Backfiring Tons and Not Running...

[PoopOna400EX]

I have a 2000 400ex that I haven't ridden in 1.5 years. I started it up today and it backfires all the time and will just die out when I give it any gas in 1st gear. It seems to rev find in Neutral, except the horrible backfiring, but when you give it the gas under load in 1st, it drops all power, then will sputter back to life when you let off the gas.

I have checked the carb to make sure it was seated fine. I emptied the gas tank and put brand new gas in in case it was bad gas.

Also, it will not run with the choke off (lever in the complete down position), even after warming up. It will backfire even more and then die.

My next thing to try will be to replace the spark plug, are there any other ideas? The bike rode fine a year and a half ago, so I'm not sure what would be the problem.

I also put a new battery on, but that shouldn't affect anything.

Any advice is appreciated.

Thanks.

[AtvMxRider]

You are prolly going to have to take the carb apart and clean it real good. Also clean the air filter or replace it. Replacing the plug and change the oil would be a good idea.

[Aceman]

Your running way lean. Your best bet is to remove the carb and spray all the passages out with compressed air and carb cleaner. Chances are you got some grit or jelled fuel plugging the carb up making your bike run lean. Don't do anything until you clean the carb out.

[hondafox440]

Honestly, I think it is time for a complete overhaul.

How did you store the engine? Did you just leave it in the garage as is, or did you correctly winterize it? If it were my rig I would pull the cylinder and check for rust. Change the oil, and give the carb a good cleaning. Chances are the rest of the bearings on the machine will need some attention too..

[PoopOna400EX]

I already changed the oil. I think tomorrow I'll tear apart the carb and put in a new spark plug, or maybe in the opposite order. The way it's running, it really seems like an air leak on the carb, I just couldn't spot it.

I just kept it parked in the garage. I don't think there is going to be any problems with the bearings or cylinder, but you never know I suppose. First things first, spark plug, then carb and I'll see how that goes.

Thanks for the info.

Jason.

[hondafox440]

It may sound stupid, but check the air box/boot for a nest. I have hear of several cases when bikes have been stored for a long time that mice or birds have actually made nests inside the air box or air boot.

[PoopOna400EX]

Now that wouldn't surprise me...darn mice. I do run across them now and then and for some reason they don't like my mouse poison, so they don't eat it.

The airbox looked pretty clear, but I'll have to look inside the filter and boot to make sure...do you think it would make it backfire though?

[2004TRX450R]

guranted it needs a carb clean. no doubt in my mind. The cylender is probably OK though. Just clean the carb and stick a new plug in it and you will be good to go!

Check the complete air intake system. I've landed jumps before and knocked the boot loose from the carb. Ran like poop just like your describing. I'm sure it's an easy fix your not looking in the right place..;)

[PoopOna400EX]

Rico
Ran like poop

Rico, please don't use my name in vain...

Well, I think I figured the problem out. When I tore apart the carburator, the main jet was just laying there, I think that would cause a major leaness problem :huh

I went ahead and threw in a 155 main jet and a 42 pilot, that should make it run better since it seemed to be running a little lean with the WB E-Series and K&N Filter. Also put in a new spark plug just for giggles. I'll see how it goes tomorrow.

Thanks for the input guys...

OVER AND OUT...

POOP.

[cals400ex]

yes, that is a problem i see more than you would think. without a mainjet, i don't see how it would run lean unless the needle jet holder doesn't stick far enough down in the bowl to suck fuel.