2006 400EX jetting/carb rebuild - Honda TRX Forum
 
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post #1 of 9 Old 03-16-2019, 04:25 PM Thread Starter
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2006 400EX jetting/carb rebuild

Hi. I recently purchased a 2006 400. It has an HMF pipe and jets I'm assuming. The kid I got it from is 16. I don't think he put everything in right. When I got it it ran ok but it was winter and I didn't use it much. I started it up a few times for this and that and it ran. Now it starts and won't idle. It will run wide open, but no idle. As soon as I let off the throttle it dies. I'm guessing it needs a good cleaning. Probably idle circuit. I'm not a fan of mods myself. Honda is smart and I think things should be left alone, but that's me. The quad is fast enough and I don't ride trails. I live in NH and I ride on mine and neighbor's property so I wanna get rid of the loud pipe. I have the stock pipe to it. My question is can I just buy a rebuild kit and rebuild carb to stock and put stock pipe back on and get back to normal? No other mods on quad. I'm very mechanical, but never rebuilt a quad car so I don't know much about jetting. Thanks. I tried to find answers before asking, but all questions are more about modding than going backwards.
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post #2 of 9 Old 03-16-2019, 05:20 PM
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Just get an All Balls or Shindy carb kit - both come with stock jets - if you don't ride regularly, use non-ethanol fuel or at the least use Liquid Performance Ethanol Equlizer - if you don't have either locally available, you can order the EE on line - if you din't use the EE, dump the ethanol blended fuel every 3 weeks - drain it out of the quad and dump it in your car or truck - ethanol blended fuel deteriorates rapidly - it can be stored for 100 days under ideal conditions (ideal conditions being in a sealed steel or glass container in a cool place where the temperature doesn't vary more than a few degrees. Changes to the exhaust does not require rejetting the carb - changes to the intake affect jetting - just putting in a K&N filter may require rejetting to compensate for the lower restriction air filter - taking the top off the air box just complicates the situation even more.

The no idle situation usually indicates a clogged pilot circuit - cleaning the carb with a commercial chemical soak solution takes care of the problem
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post #3 of 9 Old 03-16-2019, 09:10 PM Thread Starter
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Thanks. I don't think you can get gas with no ethanol. As for those carb kits, are they all stock or "come with" stock jets? I ask because I wouldn't know one from the other inside the package. I don't know the stock sizes. Is there a chart somewhere? It's always been my understanding that if you change to an aftermarket pipe you have to jet the carb. It seems that's what everyone does. I just wanna go back to stock with it. I'm not into loud. Thanks for the info
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post #4 of 9 Old 03-17-2019, 01:45 PM
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You can get gas without ethanol - you just have to shop around for it - I was buying VP Racing SEF 94 octane from NAPA, Big R Farm Store or directly from VP Racing. The killer was I had to pay a $50 hazardous shipping fee + UPS shipping charges to get it shipped from VP. Or I had to drive about 12 miles or more to get ethanol free 91 octane at Casey's General Store's in neighboring towns. Last year Casey's built a new store in our town, now I just drive across town and to get ethanol free fuel. Casey's realized how big the market was for recreational fuel and is capitalizing on it. All seasonal engines should be run on rec gas. Motorcycles, snowmobiles, lawn mowers, snow blowers, stand-by generators or any engine that may be unused for more than 15 days needs ethanol free fuel in it's tank.

Yes, 'rebuild kits' have stock jets. Dyno-Jet kits usually have an assortment of jets for the installer to choose from. And yes, most people think they need to rejet when they change exhaust systems, but it's just ignorance on the part of the consumer and promoted by the sellers of "performance" exhaust systems. Ignorance is the presumption that more fuel equals more power. Just the opposite is true. Power comes from the heat of the burn (BTU's). A rich mixture burns cooler and is easier to ignite. Thus, cold engines need a richer mixture to start. The hotter the engine is, the less fuel that is needed to generate the desired output. The phenomenon escalates until the engine burns up. The heat generated is controlled with the cooling system and air to fuel ratio. The richness of the mixture is controlled to maintain a heat level the engine and cooling system can absorb and dissipate. Make sense?

The exhaust system carries heat out of the engine. Changing the exhaust to a free-er flowing system allows more heat to be carried away from the engine, but only at high RPM. The amount of heat getting out of the engine at low RPM is relatively unaffected. So rejettng for a free flowing exhaust is usually only needed for high speed operation. General rule of thumb is to jet up two sizes on the main jet for a change to the exhaust and in the majority of cases, no change to the idle or mid-range settings are needed.

Changes to the intake affect the entire range of engine operation, but idle is usually compensated by simply readjusting the fuel screw and mid-range may be fine without change, but the main jet may need bumped up 4 sizes or more depending on the extent of modifications.

The stock jetting was a #38 pilot jet and 142 or 148 main jet depending on altitude. 142 for high altitude. These jets are adequate for normal operation, but a performance freak will adjust for optimum output at the altitude and air density in his locale of operation.

Is there anything else I can help you with?
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post #5 of 9 Old 03-17-2019, 11:33 PM Thread Starter
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Thanks for the info. I'm gonna try to just clean the carb as is and see if that works. I'll rebuild it as last resort. I just wanna understand more about it before I open it. Carbs were never my thing, no real experience with them. Once I get that I'll move onto the seized rear brakes lol. Oh, I bought that Shindy kit so I'll have it if I need it. Thanks again
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post #6 of 9 Old 03-27-2019, 08:55 PM Thread Starter
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Hey. So I tried rebuilding the carb and failed. I suck at carbs, lol. I tried replacing the air/fuel "D" shaped screw and I couldn't get the new one in. The O ring that comes with it just won't fit in the bore. I tried to push it in and now it's stuck. I'll have to get that out somehow. There were only a few O rings and several were one size and a couple smaller ones. The one I put on doesn't fit and the smaller ones didn't seal it so I'm not sure what's wrong. maybe I'm missing something? Also I'm curious, I keep reading about the needle valve and putting the clip in the third groove, even the repair manual mentions this yet my needle has ONE groove! The needle that came with the kit also has only one groove. This is my life, nothing that works for anyone else ever applies to me, I have that luck where I find unique problems, lol. Appreciate any info. Thanks


Rich
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post #7 of 9 Old 03-27-2019, 10:59 PM
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So you got the D headed screw out - that's usually the hard part

The o-ring is not that difficult - the smallest o-ring in the kit is the one to use on the fuel screw

Did you get the washer and original o-ring out of the pilot screw hole? The easy way to remove the washer and o-ring it to tale a straight pin, safety pin or something similar, bend the point 90 degrees and use the little hook you just made to fish the parts out of the hole. Don't worry about the seal on the o-ring, it's just there to assure a accurate mixture - you can adjust without it, but the setting will be different than what's in the book.

The slide needle (if adjustable) always starts with the clip in the middle groove - wait till you get a kit with a needle with just 4 grooves - with a single groove, its easy - just put the clip in the groove - done
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post #8 of 9 Old 03-28-2019, 07:57 AM Thread Starter
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Ok. I thought the needle should have like five grooves. Everything I have read says five and other people have asked in other threads what groove to use but I only have one groove. Like I said that's my life to have something different.

As for the pilot screw, everything came right out with the screw but there are two O rings on it. The smallest goes at the tip of course but the second is bigger. The problem is the biggest in the kit won't fit in the hole and the next one down leaves movement so it doesn't seal. The screw is stuck in there now so I have to get it out. Then I'll try to figure it out. Carbs suck! LoL
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post #9 of 9 Old 03-30-2019, 10:37 PM Thread Starter
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OK so I got carb rebuilt and quad running. Backed the pilot screw out 2.5 turns like book says. Got it running and set idle screw so it would idle decently. I just have to fine tune it I guess. I'll have to mess with pilot screw to get it right. if I jam the throttle it wants to die. It works if I do it gradually, so I need to adjust that. Thanks for your help. On to the rear brake issues!!
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