!!!Help!!! Jetting on 416ex !!!Help!!!

[tsargent4]

I have a 2003 400ex with a fresh build on it that includes: JE 10.8:1 (416cc) piston kit, Hotcam stg 2 race cam, Uni air filter w/ lid on, FMF Powerbomb header and Powercore 4 slip on. I live in southern (Bedford) Indiana and as of right now I am running my carb with a 165 Main, 40 pilot, and needle on 3rd slot. I have done trial and error continuously and can still not getting my jetting right. I have tried running a spark plug that is a step hotter and I do run 50/50 fuel (110 race fuel and 94 octane). Once the motor gets good and hot and I let it sit and idle for about 15 seconds it wants to idle down and die(It's not in the idle screw though, I am thinking I need a bigger pilot jet). Also when climbing a fairly big hill in 2nd gear it wants to lose momentum to the point I have to go wide open throttle to get up the hill, but it still struggles. My question is this, what jetting should I have? or try? do I need to get a DynoJet kit or FMF Power up kit? It is to the point I can't ride because I don't want to blow a fresh build just because the wrong jets were used. Any suggestions or help would be appreciated. I am looking for an answer from someone who KNOWS what they're talking about, not stupid answers. Thanks.

[gojk]

For the idle problem, have you tried just adjusting the idle? Could be wrong pilot, but you should be able to adjust it at least close with just the air screw.

Also, when it starts lugging up the hill, how steep is the hill(possibly fuel dumping out of the overflow)not likely the prob since you say that full throttle works just fine. Try dropping the needle one notch.

Does it hesitate or bog if you go from stab the gas at idle?

[tsargent4]

It's a pretty steep hill...but yeah it does kinda hesitate and bog if i give it WOT from idle...

[gojk]

First make sure the air filter is clean, and if you are using a pre-filter on a k and n make sure that is clean. With that done, and I am sure that was the first thing you checked, then I would drop the needle one notch, so move the clip up one position and see how it does.

[tsargent4]

I am running a Uni filter, not K&N, those are junk!!!!...dust eaters if you will....why would I move the clip up, that'd only make it leaner...

[gojk]

Originally posted by tsargent4
I am running a Uni filter, not K&N, those are junk!!!!...dust eaters if you will....why would I move the clip up, that'd only make it leaner...

Yes, try and lean out the needle just a hair. Should get rid of the stumble.

[tsargent4]

ill have to try it this weekend, i am pretty busy with some police training right now...ill try it and let you know how it works...you ever used a Moose Racing power up kit, or FMF power up kit?...or Dynojet?...anyone else have experience with them and how good they are?...

[gojk]

Originally posted by tsargent4
ill have to try it this weekend, i am pretty busy with some police training right now...ill try it and let you know how it works...you ever used a Moose Racing power up kit, or FMF power up kit?...or Dynojet?...anyone else have experience with them and how good they are?...

The power up kits are a waste of money in my mind. Just go and buy the jets you need. I bought the dynojet kit and ended up just going back to stock components because it was hard to translate DJ numbers compared to standard Kehin numbers for a starting baseline. Plus the DJ jets didn't go as big as I was needing at the time.

[xtullyx16]

http://www.atvriders.com/articles/jetting.html

seems me to like u could use that

[gojk]

Originally posted by xtullyx16
http://www.atvriders.com/articles/jetting.html

seems me to like u could use that

That is a good guide to learn concepts, but really jetting is more of a trial and error thing.

[BigLuke]

My 400 done the same thing after I installed my Hot Cam stage 2 K&N and Yoshi, I pulled the baffle out of the pipe and took the lid off the air box and that fixed it. Mine would stumble and wouldnt idle after warmed up, Im running 165 FMF dyno jet, clip on the 3rd notch and idle screw 2 1/4 turns out. Runs fine now, I dont even have to choke it, 2 hits of the throttle and it fires up.

[Thumpin]

I had a 416EX machined by C&D Racing, with a Ross 10.8:1 Piston, ported & polished head, hot cam stg.2, compression is 11-1 with milled head and XR gaskets. Ported stock head pipe with white brothers E series slip on. Running VP110 race with 50% pump gas in a stock carb with choke remove, my jetting was right on the money with 42 pilot, 2 1/2 fuel screw, 4th slot down on needle and 170main jet. Ran very good and smooth, lots of tork!

Than my needs for more top end pull was met by going to a CT Racing midrange full exhaust with their titanium needle at 4th clip down, 40 pilot, 1 1/2 fuel screw, 168 main. The titanium needle made the fuel curve richer, so smaller pilot and main jets were needed to jet correctly. It runs well with the 450's now. My elevation is 2,000-1,500ft where I ride.

Try to find a pilot 40-42 that runs smooth with 1 1/4- 3 1/2 fuel screw turns. I'd run that needle 4th slot down and a 165-168 main jet on a stock carb with lid off. I bet your darn close.

[400ex28]

I ran the same setup but with the lid off and a TC exhaust and ran a 40 pilot and a 155 main and never messed with the needle, ran great.

[tsargent4]

I have yet to stop and pick up a 42 pilot, I'll run and get one asap...but I dont have the port and polish so I'll probably just run a 165 main and move the needle to the 4th clip and use the 42 pilot and see how that works...right now I am having trouble with the new EBC dirt racer clutch wanting to get hot and swell with the 50/50 gas I am running using 94 oct. and 110 race fuel...so I'll try rejetting and let you know how it goes once I try it out...