I've got a 2002 Honda 400EX, I've always had a problem
with it when it goes vertical. I am a wheelie fanatic, But
everytime I get my 400EX at 12oclock, there is gas
spewing from the overflow tube that runs to the bottom
of the bike, and the engine putters out. This is very
frustrating. I've got a 2001 Yamaha WR250, which I can
ride a 12oclock wheelie on for a quarter mile,
(sometimes even going past 12oclock) and it never has
any problems with bogging, putting, or spewing gas
from any overflow tubes. Does anyone has any
modification ideas which would enable my 400EX to
perform vertically the way my WR250 does?
Anything past balance point on my 400EX causes it to sputter out!

 

plug the hose.. but no matter what it will sputter out.. unless u are above liek 1/8 throttle then it will run no prob

 

I'll try plugging the tube. but no matter what throttle I am at, it still sputters out... Is it sputtering because of the carb float? would remounting the carb so it has a more forward tilt possibly correct the problem? I cant figure out why my WR250 runs fine vertical, there must be something on the WR250 allowing it to run vertical. If my 4 stroke dirtbike engine can do it, there's got to be a way to get the 400EX to run smooth vertical.

 

dont plug the tube, its one of your vent lines...you need the carb to breath...supposedly the newer 400ex, Z400 and other bikes done have this problem...i think it has something to do with the floats.

 

just get a catch can so you dont waste so much gas

 

+1 they all pee like crazy !!! The bogging down ?? I dunno ? Don't plug the line it will stop running !

 

I did the catch can thing and it filled up 2quick and as soon as it's full it stalles it out, so you have to empty it often !

 

You mean dont have this problem??

Do you or anyone know if the trx450r has problems running straight up and down?
Pleaze help!

 

You shouldn't have any problems on a 400 ex except the peeing. They are wheelie machines, with an easy button already installed !

 

mine would fill up in like 5 minutes if i was rocking idle ****. the 450r doesnt **** out that i know of and it does coaster like a champ

 

Does anyone know if I can put a 450r carb on my 400EX? would that solve my vertical bogging problem? My 400EX wont do coasters or anything, It's the worst quad for wheelies I have ever had, some of you claim your 400EX's are performing fine past the balance point? what year is your quad?

 

i have a 04 400ex and i can rock slow **** past 12 as long as i want with no bogging and i dont lose much gas at all. itll also do coasters without stalling out :YEAH

 

My 400 that is modded would not do it as well as my stock one !

 

i had a bone stock 2000 that was the best stunt quad i ever had

 

i used to stunt a kawasaki mojave it did the same **** i extended the overflow line all the way back under the axle so gas didnt get all over the chain and **** but **** it.

 

**** i also used to do coasters on my mojave and never had problems with the engine stalling out. just keep reving it.

 

I agree my 440ex is very powerful but it has so many problems, it pulls the engine studs out all the time, I had 3 top ends redone, I had it drilled from 10 mm to 12mm, it finaley is holding together it is just a pain and the 440 kit is a bad design and the studs in the engine are just short, there like 3in long only.

So a stock 400ex is the way to go or the 450R.

 

if your looking to just stunt it out get the 400 if you want something that is better rounded get the 450

 

Good gosh you all are crazy...a 450 carb is not made for a 400 EX (2 totally different motors and 2 totally different power characteristics) im sure theres a 10 mm difference in carb size. (I doubt it would even come close to bolting up) If you put a big carb on a little bike it may run good at high RPMS with it will run like crap in the lower revs because the intake suction is weak and cannot atomize the gas correctly. A smaller carb has a higher air velocity than a big carb on the same motor so a better fuel mixture will be achieved at lower RPM...one thing that really helps out is the Power Now...its gives higher air velocity in the lower RPM range than the same carb without it. Also adjust your floats for a lower fuel height in the motor this will prevent spewing and a super rich mixture while all the way back (which is why your motors cutting out) you ever notice black/gray smoke coming out of your exhaust after you come back far? Thats a symptom of too much fuel in the combustion process...Stay with the stock carb, make sure its jetted correctly (especially if you have a pipe or other mods) check that your airscrew is in the correct position, get a power now and if your skilled enough lower your float height (bend the float valve tab up)...good luck.

 

i read the whole page and had too wait till the end before any one said adjust your floats.......lol