99 400ex Trouble

[duvall45]

I'm having trouble with my 99 400ex. It is missing bad at mid range rpm. I have taken the carb apart and cleaned it 3 times (I found junk in it the first 2 times) and am still having trouble. I am thinking of taking the carb off of my 07 400ex and put it on the 99 just to make sure that the carb is where the trouble is. I don't want to change any settings, and it would only be for a couple of hours. Anyone see any problem that I might have?

Any ideas or help is appreciated. Thanks in advance!!

[finsteratv]

if you found junk in your carb twice then you should proably put in fresh gas and clean out any garbage thats in your tank. checked the timing? that may be why its missing, CJM WHERE ARE YOU (mechanical man)

[CJM]

Yes yes Im here Finster..

1. Dump the old gas out, start with fresh 93 octane. 93 is preferred, most of the time it contains less of that crappy ethanol.

2. The carb could still be dirty, did you clean the jets out with a small piece of wire, is the bowl clean, etc.

3. Is it 100% stock or have any upgrades like an exhaust, air filter etc.

3A. Stock jetting is 148 and a 38 pilot, the bogs in mid RPM so Id lean towards your main jet being to big.

You cant expect the bike to run 100% all the time. Temperatures vary, thus jetting needs to change to a degree. If you dont want to mess with your jets go and take it to a shop and pay them the 150 bucks or more to play with it.

Also if you pulled it apart 2x Id lean on there is junk inside your tank.

[duvall45]

Sorry I didn't give you all the info... The first thing I did was drain the gas and get fresh premium. I did get a UNI air filter this week and put it on, just to make sure nothing was getting through. Other than that it is all stock. The first 2 times I took it apart I found junk plugging the jets and when I put it all back together it would run great for a while then start cutting out again. The last time I took it apart I couldn't find anything, put it all back and it was still messed up. I thought about the timing but still not convinced it isn't the carb and I am trying to adjust only 1 thing at a time. I was thinking if I swapped carbs with my 07 it would tell me if it is the carb or I have other issues. The spark plug had quite a bit of carbon so I changed it out, but I think that was from previous owner running cheep gas.

Thanks again, your help is much appreciated.

[CJM]

Do you know what jets are in it? The uni filter wouldnt have caused it because it would make it run slightly more lean-not the rich induced bog you have now.

A carbon fouled plug means too rich, tan is good and white is lean.

[duvall45]

Didn't think to check what jets are in. The UNI was put in after the 2nd cleaning. What do you think of just buying a rebuild kit? I don't like to just throw money at it without knowing whats up. So if you think the jets too big what size would you suggest?

[CJM]

148 or 150 main and 42 pilot.

This chart will be helpfull: http://www.exriders.com/vbb/showthread.php?s=&threadid=445695&highlight=jetting+placement

It also depends on your elevation and the air temps. The sizes I recommend usually work at sea level to about 3000ft.

Upgrading to a 42 pilot will help alot, 400ex carb has way to small a pilot jet, 42 pilot will make it start wit ease.

[DragonGunner]

did you use carb cleaner for cleaning the carb? I ask because a friend clean his carb like 3 times...I asked that question an he said no, just a brush an air nozzle.....an inlign fuel filter ain't a bad ideal either.

[DnB_racing]

Originally posted by DragonGunner
did you use carb cleaner for cleaning the carb? I ask because a friend clean his carb like 3 times...I asked that question an he said no, just a brush an air nozzle.....an inlign fuel filter ain't a bad ideal either. the air nozzle is a must!!!but your right some sort of solvent is needed also, along with a full dis assembly of all the jets, make sure you blow out all passages,

I know you said you changed the plug , but have you checked it since to make sure its still dark?

sometimes people mistake a lean breaking down for bogging, when lean sometimes it will pop, when rich it feels like a rev limit and give that( bwooaa bwooaaa) sound..

make sure its still rich and not lean from a leaking air boot or a bad sealing carb

[eprovenzano]

Check your fuel line, has it aged to where its causing the debris in the carb? It’s a cheap replacement just to be safe....

[matts27]

You oil the new UNI filter? Seen too much oil put on foam filters and clog up even clog a carb so bad it cooked a motor.

Keep filing and draining the bowl into a clear glass container. That'll let you know if the tank and bowl is clean. Also, I'd make sure the accel pump is giving it a squirt of fuel when you get around half to 3/4 throttle. Just my thoughts, Matt