Dynojet install / need suggestions

[meanyellow03ex]

I have a stock 2003 400ex. I will be adding a HMF slip-on, proflow kit with UNI filter, and a powroll vented lid. I have the dyno jet kit also. I've been doing alot of research and it seems people have their machines jetted all over the map. I've talked to a couple of people and they suggested running bigger keihin jets, but I would like to use this kit as I have it sitting here already. I found a pipe test where they dyno'd a HMF and claimed they needed a 148 dynojet main to get the correct air-fuel ratio. That was with the lid on. I'm going to be switching between the vented lid and lid on depending on how dusty the trails are. Does anyone run a similar set-up that knows a good dynojet size? I live 650 feet above sea level and run in 40-90 degrees temperature. I called dynojet and they said to take the lid off and run a 170 main. That seems too much and I won't run the lid completely off either because of the trails in my area. Any help would be appreciated!!!

[PunkA$$]

I've got the same setup and the 170 main works perfect for me!

[cals400ex]

with the dynojets, i would run a 155 at the very biggest and that is with the lid off. with the lid on, go one size smaller

[Mobile Dyno]

I had a 160 Main in my stock 400 and itran awsome. I'm at 312ft elevation too. I just put a 440 kit in and i now have a170 main. I own a mobile dyno buisness. I did alot of testing. We have an air/fuel module and that corrected the jetting. I have FMF Titanium 4 w/ powerbomb header. I just put a HMF slip-on pipe on my brothers kfx400 w/ twinair filter and started with a dynojet 146 main. WAY to lean with the air/fuel Module. I ended with a 165 main. Air/fuel was perfect on the module. Just an example. I wouldrun 160 w/ the lid on and raise the needle 1 notch. Hope this helps

[meanyellow03ex]

Like I thought, all over answers again. Seems like i'm going to have to jet it too rich to be safe, or take it in so the bike shop can run it on their anaylizer and tune it to perfection.

[PunkA$$]

Like I said I'm running the exact same setup as you (only with a White bros pipe) same elevetion and everything, just try the 170 first and see how you like it. Mine does'nt miss a beat from standstill right to the rev limiter. It's night and day power difference from stock too!

[meanyellow03ex]

I'm not saying a 170 won't work, but might not be optimum either. I don't like how the kit goes from a 146 jet to a 170 depending if the airbox lid is on or off.

[PunkA$$]

I know it seems like too much. But the dynojet sizes are all wacky.

[ewalker302]

I have a pipe and filter no/lid, and a sparks degree key. I tried all the jets and the 146 ran the best for me, the next size in the kit 155 was way too rich. I am running a 148 now, and it runs noticably better than the other sizes (146,150).

Dynojet will sell you the 148,150 pretty cheap. I know it blows that they don't include these sizes in the kit, when they put 2 jets smaller than stock in the kit.

Or you could do what I did, and e-mail DJ and complain.....they sent me 3 jets, and a new holder for free.

Oh and the reccomendations that pipe manufacturers give are always way rich....they dont want somone blaming them for running lean & messing up their engine.

:bandit:

[sandspanker]

dont waist your time with the jet kits . they suck waist of money

[meanyellow03ex]

I will let you all know what is the best dynojet next week. I have an appointment to get it dyno tuned on a climate controlled dynojet chassis dyno next monday. That should put to rest some of the inconsistancy in jet recommendations.

[F-16Guy]

Originally posted by sandspanker
dont waist your time with the jet kits . they suck waist of money
That would be my first answer. Save yourself $40 and just buy the next three larger Kehin jets. If you need more than a Kehin 155 with a slip-on and a filter, you let me know what pipe and filter you got so I can go get 'em! If you have to get the kit, follow the directions for the Stage 1 jetting. You would have to have a full race motor to run a DJ 170. I know, I have the kit and I'm running a 160 with my mods. Depending on altitude, you'll probably end up with a 148, or 146 if you're up in the hills a ways. Get yourself a 40 pilot jet, too. It will make your quad much easier to start.

[t boy]

I HAVE A 400EX WITH A STAGE 2 HOT CAM 11 TO 1 PISTIN :PRO CIRCUIT HEADER AND SLIP ON PIPE . I AM ABOVE SEA LEVEL. I HAVE A DYNO JET KIT .I RUN WITH MY AIR LID OFF. WHAT WOULD BE THE RIGHT JETTING SIZE FOR MY 4_WHEELER.

[jt911]

www.jet4power.com
Jetting will be perfect!

[sam the brave]

i got a 160 main jet in mine and it is stock and it runs perfect a 148 main jet is stock so use the 170

[meanyellow03ex]

Ok everyone. My 400ex was dyno'd today. The results are way off what I was thinking. I had the HMF slip-on, pro-flow air intake kit with foam filter, and a powroll vented airbox lid. I installed the dyno-jet jet kit with a 148 main and clip in 3rd slot, 3 1/2 turns on the mixture screw. The dyno techs said the dyno jet kit was crap and took it out completely because they could not get a steady air/fuel ratio across the rpm band. They then put in a 155 keihin jet and ran it. Air fuel ratio was too lean at 16:1 to 18:1 at higher rpm's. It took a 170 keihin main jet to bring it down between 13:1 and 14:1 air fuel ratio. WOW!!! I guess HMF wasn't off with their jetting recommendations. It also put out 27.3 horsepower at the rear wheels. The dyno tech said that is over 1 horspower more than he's ever seen out of a 400ex with similar mods. So I am happy with the results. I'm glad I had the dyno tuning done as I had it messed up... Good luck to you all with jetting...

[jt911]

You have instant feedback with the jet4power meter installed.
You can use it on multiple motors. Next best thing to having your own dyno.