What Causes This ??? Flame out exhaust (YFZ)

[Quad18star]

Alright , well today I went and started up my YFZ over at my parents place , and as I'm letting it idle , I give it a shot of gas and a flame shoots out the exhaust . It's been pretty hot lately ... like above average temps (30 celcius or 80+ Fehrenheiht) .

Is this a jetting issue ( my guess) . I'm jetted at what Sparks recommends which is 178 main , 42 or 45 pilot ( i think) and 2 1/2 turns on the air screw .Is it jetted too rich , or could it be lean ?? I didn't have time to check the spark plug today to see how it was running . I need help before I do any kind of damage to the engine .

Any suggestions are appreciated . Thanks

[jak1389]

yea sounds like a jetting problem, and i think its probably going to be way too lean.

[wilkin250r]

I'm not so sure on the jetting, but I certainly want to see a picture or video! :devil:

[bwamos]

What color is the flame?

You're probably lean.

Turn on the choke a little (if you havent taken it off), and try it again.. if it fixes it your too lean.

Yellow flame is rich
Blue flame is lean (most common)

Unless you have a spark arestor.. then it's always yellow.

[Quad18star]

Its a yellow flame and shoots out about a foot behind the exhaust !!!!:confused:

[MadMax27]

As it gets hotter outside, it gets richer, right? Maybe adjust your air/fuel screw, or swap a smaller pilot in. My HMF full runs great with a 42, any bigger and it would fould bad.

[03400EX_Nacs]

i was at some races the other night and since i am not racing i was just cruising around on my yfz and after letting it set for a little while pulled mine into our trailer and when i cut it off i didnt see the flame but our entire trailer lit up with a little poof of a flame so it had to be big and my dad even noticed and ask about it. so could this be my jetting? because also when its even warms if i jab the gas about 3/4 throttle real fast it goes... blah and if i held it , it would die... (this is at an idle).............. BTW i dont mean to cut in on your post but i thought it was a little on topic and didnt want to make a new one sry :o

[Quad18star]

Originally posted by MadMax27
As it gets hotter outside, it gets richer, right? Maybe adjust your air/fuel screw, or swap a smaller pilot in. My HMF full runs great with a 42, any bigger and it would fould bad.

Thats what I was thinking ... but figured I'd ask the question . I'm almost positive I have a 42 pilot in it ( it's the jet that comes with the Sparks jet Kit !?!?!)

I guess I'll have to take the plug out and see how it is , then start playing with the air fuel screw . Keep your fingers crossed that I don't blow anything up inside the motor !!!!

[Quad18star]

Here's my jetting ....

178 main , 45 Pilot , NCVQ needle on 4th clip , 2 1/2 turns on fuel screw .

[mattonln]

it sounds like your rich actually... my TRX does that when its really hot outside and the engine is cold. It loads up and backfires basically... i just deal with it because its usually not that hot here... good luck man, i usually just adjust my air/fuel screw if that happens and it will basically take care of it...

[bonified5]

I wan tmine to throw flames....how do I get it to do that with no harm

[z400roosteR]

Maybe if you ask 30 more times someone will respond.:rolleyes:

[DeerNuts]

Originally posted by bonified5
I wan tmine to throw flames....how do I get it to do that with no harm

dude why did you ruin Greg's thread. you want it to shoot flames blow the damn thing up.

[bwamos]

Originally posted by bonified5
I wan tmine to throw flames....how do I get it to do that with no harm

Mount a spark plug on your exhaust tip, duh!. Past the spark arestor so the flame doesnt go back into your header and blow it off.. lol.

[z400roosteR]

with mounting a spark plug wouldn't you need to run like raw gas through to the exhuast?

[Quad18star]

Well I got the answer to my question . Today was a little cooler outside , so I scooted over to my parents palce and fired it up . No foot long flame shooting out the exhaust today ... only a tiny flame inside the pipe on de-accel. Putting my knowledge to work , I figured it must be running too rich ( the bike performed well when the temps were in the 60s ( running leaner) .

On a side note .... the old man took it down the street for a little ride and was lifting the front end in all gears ... not too abd for a 56 year old guy . Way to Go dad !!!! :D

[bonified5]

O shoot guys sorry didnt mean to do that ......i kept pushin the post buttion...ill get rid of them.

[400exBro]

Greg is your header stainless steel??
i have been told that if your header turns a nice shade of blue after the exhaust manifold you are probably to lean...
i have been having problems with mine, i have the stainless header as well for the sparks exhuast, my head pipe is a nice shade of purple blue colour.... I can't get it to go away... there is a little bit of poping on decl, but other then that is runs awsome all the way throw...
another question, after having it sit for a while and you start it up and give it a bit of gas, does a bit of black smoke come out of the exhaust?? it only happens when the engine is cold and has been sitting for a while( happens twice then goes away)??

[Quad18star]

Originally posted by 400exBro
Greg is your header stainless steel??
i have been told that if your header turns a nice shade of blue after the exhaust manifold you are probably to lean...
i have been having problems with mine, i have the stainless header as well for the sparks exhuast, my head pipe is a nice shade of purple blue colour.... I can't get it to go away... there is a little bit of poping on decl, but other then that is runs awsome all the way throw...
another question, after having it sit for a while and you start it up and give it a bit of gas, does a bit of black smoke come out of the exhaust?? it only happens when the engine is cold and has been sitting for a while( happens twice then goes away)??

Yeah , there's a bit of black smoke when I first start it up when it's been sitting for a while , but then it goes away . I do have the stainless header and the pipe does turn blue . I don't think it would be too lean since I'm running a 178 main ???!!! Like I had mentioned ... it only did it when the temps were really hot the other day , and the day after when the temps had dropped about 10 degrees , I only had a little flame inside the exhaust on de-accel . I'm gunna have to pull the tank off and check the plug but I've been too lazy . :ermm:

[muddy400EX]

mine shot out a flame once when the engine was cold and it was hot outside. i would say that yours is prolly to rich cuz mine is way to rich, it has a black plug. if you have a spark arrester in it then it prolly wont shoot out flames