major backfireing

[vinnytobasco]

Hey everyone, I recently took my quad apart to throw on new parts,then reassembled it and went rideing.Had a great time rideing, even though by the end of the day it progressivly started to pop lightly during deceliration.The day of rideing was cut short because of me wrecking and bending a tie rod.Then today I straigten my tie rod out, go over the whole quad, everything looks good soo i put it together.Push her outside, fire her up and shes running a little diffrently.Befor it wouldent idle with the choke on , and it would idle good without the choke cold.Today she wanted to idle really high with the choke, and then after warming it up it wants to idle really choppy and die after about 15 seconds of no throttle.I gave it a little throttle and it spits a blue flame out the exhaust after wide open throttle in neutral wile comeing to an idle.I adjusted the air fuel screw outwards from flush, and it leaks gas out of the over flow.Anybody have any idea whats wrong with it ?Any help if much appreciated it's snowy and i want to tear it up soon! Thanks in advance!

[Scro]

Did you install anything that would alter the air/fuel mixture, like the exhaust or intake? The screw you adjusted on the carb was probably the bowl drain instead of the air/fuel screw.

[vinnytobasco]

No i did not, I did push the snorkle into the airbox a little better because it wasen't flush with the air box.Just to clearify by the snokle i mean the clear air intake thing.Also is the carb bowl drain, the one that is faceing outward towards the magneto side ?Another thing is, on the exhaust side there is a hoseline that comes down from the carb with a regular ( flathead ) screw in it, it has a mount attatched to it but it is just hanging there stuck to my starter , any idea what that is , or if it has anything to do with my problem ? The quad has an hmf pipe and uni airfilter it was like that when i got it, any further mods are unknown.

[Scro]

I believe the air/fuel screw is on the bottom of the 400ex carb. The one on the side definitely sounds like the bowl drain.

[vinnytobasco]

ok should I just start off with adjusting that?Dose is sound like its running lean or rich? My dad said it seems like its running rich but, he dosen't help me much anymore sence i'v been working on my own stuff.

[vinnytobasco]

bump

[sneaky11]

Probably need idle ajdustment, with your a/f screw

http://s759.photobucket.com/albums/xx239/rocky_mtn_honda/TRX400EX%20Manual%20Pages/?action=view&current=carbadjustment.jpg

[vinnytobasco]

Anyone else have any idea what it could be, I replaced the spark plug today the old one was about dead.I thought it was going to help and it did nothing.Same thing, but now it idles in neutral, but it has a surging idle, very ruff and uneven.Any help would be great.

[BenHonda400ex]

Which way did you turn the air fuel screw? Clockwise or counter clockwise?

[vinnytobasco]

I turned it clockwise ....

[coreo5]

go buy a new plug...start it and take it straight to wot and kill it...pull the plug and tell us what the plug looks like. it sounds to me like your running really lean. if you rev it up are you seeing any black smoke coming from the exhaust?

[BenHonda400ex]

Originally posted by vinnytobasco
I turned it clockwise .... I think you're suppose to turn in counterclockwise.

[vinnytobasco]

Hmm ok so I should try adjusting it counter clockwise and see if it helps.Also it is blowing puffs of black smoke on start up and, I diden't wanna damage anything so once i seen that i killed it.I haven't ridden it sence it started backfireing, in fear of frying my rings.

[vinnytobasco]

Also I already did the wot with a new plug and pulled it, it was brown / tanish , which leads me to belive my main jet is good .And my problem is it's lean on the pilot jet.I'm going to adjust my air fuel screw, is there a special tool to do it ?I can never seem to get to it at all.

[MisterGraphic]

Did you change the header gaskets when you re-installed the header ?
Mine was backfiring on Decel like crazy because of an exhaust leak.

[vinnytobasco]

I personally never removed the header sense i had the quad.I assume that it was because it has a fresh rebuild and new exhaust studs and nuts, I'll check the connection when i get home.It doesn't seem loose but it may.

[MisterGraphic]

Yeah mine seemed on very tight (didn't
move and I couldn't feel the leak with
my hands either)

It was a small leak but whenever you
decel it creates a vacuum in the motor
and the cold air from outside goes in the
head and comes out of the muffler
creating a backfire.

May be worth checking since it only does
it on decel. The gaskets are 2.99$ each
at honda, Replaced mine in 15 minutes :)

[BenHonda400ex]

Originally posted by MisterGraphic
Yeah mine seemed on very tight (didn't
move and I couldn't feel the leak with
my hands either)

It was a small leak but whenever you
decel it creates a vacuum in the motor
and the cold air from outside goes in the
head and comes out of the muffler
creating a backfire.

May be worth checking since it only does
it on decel. The gaskets are 2.99$ each
at honda, Replaced mine in 15 minutes :) Do they usually come out with the stock exhaust because I didn't see anything like that when I changed it out

[MisterGraphic]

It's about 1" in diameter, made of copper
and it's hollow. (Like a small donut)

They stick on the motor head and you
have to pry them out carefully with a
screwdriver. (Copper Crush Gaskets)

Here's a picture of something similar:
http://www.aircraftspruce.ca/catalog/graphics/an900b.png

[vinnytobasco]

Thanks mistergraphics, thats something I never would have though of i'm going to order a set.For that cheap it wouldent hurt to replace even if that isen't the problem.

[MisterGraphic]

No problem,
Hopefully it works for you.

Keep us update of what the problem was
and how it was fixed.

[josh25ex]

its a leak in the header at the copper gaskets that you have to replace everytime you take the header off. it could also be where there header meats the muffler cheap 3 dollar fix and maybe some tuning.

[josh25ex]

easy way to get them out heat them up alittle with a torch not long just like 20 seconds, use a flat head and pop them off. tryed with out heat they werent moving

[vinnytobasco]

Ordered a set last night, I'll keep you guys posted on when I get them and how things turn out.Hopefully its just a 3 dollar fix , but just incase it isen't i'm looking for a cheap dyno jet kit.Any one have any experience with the sigma raceing jets kits on ebay?

[vinnytobasco]

mr.graphics, When you installed the copper exhaust crush gaskets did you press the gasket in first, then bolt on the head pipe.Or did you just kind of set it in there then dolt on the header.I'm haveing trouble installing it , any help would be great !

[CJM]

I put them in there then bolt the header up as evenly as I can.

[vinnytobasco]

Only problem is i can only get a stud on the one side of the mount , but there isen't enuff room to get the nut on the 2 other studs that is still in the cylinder.Just to clearify , one each manifold , one whole stud came out of the cylinder and one nut just came of on each side.Not sure if that is normal.Also if my old gasket was all flattened out and uneven , dose that mean it's bad? I can put pictures up if needed.

[CJM]

So your saying the studs pulled out of the head? Thats VERY bad. I had a similar situation where the stud snapped, 2 pulled out replacements later and if this last one doesnt hold (by now its a 10mm diameter bolt!) Im getting the hole tig welded and gonna drill and retap it to the proper size.

Try tapping it for a larger size and cutting a bolt down, not much else you can do but helicoil, but as Ive said before I have not had good luck with helicoiling these soft aluminum top ends.

The gaskets crush so it was doing its job then. Might want to check and see if you have 1 gasket in there or more-I thought I yanked them all out last time-turns out the carbon hid the ones I musta never pulled.

[vinnytobasco]

I diden't pull it or stripp the aluminum threads , just the stud and nut came out instead of just the nut .It threads right back in easly.I'll check for more gaskets in there but i don't feel anymore left in there.No you got me freaking out about the studs lol ....

[CJM]

Ah ok I thought you meant it pulled out. Good it didnt.

Get a new stud, that ones trash. Take the stud and some nuts that are the right size (I think it might be M10x1.0) and put 2 nuts on there and tighten them up so they cant move. What you want to do is but the nuts up against eachother and tighten them so they work as a solid place to wrench on.

Then tighten the outer nut to run the stud home.

Also take notice the stud has 2 different ends of thread-ones longer than the other-I cannot recall which side goes in the head but the rest of the studs can show you.

[MisterGraphic]

Good information CJM,
I couldn't have explained it better.

I did the same thing with the nuts,
Place crush gaskets, place header and
finger tighten bolts, then tighten them
progressively in a criss-cross pattern to
make sure the gasket is crushed evenly
into place.

:)

[vinnytobasco]

Thanks guys you answered all my questions and with great detail.I will give it a go when i get home from school , and let you guys know if it helped with my problem......