I'm curiouse as to why sledders never really seem to mention air screw turns, pilot jets, and different needels or the needle clip position . On my KTMtalk.com site guys constantly discuss these and make very small changes. I would've thought a sled would require the same kind of tinkering. Especially on a trail sled. what do you guru's have to say?? :thumbsup:

Read thru the posts, man. There is all kinds of talk about carb settings. It's a little tougher to do because of the design of the TM-40's, but it's still being done.

Don't know how others think of this, but to me it's an initial setup thing. Once accomplished, I'd prefer not to have to deal with it again unless a major modification has been installed....and yes, I realize it can sometimes be a little tricky to achieve a good setup that works the way I want across the various temp ranges that I run in.

If I were not on the trails as much as I am, and on a track instead, it would be a completely different matter.

That's one of the things I enjoy most about the sleds I run. The relatively laid back attitude the motors seem to take, all the while developing all the power I've come to expect from them.

Like idooski said their is a ton of posts and very in depth on the ski-doo forum on the subject of main jets, needle jets, jet needles, and pilot jets, although you might have to go back a little ways.

I have made a few 03 440 rev's hook up so hard on the ice that the engine will bog between the 60 and 80 foot mark.
The sled launches out of the hole, hits top rpm then dies with a hollow "baaahh" sound, then back to life again...
Have found that this sled really needs the fuel in the bottom.
We cleaned this up with going from stock 25 to 40 pilots...Putting the needleclip from #2 to #4.
Have gone back to stock settings...same thing..."baaaahh"
Back to loading fuel, and no bog, just increased holeshots....even add slight more flyweight.
I do not know or understand what goes on here and I will not pretend to either. I just know that particular sound in many sleds and then increase pilot size...Improve holeshot and strong engine.

...might not idle the best, if at all though. :D

Dogg, I think the reason the bike guys are so focused on the low end tuning is that's the rpms they do their most riding. With a gearbox you can be a gear high and want it to carburate clean pulling off the corner etc. On our sled alot of this rpm range is pre-clutch engagement so we don't really notice it. Also the cvt clutching on a sled keeps the load on the motor somewhat linear in comparison to a bike that may be in one gear or the other.

Joe, the way I understand it there is always a spot where the pipe isn't working, port overlap has lost charge, trapped compression is low. The charge doesn't light off because it is lean, isn't mixed well, it's not stratified ( I think that's the word). It's a twostroke thing. More fuel cover's it, the downside is it also adds fuel where you don't need it. If you've ridden a DI or SDI motor you'd be impressed how well they run at idle and low mid rpms, fourstroke like. If a bigger pilot works, what the hell! Sometimes a stepped needle does a better job than a straight on two smokers for this effect.

that depends what range your having problems with. my rule of thumb is idle to 1/4 is pilot, 1/4 to3/4 is needle, and 3/4 to full is main. is this still correct.

Dynamo, the need for fuel that you discovered is a issue that plagues lots of racers, mostly those who are inexperienced... On grass in the summer running larger pilots its a MUST... Its amazing that a sled tuned to run in 10degF temps needs MORE fuel in the low speed circuits to race when the temp is 70 degrees F.. Thats why I dont get into much detail about this stuff.. no 2 sleds have the same needs, too many variables..