Trust me, i burn up a motor before. Not fun!

[russellsroost31]

id have to say 160 main jea with a lil over 1/4th turn out on the mix screw will give best results but u got to run open air box on this set up i run it for mx

[honda400guy]

Originally posted by honda400ex2003
its recommended, 150 main, 3.5 turns out on the f/a screw and you should be good to go.

steve

i had to go up to a 160 for my big gun evo:D

[04 YeLlOw 400eX]

My buddy got a motorworks SR4 slip on, which I'm gonna get. He ran his without jetting for about a year. He said it ran fine.

[quadmanw]

I did the same with the motoworks ran fine for over a year

[atvrider13]

The 400ex in stock form is on the lean side. And thats with a 148 main jet. A 150 wont do much. Go with at least a 160-165ish. And for you guys that say: Hey dude i put a pipe on and aint ever rejetted it and it runs fine. It mite run fine yes but run for long probably not. With running stock jetting with a pipe you will be running too lean and just because "it runs fine" that doesnt mean you arent doing damage to it. Over time by running your atv lean it will lead to premature engine failure , typical 400ex topend redo : $250 . Rejetting only takes about 5-10 minutes and costs $5 for a jet. Do your quad a favor and just rejet the damn thing...

[dxcody]

^^^ Very well put.

I think that running lean actually makes MORE power, BUT as stated before, lean is the WORST condition a quad can run.

Me and almost every other member of this site prefers to run a little rich. Not bad, but a little rich.