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Discussion Starter #1
Hello out there. I'm new to this forum and looking for a little help. I have read a bunch of the posts and it looks like there is a lot of experience here. We just bought a 2005 Trx400ex and I am having a problem apparently with the air box. It ran pretty good when we got it home and then about three days later it acted like it was loading up and trying to flood at higher rpms. Breaking up and sputtering. Low r's it was okay. I changed the plug and it still did the same thing. I discovered that if I ran it with the lid off the air cleaner box and the air cleaner disconnected, the thing runs like a raped ape. I have checked to make sure there is no blockage in the intake system and the air cleaner looks good. Could this be a vacuum problem or is there something about these that I need to look at instead? Thank you for any words of wisdom you might have to share.
 

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Sounds like its jetted rich. Does it have a stock Air filter?
 

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Also what elevation are you at?Where did you buy the machine at?
 

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Agreed^^^^ My buddy's is jetted at 170 with box lid off and up on hole on the needle running it with the box lid off is fine but make sure you have a good air filter, K&N or UNI.

Also are you running stock exhaust? that makes a difference in jetting as well
 

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FYI, Honda stock filters are made by UNI. I agree, Where did you buy the machine and where do you live? You are definitely running rich. What does your spark plug look like? Brown, white, or black and wet?
 

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Discussion Starter #6
I'm at normal elevation, northern SC, I got it from a friend of my wife's, and it is all stock as far as I can tell. I would agree that it is runnning rich as there is quite a fog coming out of the carb when I rev it up high. It had been stored for quite a while and not ridden much when I got it so I figured that there would be a few things I would have to do to it to make it right. How much of a job is it to rejet it myself? I haven't messed with carbs much other than lawn mower (Briggs) engines and these are much different. Does the K&N filter systems add more power or just make it breathe easier? Thanks for all the quick responses.
 

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K&N adds a little more power and helps breathe better. rejetting is easy just pull the nut off the bottom of the carb get you a 7mm I think socket and inside that hole is the main jet. besure when you re-install it not to over tighten it they are fragile. I reall would give it a good cleaning though. Look on the jet you will see a number tell us what it is when you get it out. Are you running aftermarket exhaust? if it's 170 or lower I would put it back, leave the air box lid off and ride on.



I'm at normal elevation, northern SC, I got it from a friend of my wife's, and it is all stock as far as I can tell. I would agree that it is runnning rich as there is quite a fog coming out of the carb when I rev it up high. It had been stored for quite a while and not ridden much when I got it so I figured that there would be a few things I would have to do to it to make it right. How much of a job is it to rejet it myself? I haven't messed with carbs much other than lawn mower (Briggs) engines and these are much different. Does the K&N filter systems add more power or just make it breathe easier? Thanks for all the quick responses.
 

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I completely agree with what he said. But it is a 6mm, not 7mm deep socket.

What is normal elevation? The normal elevation here is 5280ft. A quad comes from the factory jetted for sea level. For every 1000 ft you go up, you drop one main jet size. If you change your intake(put on a K&N) you will have to rejet the entire carb. If all is stock, you can just change the main for elevation adjustment. I would pull the carb and clean all the little nooks and crannies.
 

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Discussion Starter #9
Just out of curiosity, what is your feelings on fuel additives for cleaning the carb. Something like STP cleaner? A friend told me that he had a similar problem and ran a tankful of fuel with STP in it and puttered around and it pretty much cleaned itself up and started running like it is supposed to. It did run good the day we got it home (about 2 weeks ago) so I assume it is just a little gunked up. Is it worth a try before I tear into the carb or is it a waste of $$ that might lead to other problems later?
Oh, and we are 568 ft above sea level.
 

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SEAFOAM!!!! the best on the shelf bro I use it in every engine i got, also FYI do not run any fuel less that 89 octane I run 104 but Im heavily modded too, alot of the guys up here I think run mid to premium low octane will also cause poor performance.
 

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making me look bad in front of the newbee? I couldn't remember 6 or 7 mm :icon_censored:



I completely agree with what he said. But it is a 6mm, not 7mm deep socket. QUOTE]
 

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Discussion Starter #12
Don't worry about being 1 mm off, I wouldn't hold it against you. About the seafoam, I have read a bunch about it and it looks like there are many for and against it. What mix do you use in the fuel? How often do you use it?
 

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Seafoam is amazing. I only use that and Techron...that's it.
 

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I usually put about a 1/4 can in my quad every third fill-up. I dump abput 2 to 3 cans in my boat, during the tuneup on my boat i pour it directly into the carb to clean the intake and carb out. I run a can in my wife's van twice a month keeps the gas mileage up. I catually gained about 1.5 roughly to the gallon plus I nitrogen filled the tires and gained 3mpg. I went from 24 mpg on the highway to 27.5 sometimes 28 depending on the trips we take.
 

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Thanks for all the help, gonna get some sea foam tomorrow and try it out. Might try it in my pickup as well if it works well in the 4 wheeler. I'm planning on putting in a K&N filter relatively soon and will have to clean and rejet anyways but if I don't have to right now, all the better. Has anyone got the air cleaner cover by K&N (at about $105) and what do you think about it? Thanks for all your help, guys. Sometimes just seeing/saying it out loud helps work it out the most.
 

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More clean air= more power!
 

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