just got a FMF pipe - K&N Filter
about to replace the jets main to 150.. pilot to 40... original is 148 and 38.. according to Honda.
I tried it already without the jets and it 'putters' at or near red line alot. like either the rev limiter is kicking in sooner or needs gas? I cant tell.

I keep hearing that you can damage engine if your run lean.. is that right? why? Lean meaning - engine needs more gas flow?

anyone out there have the FMF-4 pipe on the 400 - anything good or bad. Its loud - but i cant tell the difference in power yet - maybe its because ive only rode the thing 4 times - and i was just getting used to the 'bunches' of HP compared to my old 300ex...

will jetting make a big difference - even if i only go 2 or 1 sizes up.. seems like a lot of work. I hope its worth it.

Im wondering if i should get a foam UNI or put the stock one back in -since i hear that the K&N is too 'open' I ride 80 percent in sand (Glamis/Gordons) and the other 20 in Baja - dusty trails...??

suggestions welcome ! Thanks Everyone.

 

WE tryed the same thing just to see how it would run with just the exaust.

And it did the same thing.No increase on the bottom, Mid was the same,And it starved and poped on top.

A- Unlike a two stoke, You can not burn down a four stroke. It may run like crap, Foul a plug or not even start. But it will not burn down. If you think I'm wrong, Show me one that has.

B-Jetting will make all the difference in the world period..........And it is well worth it.And yes it is some work the first time. But the payoff may be as high as %30 more power.

c- The bigest thing to learn about jetting theory is the more you can get out the more mix you can stuff in! LET IT FLOW.And do it across the entire power ban.

D- You are quickly reaching the point where more air is needed, Than the factory snorkle can alow in.Jetting to match that pipe will require a proped open air box or holes in the lid to reach full potential.

E-If your in the dust I would stay with a foam filter,But come this time of year you could swap to a K/N.Good luck.

PS.Roost King is right some of these pipes are down right offencely loud! Mine included. But the power Whoooooo!

 

Im about to attempt it today.. i figure Id go 2 over on both main and idle... and see what happens
that puts it on 150 main and 40 on idle.

did you have the FMF4 pipe too? what setting s did you end up with?

 

Oh yea, whats a stage 1,2,3 ..

 

From Dynojet.com

Posted by: John Walls Sunday, March 21, 1999
I will own my new 400EX at the end of this month. I want to put a K&N filter in the original airbox. I will probably run a FMF muffler, but keep the original head pipes coming out of the cylinder. Is this considered a stage 2, and does the 400EX Jet Kit have the specific settings for this type of setup? I just wanted to know the specifics before I purchased a kit.

Also, how does a shade-tree mechanic like me test the new jet settings once I install the kit? I don't have access to a dyno or anything fancy like that.

Reply by: John Marcella Monday, March 22, 1999
The Dynojet jet kit for the 400EX is part number Q107, and has complete instructions for both Stage 1 or Stage 2 whether you have a stock or an aftermarket exhaust. The instructions also give you needle position, and how many turns out your mixture screw should be.

The Stage one kit is for the stock airbox with a stock air filter or an aftermarket filter, and a stock exhaust or an aftermarket exhaust with high flow baffle.

The Stage two kit is for a modified airbox (removes the airbox lid) and a stock air filter or an aftermarket filter, and a stock exhuast or an aftermarket exhaust with high flow baffle.

If the kit is installed according to the baseline settings for your altitude 90% of the time it will be jetted correctly. If you do have a problem it is usually just a simple needle or main jet adjustment. If you have any questions or problems you can always call our Tech support line Monday through Friday 8am to 4pm PST at 1-800-992-4993.


If you want to see my pipe go to http://home.earthlink.net/~gellett/400ex


My settings.
Dyno needle on third notch.
Pilot42
Main 170
Holes in air box lid.
Stock filter.

At this point this carb is about topped out.


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My opinion and also a good friend, don't mess with the pilot just up the main jet! then see how it is. Good luck

Jera '00 400ex

 

hey TRX-430 -- where is the needle clip everyone talks about - i got the 150 on there- but I think ill slap on the 165 or 170 tomorrow

got some info on this - that would help. Ive had the 300 and 400 and never messed with the needle adjustment.

did you have to mess with the air mixture --- is that the screw on the carb - that has a funny twist to it --- kind of a 'J" type hose coming off of it -- on the bottom i saw one when i swapped the jets this afternoon.

thanks!

 

Wow - i never messed with the Needle - i changed the main already - but where's the needle - (rookie)....
Is there any free info on this - i can probably do it - if i knew where it was.