[Andy Archdale]

I just picked up a 2004 400ex for cheap. Gut says it was bored out when rebuilt 7 years ago. It starts and idles fine. I can ride around as long as i dont really throttle it. When i give it to much gas it starts to sputter and cuts out. Im rebuilding the carb now, what else should i look in to. The air filter was absolutly filthy and looked like gelatin in part of it. Its all clean, waiting for the carb kit and accelerator kit to come it. It doesnt smoke or anything like that, just cuts out under throttle

 

[SamUK]

Welcome to the forum

While your cleaning/rebuilding the carb be sure to clean the tank and replace the fuel line at the same time, don’t forget to add an inline filter too.
I’d be tempted to change the spark plug and air filter at the same time, maybe even an oil and filter change, you never know if fuel has made its way into the oil.

Also, AVOID ethanol gas! That will cause all sorts of carb related issues over time.

Hope this helps.

 

[alloutdoors]

Very good advice from SamUK and betting you have a plugged jet. Did you order a genuine OEM Honda kit? When you get the carburetor out, do not underestimate how clean everything needs to be for it to run perfectly and would do everything SamUK mentioned to get things cleaned in the tank/line. As for the carb, I would go ahead now and prepare a solution to soak/clean things well before the items come in.

 

[LedFTed]

welcome; i especially like the part, to make sure your carb, is cleaned. run into this myself..

 

[Andy Archdale]

thanks guys, I cleaned the air filter real good, and i did and oil change, and will for sure get a new spark plug. The only markings on the Carb are Kei Hin. Is that a Honda Carb?. I have it soaking in carb cleaner. IT didnt look bad at all, Ill still rebuild though for piece of mind. The bike has all new fuel lines, although i dont see a filter anywhere

 

[Goober]

You can click the parts links in my sig block to find part numbers for your quad.

Your carb will have two part numbers. One is listed in the service manual the other is commonly used in the parts listings

QB10AB should be stamped into the side of your carb, followed by three letters which indicate when in the run you carb was made, and a last odd looking character

 

[Andy Archdale]

THank you, got everything ordered. The air Filter on mine is a K&N, i read somewhere that these dont work well on the 400ex, makes them run lean. Is this true?

 

[Goober]

I can’t say this is an absolute for your machine but I suspect Anytime you make it breathe “easier” you’re likely to upset the fuel air mix. This system doesn’t have an O2 feedback system so it can’t compensate for the higher airflow.
You might be able to find a larger main jet.

 

[LedFTed]

welcome; i especially like the part, to make sure your carb, is cleaned. run into this myself..

its not stupid to ask questions, its stupid not to...

 

[Z7What]

Just a little off topic, but i have a friend of mine that said he boils his carbs to clean them. Have any of yall heard of or done this before?

Wayne

 

[mrbb]

a compression test would be on my list of to do's here, 7 yrs ago is a LONG time on a top end, and well, sounds like the old owner wasn't that great on keeping things proper and clean, if that air filter was so clogged up, it could have cause something to get past it and into the motor, and well ruining a top end !

so a compression test would be at the top of my list, and before cleaning any carb or anything down stream of tank, I would be draining tank and making sure tank is clean, as if you skip this part, cleaning a carb can be a waste of time as crap in fuel will be right back in and dirty the carb back up after cleaning it??

have to start up stream to rule that out before cleaning down stream>?
start at tank, then peacock, then fuel line(only the new Yellow line is ethanol approved ?? its cheap and rules out build up of crap in the lines ) THEN clean carb! other wise again you can be wasting your time cleaning JUST the carb1

 

[Andy Archdale]

Whats the best stuff to use to clean the tank?, Acetone, Carb cleaner. Ive read of all kinds of different things. THe guy said it was rebuilt 7 years ago but he didnt use it for a few years. Ill still do a compression check when i change the plug. Ive been out of town for a week so i havent been home to mess with it yet

 

[LedFTed]

Just a little off topic, but i have a friend of mine that said he boils his carbs to clean them. Have any of yall heard of or done this before?

Wayne

might work, but a mineral deposit, like when you have used ethanol gas, even if you didn't, wont come off, that takes cleaning of the elbow kind.
just an opinion...

 

[Andy Archdale]

Just wanted to update on my post, Put it all back together and it runs great. Cleaned carb, and gas tank. fresh gas and a clean air filter. seems to run great with lots of power, had a little issue with the carb over flowing, but i resolved it quick. Thanks for everyones help