wonder why they changed from 167.5 to 172.5? i bought a 167.5 today will try it this weekend.

 

Trailrider, According to partsland.com, they represent that both the 400 and 500 share the same pump for 03, I would assume the same for 04 as well, which would mean that its probably not going to be a fuel pump issue. If its big enough to feed the 500, it will surely feed the 400. So Mine is rejetted, I pick it up tomorrow, They dropped the main. I will post after the weeknd to the results as I have a test area that it acted up in every time.. so It should be a quick test.

I also question the Jetting change.

Ron
04 Sportsman 400
Heelclicker
GPS

 

ktmguy,

I am going to ride this weekend too, I have the 167.5 jet and can swap out my friends new pump so we should find out something.

 

phattpat is right, at least for 0 to 3000 ft elevation. put a 162.5 main it and it will run great. We have had several 04.5 Sp400's come in for this problem and that is the fix! We are at sea level here and it works really good, no more bogging and cutting out.

 

may have to give that a try too, thanks for the info.

 

[img]i/expressions/face-icon-small-smile.gif[/img]Had similar problem with my wife's new 2004.5 Spoertsman 400...I installed the DYNO-JET kit and the atv runs much better..We also have a K&N FILTER INSTALLED...

 

Here are the results of todays test: we found a hill, greater than 45 deg. climbed it first twice with no changes. tried swawping out my pump for my friends new pump and seemed to make alittle difference. then tried the 167.5 jet, BIG difference!! changed pumps back and still ran good. my friend already had the 167.5 jet in and with the new pump. Later on in the day with a slow steem climb his did mess up alittile, (he had an adult passenger). mine did it slightly 2 times all day climbing some pretty steep hills. I think the 162.5 jet that has been mentioned in this thread may be the cure. i checked the plug before i changed the jet (after approx 3 miles low range riding) and the ceramic was "brand new" white. checked it again tonignt after approx 15 more miles and its still the same color. do smaller numbers on the jet make it richer or leaner? i assumed leaner. which , by the plug color, i went the wrong way but it helped??? maybe someone can tell me what the numbers mean.

 

The smaller numbers mean less fuel, so you leaned the mixture out. What I'm wondering is, is it more a case of the midrange being too lean than the main jet? The main jet, which you changed, controls mixture from about half throttle to wide open. The slide needle controls mixture from just off idle to about half throttle. By putting in a leaner main jet, you reduce the amount of fuel going past the needle as well, which slightly leans out the midrange as well as WOT. You're probably not climbing hills that steep wide open, which means you're in the midrange, which is controlled by the slide needle in conjunction with the main jet.

It does sound pretty lean to me, the plug shouldn't be white. I'd be tempted to put the 172.5 back in and try lowering the slide needle a notch or two and try it. It's a pain trying to set this stuff up, especially while you're away from a garage and workbench.

With the original jet in place, you said it worked fine except under heavy load, which means it wasn't desperately rich to begin with. The needle adjustment might work, it only makes a minor change to the fuel flow.

 

Chilly,
Thanks for clearing up the jet numbers. before i changed the jet, it climbed ok up to mid throttle. the only time it has ever given trouble is above half throttle. the needle clip was in the lowest setting. the hills we climb usually require full throttle at least part of the climb or you wont make it. i know if i go back to the 172.5 jet i will be right back where i started, maybe i need to richen the lower end somehow. the white plug bothers me but it runs sooo much better than it did.

 

My results are much the same. Im running the 162.5 now as I had the 165 in mine from before.
I took it Over to the same pace, put it in a bind in 4 low and started spining tires as before where it was cutting out.
This time, it didnt cut out.., Lost a few rpms, but didnt cut out. I also picked up about 100 RPMS according to the digital tac.
Where I was Mostly Hitting 45 from point a to point b, Im now hitting 50 (im running the heelclicker clutch kit with the shoulder weights and the white spring, stock tires.) Its DEFINITLEY 100 % better, STILL not 100% sure its right though. as mentioned Above I was already thinking of the Needle, I havent looked at mine yet to see where its currently sitting, but if I have any room, I think Ill drop it a notch and try that.

Trailryder, Keep playing, I will 2, as it seems we live about the same elevation.. so When one of us gets it perfect, it in theory should work for the other.

edited to say: my plug was JET BLACK. Its now a tan/grayish.
ALso, If we cnat lower the needle anymore, then we will have to swap out down a size to see if that changes anything.

Ron
04 Sportsman 400
Heelclicker
GPS