ported head, jetting changed quite a bit

[cals400ex]

i was just wondering if most people noticed their jetting changing quite a lot after a port job? my plug is much much darker after i got an aggressive port job. it seems like it is several sizes richer. i was just wondering if most others noticed this or if maybe if the port job wasn't the highest quality?

[MIKE400EX]

If the jetting went "richer", that means the carb is seeing a stronger signal. That is a GOOD sign, the engine is pulling in more air (because of the porting). Now as long as that is happening in the RPM range you mostly ride, you should be see a noticeable improvement (after you get the jetting corrected of course).

[cals400ex]

i am currently running a keihin 158 main jet on my 426. i guess i will go down to a 155 and see how that works. i don't want to go much smaller than that. the plug is definatly tan. i normally run it leaner than this. i just need to get this stock carb off and get the fcr 40 on and see if it works better with this ported head.

[MIKE400EX]

That's a good idea!

[mbiigambler]

Hey CAL,

I have a fcr 39mm, I'll sell you!:D

What do you have for your airbox setup?

Get that motor more air and fuel.

[cals400ex]

Originally posted by mbiigambler
Hey CAL,

I have a fcr 39mm, I'll sell you!:D

What do you have for your airbox setup?

Get that motor more air and fuel.

hey whats going on? i haven't talked to you for a long time. i have the head on and it seems to be doing great. i do need to get my fcr 40mm on and try it out. i am just trying to get the adaptors to fit right. the head seems to pull a little longer at high rpms, even with the stock carb. not much different but i definatly dont think it hurt. my jetting just changed a ton. i was pretty shocked. i am just a fan of not overkilling the jetting. i get much better results running the smaller jets. i am currently beating my buddies 416 without any problems, and he is running a FCR. i am getting my flywheel lightened now and we will see if that makes a difference or not. i run my air box lid on. i know many will argue with that but i have excellent results with the lid on. both my buddy and i run it on. we have done testing and testing and we both find we like how both of our bikes run with the lid on. we noticed that the jetting will change from 1-2 mainjets sizes easily with the lid off, but we don't get better power. many think the power is better because of the extra vibration and noise. this does come down to physics, which many don't understand or even take into consideration. the volume isn't all that matters, velocity is very important though. the larger opening you have, the more volume but less velocity you get. a smaller hole will provide much better velocity. i am going to buy a gt thunder velocity stack and put it in the lid. this should help things out a bit. who knows, i may even need to plug up my snorkel for best results, and then again maybe not. i am willing to try any jetting and air box setups. between my buddy and i we have tried K&N, UNI, Twin Air, and stock filters. i have tried those uni air vents, outerwear air box covers, no air box lid, and the lid on. in my jetting box, i currently have 19 keihin mainjets, so i am willing to try about anything. i have had the best results with the smaller mainjets and the lid on. i would love to drag race others with similar mods just to get a comparison. however, i don't get the chance very often besides my buddy. thanks for the offer on the fcr. however, i do have a 40mm fcr laying here than needs to be put on the bike. i will probably do that over christmas break. i guess it is worth noting i am at 625 feet above sea level and the temperature is about 50 degrees now. i am up for any suggestions. nice hearing from you.

[torqen2k1]

Wow :eek: thats a smal main jet size. I just had my head ported and polished with a 3angle valve job. 426 weisco. and im jetted at 180 main. But you have to remeber thats its alot colder and the air is alot densir too.and I have a 2004 400ex and yes it has a 38mm carb stock.

[cals400ex]

we will have to go riding sometime. we will have a battle of the "which size jets to use." i bet my 426 is faster. :macho

hey, i am just playing with you. yeah, i read that the larger bore engines my require smaller jets sometimes. i think the carb may be getting a better response and it may even be possible for more fuel to be pulled through the same size jet. it is kind of like more suction in a way. the harder you suck through a straw, the more liquid comes through. chad said he can run a keihin 155 main jet through his 500 stroker. :eek2:

[mbiigambler]

What's your buddy have for gearing? I find it hard to believe you can beat your buddy if you're quads are setup close and he has the fcr. The fcr just wakes the motor up!

I'm willing to bet your buddy needs to make his gearing taller.

As much as you like working on your quad, you need a cannondale!

[cals400ex]

Originally posted by mbiigambler
What's your buddy have for gearing? I find it hard to believe you can beat your buddy if you're quads are setup close and he has the fcr. The fcr just wakes the motor up!

I'm willing to bet your buddy needs to make his gearing taller.

As much as you like working on your quad, you need a cannondale!

yes, it seems i am always tweaking my bike. however, i don't want crap to break. i don't like fixing stuff, i like modifying it. :)
my buddy and i both run stock gearing with 20 inch rear tires. the fcr's really wake up the throttle response. i didn't get a huge gain when drag racing though. i realize it did help but not like adding my cam and piston did. i am running a 11:1 thermally coated 426 and my buddy is running a 10.8:1 416. i am running a sparks x-6 and he runs a sparks x-4. he runs a stage 2 hotcam while i run a TC mx grind cam. in a drag race i am probably 3 bikes in front of him by the time we are in the middle of 5th gear. i know many may say his pipe is slowing him down. that thing really helped a ton when he put it on. the weird thing about it is, he has me top end end. he almost always has. it seems that his pipe has more back pressure (which it won't rev as high as mine) but in the upper gears it runs strong. it feels like my x-6 is too much pipe for my motor. my bike has always ran really strong with more power in the 1-3 at upper rpms. then if feels like my pipe doesn't have enough back pressure. by the way, he has me top end when we both run the stock carbs. well, when he has the fcr on, he has me up top too. the only other thing i can think of is my rear tires. my buddy run 20 inch holeshot XC's and i run 20 inch shredders. well i don't think my tires were ever correct when i bought them. one i have to run 8 psi in and the other i need to keep at 4psi. this shows they are not made equally. i am wondering if this slight difference may affect the small top speed difference between our two bikes. as you can see, all this crap runs through my head and i am constantly trying to get an edge. it is worth noting that my bike is much much slower with a 36 rear sprocket on. 4th and 5th gears are absolute terds. once again, i think this is from my x-6, but i could be wrong. it feels like i need more backpressure and the bike can't pull it in the upper gears. neither of my buddies bikes do this. :huh then again, i am the only one running a x-6. one is running the x-4 and the other runs a complete HMF. neither of these rev as high as my x-6 does though. however, my motor can't rev as high as the pipe wants to go. i guess i rambled on enough in this post for now. :D

[torqen2k1]

Originally posted by cals400ex
we will have to go riding sometime. we will have a battle of the "which size jets to use." i bet my 426 is faster. :macho

hey, i am just playing with you. yeah, i read that the larger bore engines my require smaller jets sometimes. i think the carb may be getting a better response and it may even be possible for more fuel to be pulled through the same size jet. it is kind of like more suction in a way. the harder you suck through a straw, the more liquid comes through. chad said he can run a keihin 155 main jet through his 500 stroker. :eek2:

Hey Cal well after the winter we should meet up and go up to Silver Lake or BadLands.

[cals400ex]

Originally posted by torqen2k1
Hey Cal well after the winter we should meet up and go up to Silver Lake or BadLands.


that sounds good. i have never been to either place. i prefer the places with good land, not a bunch of mud. i think i am heading to flat river tomorrow. after winter we can get together and go on a trip.

[torqen2k1]

Originally posted by cals400ex
that sounds good. i have never been to either place. i prefer the places with good land, not a bunch of mud. i think i am heading to flat river tomorrow. after winter we can get together and go on a trip.

Well I am goin to BadLands this Saturday or Sunday depending on the weather. I like BadLands because its a very big place and their is trails that have some mud and lots of trails that are dry mud. I dont like to go ridin when their is to much mud. I try to keep my quad very clean. Also were is flat river? Im about 20mins away from Chicago.

[cals400ex]

Originally posted by torqen2k1
Well I am goin to BadLands this Saturday or Sunday depending on the weather. I like BadLands because its a very big place and their is trails that have some mud and lots of trails that are dry mud. I dont like to go ridin when their is to much mud. I try to keep my quad very clean. Also were is flat river? Im about 20mins away from Chicago.


it is actually called st joe park actually, my buddies call it flat river. it is in missouri. it would be too far of a drive for you. i am several hours south of you and this place is south of where i live.

[torqen2k1]

Originally posted by cals400ex
it is actually called st joe park actually, my buddies call it flat river. it is in missouri. it would be too far of a drive for you. i am several hours south of you and this place is south of where i live.

Thats cool. Do they take Db tests of your exhaust their? my next door neighbor has a weekend house that we ride at by Danville. Just out of curiosity how far are you from Danville?

[chad502ex]

Originally posted by cals400ex
chad said he can run a keihin 155 main jet through his 500 stroker. :eek2:

true, I run a 155 thru my 502 when I'm not running my Lectron. Lectrons use a metering rod.

chad502ex.com

[cals400ex]

Originally posted by torqen2k1
Thats cool. Do they take Db tests of your exhaust their? my next door neighbor has a weekend house that we ride at by Danville. Just out of curiosity how far are you from Danville?

no, they do not check for anything. i honestly don't know where danville is at??

[cals400ex]

Originally posted by chad502ex
true, I run a 155 thru my 502 when I'm not running my Lectron. Lectrons use a metering rod.

chad502ex.com


i am running a 155 now. it seems to run great. i just need to get my fcr40 on. it is just tough to get the adaptors and everything hooked up to work on a 400ex. i wouldn't mind running a lectron but i don't want a ton of maintenance