Another carb question....

[Muffer Bearing]

I have an 02 400ex. (bought it used) It has a WB E pipe. I am guessing the header pipe is WB also cause there isn't a heat shield or a place to bolt one on to. Anyway, it also has a WB air filter. The other day I checked the plug and it's running to rich. I pulled the carb down to see what jets were in it and I had a 146 main jet and a 38 pilot jet. Stock is 38 correct? Well, what is a 146? (rich or lean from stock?) I don't even know what brand it is.

I bought the little UNI air box inserts and was going to try to lean it out a little before screwing with the jetting. I think they come 6 to a pack and are about 1inch around. I figured I would start with 2 first and then add more if I needed to. Anyone ever used these before?

If my local Honda shop hadn't gone out of business I would have picked through their selection but now I guess I will have to find someone else that might have em

[Honda#4]

A 148 main is stock so your main is on the lean side, what I don't understand is why you ain't lean instead of rich cus usually when you add a pipe and filter your adding more air your leaning out the mixture.

[Muffer Bearing]

Hmmm, yeah that doesn't make sense. I figured it was on the rich side but then again I am not really familiar with the 400ex jetting. On a side note....I didn't do any WOT runs and shut it down and then check the plug. All I did was ride it for a while get on it a few times shut it down and checked it. The plug was completely covered in soot. It doesn't make sense. Could the 146 be a different brand like WB or K&N?

[GPracer2500]

What's the jet look like?

If it's a genuine Keihin jet it will have a stylized "K" in front of the number. Some aftermarket jets look the same as Keihin mains (the same "hex" shape) but they won't have the K. Some will just have a number with no letters or symbols while others have their own mark (e.g. RD Precision mains have "RD" in front of the number).

I believe Dynojet mains are round and they use an adapter since the threads are different than normal Keihin hex mains.

All aftermarket copycat-Keihin hex mains that I'm aware of use the same scale as genuine Keihin mains. Dynojet mains use a totally different scale. K&N, FMF, and maybe some other jet kit brands are just re-badged Dynojet jet kits.

[Muffer Bearing]

I am trying to remember but I think it was round and it did not have any markings before the number. What I do remember is the number 6 on 146 was hard to read it looked like an 8.

I still do not know why it would be rich with a leaner jet an air filter and the exhaust. The pipe has several rings on it also.....

Ah I think it does have an adapter on it! I remember it looking like a jet extention I have on my car...Now what?

[GPracer2500]

A 146 Dynojet is something like a 160 Keihin.

Bear in mind, if you've got a Dynojet main in there chances are there is a Dynojet needle as well. If you start using Keihin mains beware that combo isn't likely to jet exactly the same as if a Keihin needle is used. In other words, if your neighbor has an identically settup bike (except for the needle) and his is jetted perfectly with a XXX main jet, that doesn't mean that is the same size main jet you'd want to use. Maybe, but maybe not. I've never seen anything definitive about running a Dynojet needle and Keihin main combo in the stock 400EX carb.

BTW, I've used the little UNI airbox inserts. They're alright. I ended up leaving them out and just running empty holes in my lid.

[Muffer Bearing]

Good point on the needle. I guess I will dig a little further into the carb and see what I have. If I get another dynojet jet what size should I drop to? 2 sizes or 1 at a time? BTW, Thanks for the help. I want to have it running well for my trip next Thursday to Little Sahara.. Anyone else going to be there around the same time?

[GPracer2500]

2 sizes at a time ok. When you think you've got it close, then go one size up/down and test again.

I believe Dynojets skip every other number, i.e. 130, 132, 134, 136, 138, 140, etc. So, 2 sizes would be going from a 146 to a 142. Keihins go by 2.5, i.e. 130, 132, 135, 138, 140, etc. A 132 is actually a 132.5 and a 138 is actually a 137.5 but they label them with whole numbers for simplicity.

The Dynojet kit for the 400EX comes with a DJ134 all the way up to a DJ170. Only a seriously modded engine would need anything up around a DJ170 (that would be somewhere around a K190).

[Honda#4]

I run dynojet's in my 400 with the stock needle so far I haven't developed any problems, I have a WB slip on and I run a DJ 142 which is equal to a K155 main with the WB Power filter and the lid removed.

I bet you are rich on the bottom but if you would go WOT you probably would be lean with the jets you have in right now.

[Muffer Bearing]

Well, I took the carb apart again earlier and confirmed it indeed has a round jet with 146 stamped on it and it does have an extention. I guess from everyones input it is a DJ jet. I tried to take the needle out but couldn't figure it out this time around. I wanted to verify the clip was on the 3rd slot. Well, I guess I will look for a DJ 142 main jet and see how that works out. I still have the stock 38 pilot jet so why would it be rich at idle if the main jetting covers more of a range? Main jet covers 1/8th -3/4 or do I have it wrong? Thanks again..

[GPracer2500]

0 - 1/4 throttle: Pilot circuit (pilot jet and fuel screw)
1/4 - 3/4 throttle: Needle circuit
3/4 - WOT: Main jet circuit

There is overlap between the circuits but each circuit dominates the fuel metering for those throttle postions.

[Honda#4]

I think you have your pilot screw out to much thats whats causing your richness at idle.

[Muffer Bearing]

GPracer2500.... I figured I would be wrong, thanks for the info.

Honda#4.... What should it set at 2 1/4 or 1 turn out?

A different question for you guys. Where can I get an oil seal for the crank case cover and one for the clutch linkage also for the crank case cover? My local honda shop went under and Rockymountain doesn't have them. Thanks again

[Honda#4]

Service Honda I'm sure sells that stuff that anyway would be my best bet.

For your pilot I would set it at 3 turns out from lightly seated. If thats to much turn it in a quater turn at a time till right.

[GPracer2500]

HERE (http://www.exriders.com/vbb/showthread.php?s=&threadid=229923) is the best method for tuning the pilot ciruit. The only caveat to using that method is you must have access to the fuel screw adjustment while the engine is running. But that method takes the guesswork out of getting it right.

[Muffer Bearing]

Thanks GP, I read that last night after I had already posted. Great write up.

Honda #4, I checked last night and it was 3 turns out already so I blindly set it at 2.5 turns. When I get it back together here in the next day or two I will try the engine running method. Thanks for the help!

[Honda#4]

2.5 turns should be ok if not try 3, and your welcome for the help if you need anything else just ask.

[Eviltanker]

Hey bud,
If you want to go to Keihin style jets(JetsrusJets) I have a 155 and a 158 that would help. Also what elevation are you at?not to pick on you but, I went through the same thing! elevation has a lot to do with your jetting as you probably already know, Also your temps play a big factor. To point you in the right direction we need these things. I'm not a big fan of Dyno jet but, it is user preference. I run jets r us or actual Keihins(C&D Racing) in any job I do. If you need advice you are in the right place. It all comes down to looking at all the responces and then taking them into consideration then buy about 3-4 plugs, and jets from 148 to 158 keihin and start jetting and plug chopping. I learned it from GP and have found it is THE Best way to do it.the whole $15 is worth it when you are running perfect.