Instructions on changing a Honda 400EX Pilot Jet. (Cures Cold Starting Blues)

[GPracer2500]

I don't remove the carburetor. I just loosen it enough to turn it to the side just enough to allow access to the float bowl screws with a small screw driver. No need to remove all that plastic.

The picture of the two pilot jets above: the one on the left is a series 26, the right one is a series 21. The 400EX carb actually takes a series 26 but a series 21 will work.

I'm with 400exrules about the float bowl screws. I actually replace nearly every screw on the carb with allen head bolts. That way it's easier to get to them with a ball-end allen wrench. This really helps when changing the needle. You have to be careful about overtightening though. They make those philips head screws soft on purpose. The idea is that the screw head will strip before you can damage the much more costly carb body.

[Chris 75]

cant you access the pilot by taking the bowls drain plug out? it is right next to the main on all my keihn carbs I ve never taken the bowl off to access the pilot. Drain plug is a 17mm that would save you from those 4 screws that are so soft. And with a small enough screwdriver you might not even have to cock the carb I dont know what the spacing is on a 400 though between bottom end and carb.

if im switching from one aftermarket exhaust to another, is this all i need to change?

[400eXr1d3rZ]

No, if you already have a 42 pilot jet and already a 155 or so main you wont need to change anything at all, depending on what the situation is. If you going from slip on to full, you need to go up a jet, ex: 155 to 160.

[AbnMP13]

This is awesome, now someone just give me enuf patience to wait for the new needle and HMF exhaust to come in!

[AbnMP13]

The new needle came with a brass in color, close to 1.5 inch long fitting of some type. Any clue as to what it is?

I'm swapping needle for needle so I assume it's not needed.

[casey_lamm]

Im about to do this for the 1st time. Where did the pictures go?

Is there this list somewhere that the pictures work?

My riding Alt is about 1000ft asl to a max of 2000ft. Typically 1400ft or less

Just trying to figure out what to get so I can get started.


Also please advise

have gotten alot of help from others as to what to do with my stock 07 400 ex.

1st mods to be installed...I decided to go ahead and do it myself after some gentle poking from other members.

K&N Stage 1 Power kit with Dynojet kit.

HMF slipon.

Thats it. I want to jet it after installed those 2 mods.

What do you think would be a good size to start with?

Also, should I do anything to the idle setting and stuff like that.

Give that this bike is new and im adding that stuff...walk me through what I should do and I how I should tackle this project.

I have some pretty good diagrams and pictures of how to do the jetting...but want some people who have done it to talk me through it so to speak.


Thanks in advance!

[f4iracer]

Originally posted by 400exrules
i would like to HIGHLY recommend going to home depot and getting some stainless bolts to replace the 4 crappy brass ones that hold the bottom of the carb on in pic #1. the heads of the brass ones strip very easily

What size bolts are those? You guys weren't kidding about those bowl screws, they are crap! I'll be lucky to get mine off the next time i go to re-jet, haha.

I don't think there is anyway to not stip those screws at least a little when you're trying to get them out or put em back on. I did everything I could not to strip them because I knew in advance that they were soft, but i still stripped a couple of them a little bit.

[AbnMP13]

Originally posted by f4iracer
What size bolts are those? You guys weren't kidding about those bowl screws, they are crap! I'll be lucky to get mine off the next time i go to re-jet, haha.

I don't think there is anyway to not stip those screws at least a little when you're trying to get them out or put em back on. I did everything I could not to strip them because I knew in advance that they were soft, but i still stripped a couple of them a little bit.

I bought hex head ones from Lowes and they work great.

[f4iracer]

what size are those bolts anybody?

Also, i've got the 42 in. I still use the choke though when it's this cold out.

From what everybody else was saying i thought the 42 would fix the cold start blues. It helps the quad idle a little sooner after warmup, but i still use the choke even with the 42 pilot, otherwise i have to crank it over too much.