Cals...and other jetting info ppl.

[new03400]

i have a 2003 400ex, and its stock. i recently purchased an HMF slip-on, k&n filter and outer wear, ground header welds, and modified the air box snorkle tube.

im about 300-350 feet above sea level. i want the most power from those mods and jetting, and a little lean or rich, just whatever gives me the most power, it doesnt matter i got the 5-year warranty!

and would removing the choke be worth the time?

thanks for your time,
steve

[AtvMxRider]

Originally posted by new03400
it doesnt matter i got the 5-year warranty!





Your warrenty is null and void when you made the 1st modification;)

[LazeR]

42 pilot, 2½ turns out, MJ at like a 155, try from there :p

dont really have to do the pilot but it helps out in starting

[meanyellow03ex]

I've got a 170 keihin in mine. The 155 was too lean on the top end. I had mine dyno tuned and the graphs between the 155 and 170 were close power wise but way different air/fuel ratio wise. I probably wouldn't have noticed anything funny with the 155 by seat of pants driving. Everyone tells me I'm too rich but the air/fuel graph shows otherwise and it runs great. Hmf's recommendations are like a 165-170 with a slip on and seem close to me.

[new03400]

about the warranty...its good for whatever external mods that i do including rejetting!

im in like sin with the owners of the local honda shop!

steve

[sampleez]

what's the deal with grinding the welds on the header

[44oEX]

it gives better flow

[hondarider2006]

Originally posted by sampleez
what's the deal with grinding the welds on the header

lets your motor breat better, kinda like a cheap-o aftermarket header, just not as good but better than stock:p I grinded mine down...didn't really notice a difference, but it didn't hurt anything.

[meanyellow03ex]

I thought I read somewhere that the exhaust port on the 400ex's cylinder head is smaller than the welded part of the header so really there is no gain from it. Mainly psychological probably..

[44oEX]

I don't know about that but even if it is the exhaust gas still goes in the little cup at the end of the pipe and expands then it goes tru the weld so it will create turbulance. if the cup is the same size as the pipe and there is no weld in the way there will be alot less turbulance in the gas.

[nosliw]

Originally posted by AtvMxRider
Your warrenty is null and void when you made the 1st modification;)

nu-uh :p

[cals400ex]

you will get more top speed out of a keihin 155 than a 170 for example. i have tried them both. like meanyellow said, he has dyno graphs. i just wouldn't go that large. i have seen some dyno's say you need a 170 and others say you need much smaller. i am not sure what the difference is from. i can tell you if your interested in power in the upper gears, your bike will be faster with the 155 in. you shouldn't see much of a difference in the lower gears between the 155 and 170. good luck

[44oEX]

a 155 will not be any faster then a 170. it can be but it all depends on your setup altitude temp ....

I you have to run a 170 cause the 155 is to lean then the 170 will be faster. But if the 170 is way to rich then use the 155. or something in the middle and that will be the fastest setup.

The fastest one is the one that is jetted correctly. not lean or rich

[meanyellow03ex]

even with the 170 jet, between 6000-9000 rpm the bike was around 14-1 air fuel ratio. I wouldn't want it any higher than that for engine safety sakes. With the 155 it was around 17-1. Too lean . Especially for an air cooled motor. I'd rather be a tad rich than lean. And for the 5 year warranty, who cares. If you run your bike too lean to exract that extra .3 horsepower, you'll lose more power from cylinder, ring, valve damage than you gained to begin with. Run it where it should be and be done with it.

[hondaex03]

I have about the same mods minus the header weld grinds and I removed the air box lid. I got the Dyno jet kit and it said to use thier 170 main jet and I am at 950 ft.

[cals400ex]

see, everyone has their own opinion. i can guarantee you it will be faster in the upper gears with the 155 in given your at elevation of 400ft in normal temps. yes, humidity plays a role too. i only run a 160 in my 426. sparks told me to run: keihin 158 and 45 pilot jet with cam, piston, high flow air filter, no air box lid, and sparks X-6 pipe at sea level elevation, and 70 degree temps.

[44oEX]

just put in a 155 and see what it does. if your to lean ( plug reading) go to a 160 and so on.

[nakomis0]

All bikes are different, to bikes off the same line from the same day can have different jetting needs. Small shaps here and there on the ports, a larger weld here or there on the exhaust, amount of oil on the filter..... when theres other things like altitude, humidity, gas.. ect, ect,. So any number anyone gives you is just a guess.

And that guess will get you in the ball park. I ran a 182 in my slightly modded 400ex and so many know it alls said 'thats to big, go to a 170' or whatever. but it was tuned by a dyno, and I dont care if your Mickey freakin' Dunlop i'd still believe the dyno.

[new03400]

cals...
what about the piolet jet, what should i do there? should i remove the choke or is it not worth the time and hassle?

thanks again,
steve

[44oEX]

well do you get any winter. like cold weather and snow and stuff. if so you sould leave the choke you will need it. and you could change to a 42 pilot for easier starting. but If it stays warm year round then you can remove the choke and stay with a 38 pilot

[cals400ex]

i would honestly go up on the pilot jet for easier starting. i can run a 42 or 45 pilot year-round with no problems. i just need to tinker with the fuel screw here and there. if your set in stone and not changing the pilot jet i would at least turn the fuel screw out a bit.

[new03400]

what about the choke? leave it in or take it out?

steve

[44oEX]

Originally posted by new03400
what about the choke? leave it in or take it out?

steve


Originally posted by 44oEX
well do you get any winter. like cold weather and snow and stuff. if so you sould leave the choke you will need it. and you could change to a 42 pilot for easier starting. but If it stays warm year round then you can remove the choke and stay with a 38 pilot

[new03400]

sorry 440...

i completely over read that, yeah it does get pretty cold in the winter...so im gonna go off of what you said and leave it in.

thanks for your time,
steve