Please Help 04 450r Cuts out (with video)

[440challenger]

Hello all. I just got done putting a 04 trx 450 motor into my 06 400ex. Let me start off by saying the motor was low hours,i checked compression and valve adjustment and everything was spot on. This motor is completely stock.

I completed the build a few day ago,where on the street for the test ride it ran good,but need to be jetted richer .No big deal. Took it out the following day when this problem all of a sudden started... anywhere past 1/4 throttle it falls flat on it's face back fires and pick up again then falls on its face etc. It cuts in and out and in and out. Like i said both days were the same tempature,so this is not a jetting issue as the previous day it would rev out through every gear and just needed fine tuning.

I took the carb COMPLETELY apart,to find absolutely nouthing. Not a spec of dirt,a loose jet, loose screws that hold the needle in,NOUTHING. I still cleaned it otu and blew out all passages, just to put it back on and do the same identical problem. Intake before the carb is sealed tight and i also sprayed carb clean when running to see if i did have an air leak. I check fuel flow from the tank and it had a fast steady stream,no clogs there. For giggles,unhooked the tps,no luck. Checked the coil ground,all good. Quad starts first kick,all lights etc work. Im completely stumped on this one. I have added some videos on the following links below to give you a better understanding of the symptons. Bare with me its about 20degress i had no seat on and im by myself trying to hold the camera with one hand etc but they should give you a good idea. ANY HELP,or suggestions please post! I want to ride my new creation! :)

VIDEOS:

http://www.zippyvideos.com/2524031976629346/mov02261/

http://www.zippyvideos.com/3149069276629376/mov02263/

[400exrider707]

My buddy had this exact same thing happen on his quad.... I remember it started doing it really bad one day as he was going off the face of a jump... he would go off and then you couldn't hear his motor.... then he would land on his front tires and almost flip... we asked him what the hell he was doing and he's like Im full throttle! Ill have to ask him what it ended up being...

[440challenger]

Please do 400ex!!! Its driving me nuts!!!! its almost like its electrical

[1fst400]

It probly isnt the problem, but put the other jet back in. You know it ran with that one. that way you can narrow doun the variables.

[440challenger]

What jet? i didnt change a thing . The quad is exactly the same as the previous day i rode it when it ran fine.

[thump4863]

Check your filter in your pet cock - I had that problem once and thats where it was clogged at.

[440challenger]

I checked fuel flow and it comes out fine as i mentioned above. I took the line off the carb and then turned the gas on and let it run into a can and it had a steady good flow :confused:

[ss440ex]

Maybe lean...
try it with the air filter back on...
Then place the air box lid back on see if that helps!!
Keep us up dated.

[440challenger]

Ok well, i took it all apart again and checked all the wiring. Didnt find anything. I also ran it again with the headlight ON and watched the headlight when the motor fell on its face,to see if the headlight went out to see if the motor is loosing spark but it stayed bright the whole time.

up to 1/4 throttle is prefectly normal,any more gas and its just like you hit a brick wall,then it sputters,bogs and backfires. if i roll the throttle on at an idle it wil get up high in the R's but its breaking up very badly.

I was thinking maybe the acc. pump? Anyway to see if its working properly? I believe the acc pump is for just up to 1/4 throttle correct?
Idk, i am really pulling my hair out of my head with this one .


Lid on,filter on, lid off, air box off you name it i tryed every way

[thump4863]

clean your carb again - you never know you may have missed something - jake all jets out and blow those - is your float sticking? It sounds like its a carb problem.

[thump4863]

also drain your gas tank and go get some new fresh gas - maybe some bad gas

[440challenger]

Maybe lean...
try it with the air filter back on...
Then place the air box lid back on see if that helps!!
Keep us up dated.:

Well you hit the nail right on the head sir. I feel like an idiot but the happiest idiot in the world right now. 2 days ago i had the 450 air box and tube in my quad with the lid ON. Yesterday i put in my 400ex air box and tube back in becuase it doesnt hit the shock and seat like the 450 one did ,with the LID OFF. In between doing that i was doing a bazillion other things. It never poped into my mind that the lid would cause THAT big of a difference!!

But i guess in these 20 and below tempatures it is,especially with stock jetting. Im guessing i am SUPER lean.

I took the main jet out and it was a 118,so i put a 125 in.Big difference but it still has a flat spot in the midrange to top end. Does anyone know where i could find the stock jetting for an 2004 trx 450r and the reccomend baseline for sea level in stock form?

The old honda cr mauals used to have a jetting table for temp and altitude. Do the newer quad manuals have that inside them?


AGAIN I CANT SAY THANK YOU ENOUGH! That was a big RELIEF!! :D

[ss440ex]

SWEEEEEETTT!!!:D :D :D

[ricks450]

if it is all stock, jets, exhaust spark arrester in, everything. and you take the aibox lid off, it will do what yours is doing. my bike did the samething one day when i was playing with mine. just to see. put the filter back on, airbox lid on and spark arrester back in if have that out. and see if it changes. if it seems to better but not where it should, go up on your main jet. it sounds lean to me. check your spark with a spark tester if you have one that will get in there. to see if your coil is braking down.

[ricks450]

Originally posted by ricks450
if it is all stock, jets, exhaust spark arrester in, everything. and you take the aibox lid off, it will do what yours is doing. my bike did the samething one day when i was playing with mine. just to see. put the filter back on, airbox lid on and spark arrester back in if have that out. and see if it changes. if it seems to better but not where it should, go up on your main jet. it sounds lean to me. check your spark with a spark tester if you have one that will get in there. to see if your coil is braking down. im late

[440challenger]

I have the stock exhaust but the insert is removed. If i take the lid off should i go up to say a 180 main? stock pilot and clip position?

[rap169]

180 is correct

[450 Racer R]

i'd get the hrc needle and run that on the third clip also

[komatsu kid]

this happend to me, the clip wore out on the needle,had to get new needle and clip