400ex stalls on hills and turns ??

[lohman]

I was wondering if any others have had problems with their quads stalling and sputtering on hills and hard turns. I have a stock '99 400ex, stock pipe, jets, airbox, it does have a K&N filter, and when riding around our farm it stalls and sputters when climbing steep hills, popping wheelies, and making hard inclined turns. I read some other postings here, do you think it could be my float, or float level? Is that adjustable? or do I just replace it.

I just took the carb and gas tank off, drained and cleaned everything thorough, jets, needle and seat, filter in tank, etc. and put it back together and it still stalls and sputters when jumping, small wheelies, and climbing any decent hill.. Thanks for any help.


ps I also put a new spark plug in it, and it did not appear to be rich or lean. No hard starts or problems idles, or smoke, other than being cold natured, which I read is common. Also when it does this, sputters, I have tried to choke it, but makes no difference. It does not stall completly, just a bad stutter that causes me to stop, then pump the gas a few times and it clears out.

-lohman

[RAPTORAZ]

Sounds like your float level is too low.

[lohman]

Raptoraz,

You think this is adjustable, or should I just replace ?? I will dig up the service manual...

Thanks for the quick reply, this forum is awesome !!!!

-lohman

[RAPTORAZ]

It wouldn't be a bad idea to replace it. I'm sure it's cheap enough. The reason it (the float level) might be getting low is that it (the float) has a leak and is filling up with gas. I've never had to adjust the float level on my EX. But I havn't seen a float yet that wasn't adjustable. I'm sure a service manual will tell you where to bend it to make the adjustment.

[300exjuggalo]

maybe your in too high of a gear maybe down shifting would be a good idea:D

[oynot400]

Check your steering stem. If there is water in it and you bring it up on a wheelie or climb a steep hill it may block the gas tank vent tube. That will make it sputter like it is out of fuel. Check the vent tube for any other obstruction, such as dirt, golf tee's, tied in a knot, ect. Someone could be playing a little joke on you. ;)

[cals400ex]

i think in 2001 they changed the float for this same reason. my friends was doing the same thing and he put in a float from a new bike and it has been fine ever since. his would leak gas from the tube off of the carb pretty bad while just riding wheelies.

[froggy97]

check the vent tube that should plug into your heat sheild from the carb
mine did the same thing it had fallen out and become clogged with
mud

[danney f]

I had the same problem on 2 differant ocasions. The first time it was the vent tube on the top of the carb, it had got cloged with mud and the second time the vent tube that comes off the gas cap had got pinched. If you haven't messed with float yet check the vent tubes first. Hope you get it fixed.

[lohman]

Wow what a great group of people. I check my vent tubes, and one of them has a small bolt in it, from the previous owner. Not sure what to do with it, if if vents freely, or needs to be plugged in somewhere. Here is the description. It is on the same side as the choke and main fuel inlet, in fact it is about middle way up, above the main fuel inlet. In looking at the service manual it just calls it a vent tube, and might plug into the top right side of the carb????? Should I just leave it unplugged (I have taken the small bolt out of the end) or try to plug this thing into the carb somewhere. The tank vent is free and not clogged, but this one on the carb sure was....

To cold and dark for a test ride tonight, but I am sure this is it because when we had the carb off the float was not cracked or anything..... This is great !!!!

-lohman

[lohman]

Just to let everyone know, getting the vent tube unplugged worked !!! No sputters or lags...

Thanks to everyone's advise I think I gained 20 hp :P

-lohman

[AtvMxRider]

Good to hear.

[countypark]

Check your gas tank for water. When you go up a hill or pop a wheelie the water will run straight into the fuel line pick up and stall your engine. It took me two races to figure out that problem. Drained the tank and it was full of water. Ran fine on the flat stuff. Only messed up on hills, and believe me it can get ugly on some of the hills at Big Game.

[250fox]

my 400ex is doing the same thing. dies when you climb hills or turn sharp. Soo....the floats are not adjustable? I have checked everything else. Water in tank-no, tubes clogged-no but when I took the carberator off and pushed the float up it cuts of about 1/2 from the top. Also if you shake the wheeler front to back it does the same thing (not rolling) HELP!