bottom end issues

[95300exrida]

My 400EX doesnt have anything close to the bottom end that all of my friends quads have. I have to rev it quite a bit for a four stroke to get it to pull like how my friends quads do at alot lower rpms. and it sputters and cuts out sometimes too like its misfiring. all it has on it is K&N filter and it used to have holes cut in the airbox but i taped them up because it runs better with them closed. any help would be great guys

[400eXr1d3rZ]

Did you buy it used? The person you have bought it from may have went up a tooth in the front or dropped a few in the back.

[95300exrida]

yes i bought it used. what is the stock gearing on a 400ex?

[400eXr1d3rZ]

99 - 04 is a 15t front 05 - 07, 14t front.

And I think the rear sprocket is a 36t, either that or 38t.

[95300exrida]

k thanks ill check mine in the morning... anybody have any suggestions about the sputtering?

[firefighterjosh]

You need to jet it out since you installed the K&N.

[F-16Guy]

15/38 is stock gearing. Turn your gas off and let it run until it dies, then remove the float bowl plug on the bottom of the carb. If you have a dyno jet kit, the jet will have a flat blade screwdriver slot in it. If it's a Kehin, it will be hex shaped. Pull out the jet and post what size it is, what mods you have, and your location and approximate elevation. We should be able to get you closer on jet size. If you need a reference for where the jet is and how it's installed, click on the "Articles" section at the top of this page and click on the pilot jet article. It will have photos of where everything is located. If you need a different Dyno Jet, I have a few I might be able to send you. If it's stock, they're available at most motorcycle shops.

Also, you should consider checking your valve lash if you bought the quad used and have never checked it. If it's a '99 and it's never been done (it happens), it's definitely overdue.

[95300exrida]

k thanks im pretty sure its a 155 main because thats the only one missing from my dynojet kit but ill check to make sure. my elevation is 500m above sea level or about 1500-1700 ft above sea level.

[F-16Guy]

That sounds way rich. I'm running the DJ155 main in my 416, so you've got to be rich. I'd go down to about 146 and see if that helps. Also, make sure your filter is clean, and the needle clip is in the position recommended for Stage 1 jetting for your altitude (3rd groove if I remember right). DON'T go by the stage 2 jetting instructions!! Go by stage one and you will be much closer; more fuel doesn't mean more power unless you can burn it. I don't know who came up with their jetting guide, but he should have his ***** removed. Trust me, rejet exactly according to stage 1 instructions, clean your filter, and check your valve clearance, and you will have a new bike!!

[adinocr7]

Originally posted by F-16Guy
Also, make sure your filter is clean, and the needle clip is in the position recommended for Stage 1 jetting for your altitude (3rd groove if I remember right). DON'T go by the stage 2 jetting instructions!! Go by stage one and you will be much closer; more fuel doesn't mean more power unless you can burn it. I don't know who came up with their jetting guide, but he should have his ***** removed. Trust me, rejet exactly according to stage 1 instructions, clean your filter, and check your valve clearance, and you will have a new bike!!

F-16Guy:

You're right, the instructions tell you to do the "Stage II" setup even if your ride is still bone stock like mine. I've got a Dyno Jet kit for my 06' TRX450 coming in any day now. I downloaded the instructions ahead of time just to get ahead of the game. I thought it was strange that the .pdf file is only for Stage II. I would have gone strictly by these instructions as I figured for an aftermarket kit its normal. The only thing I've done is pull the baffle because I like the sound and it feels less sluggish.

Just wanted to say thanks for saving me a potential headache. I'll post a response to how it runs on Tuesday.

[adinocr7]

I just received my Dyno Jet Kit today when I got back from lunch (I have my parts delivered to work). There are no "Stage1" instructions, just stage two. I went to their web site and downloaded the .pdf file for jetting instructions. Its only for Stage II as well; in fact its the same thing that came with the kit.

Can someone point me in the right direction and tell me where I can grab the Stage I jetting guide for my Dyno Jet Kit? It would be for an 06' TRX 450ER.

Thanks

[F-16Guy]

What I was talking about earlier was for the 400ex. Your 450R kit may have the correct jetting specs. I don't have a 450R, so I don't know. I would follow the directions and see how it runs. Did you get the leak jets, too?

[95300exrida]

hey i just rejetted my quad to 160 and its a whole new quad now no sputtering just pulls hard. and i did check and it is a 16 tooth countershaft sprocket.

[F-16Guy]

...now keep going down on the main jet a size at a time until you don't see any improvement, and then go back up to the next size up. That will get you really close with th main. If you don't have any internal mods (high compression piston, cam, etc.), I highly doubt that a DJ 160 main is lean enough. If you follow the instructions for Stage 1, it should be closer to a 146 main, needle clip on the 3rd groove from the top, and 2.5 turns out on the fuel screw. The biggest mistake that most people make with jetting is thinking that more fuel equals more power; it doesn't. The right ratio is the key. Follow my advice and you'll get a lot more power and better throttle response.:macho

[adinocr7]

F-16Guy:

I have both my Dyno Jet Kit and a ~ 55 and ~ 50 leak jet. Everything will be installed this evening.

I was planning on installing one of the leak jets first just to see if the low end bog is taken care of. I figured it would be best to isolate one problem at a time. If that makes an improvement to the bottom end bog then I'm going to install the Dyno Jet Kit per their instructions. I have a small strip of land where I can take the machine for a quick 5 minute rip session before the neighbors start getting pissed. However Sunday I'll have a chance to really see what a difference the jetting has made.

I hope to have some good feedback for everyone come Tuesday.

[adinocr7]

Alright guys. I couldn't wait until Tuesday to post my test run results. I spent about 5 hours tonight testing and tuning and here is what happened. As I mentioned I purchased a Dyno Jet Kit and some leak jets. I installed the ~ 55 leak jet and took the machine for a spin. The low end bog was completely gone. However mid range was not 100% and the top end (3/4 - full throttle) would cut out.

The next step was the dyno jet kit. Well per their instructions (remove the airbox snorkel and then add the new needle) . . . not quite. I had to remove the front plastic and the gas tank. I was very impressed however at Honda's engineering . . . the body was a snap to remove and replace . . . and it did it about 1/2 a dozen times tonight.

Anyway I set up the Dyno Jet needle (e-clip on 4th groove). I also put in the new Main Jet adapter and the #124 main jet they recommended. I will also add I cut out part of the air box (the part with the snorkel that goes inside) and have no baffle in the exhaust.

Well low end was great. The midrange (1/4 - 3/4) throttle was insane! No here's the kicker. At full throttle the engine would cut out bad. It was definetely running lean on the top. The only two jets I had to work with were a 132 and a 136.

Now just for the record this is why I'm going to be going back to standard main jets by Honda. The Dyno Jets are not hex shaped so you have to use a flat head screwdriver to remove and replace. To make things worse the carb doesn't exactly slant out to the side so its not easy to add and remove. Thus with standard mains you can just drop the bowl, use a socket and within a minute you're set.

Anyway I tried a #136. The thing ran rich all the way through the power band. It didn't run like crap and didn't cut out at the top. However it didn't scream and pull hard like it did with the #124 main jet from 0 - 3/4 throttle. So I came back to my truck (magnetic spotlight mounted on side panel / my loyal friend by my side and my tools) and proceeded to try to only other jet which was a #132.

* * If these numbers seem a little strange if you're not familiar with Dyno Jets their main jet numbers are completely different then standard main jets. * *

Well it pull like crazy from 0 - 3/4 throttle and what do you know at full throttle it would cut out. So basically at this point I'm at a loss. The machine runs amazing at low end and the mid range is great. But I cannot for the life of me get the top end straightened out. At this point I'm going to do two things. First of all I'm canning the Dyno jets because they are a royal pain if you need to change jets and do some tuning. Second I'm thinking of just purchasing a complete HMF exhaust kit (which includes the proper main jets) and doing a high performance intake set up.

Now I haven't played with the fuel screw. The only thing I did was use the tool Dyno Jet game me and set it at 1.5 turns out. I'm not sure if messing with that would do anything for the top end. All I know was at 10:45 pm I had had enough and we decided to call it a night. Plus testing a machine on a back road at night hours isn't exactly the most legal thing to do. :huh

When I had my KFX 400 I threw on an after market air box cover and a full Yoshi Exhaust with a 165 main . . . ran like a top. This new 06' TRX 450 is the fussiest damn thing I've ever dealt with. Any advice on how to straighten my top end problem out would be greatly appreciated because I am stumped.

[95300exrida]

why would i keep going down on jet sizes when i went up and it got better?that just doesnt make any sense. you have to remember that i am at a low altitude and the air is very thick or dense or wtvr.