Blue Exhaust flames?

[tye101]

hi, i need to know if my quad is running to rich, or to lean,, all the info of my mods is at the bottom of my sig,,,

My header pipe glows red hot,, and after u gun the engine,, sometimes it backfires blue flames out the exhaust,, is this a problem?, or just part of it ?,, i rejetted it after i put on the full exhaust,, but not after i added the intake,,,

Thanks

[ak_stick]

I'm no expert, but blue flames would indicate that you have alot of unburned gas in your exhaust, hence your WAY rich.

[400eXr1d3rZ]

but redhot header means your quad is running super hot, thus lean? I have a thread about this somewhere but its about a warrior.


http://www.exriders.com/vbb/showthread.php?s=&threadid=246898



GPracer2000 quote!:

My guess is his pilot circuit is too lean. Flames coming out of the exhaust doesn't necessarily mean he's too rich. Flames shooting from the exhaust can be caused by being too rich OR to lean. I would think a blue flame (as oppose to yellow/orange) suggests a lean condition. Rich mixtures burn cooler (yellow/orange flames) while lean or stoich mixtures burn hotter (blue flames). But just the fact that this condition developed after adding a slip-on makes a lean condition by far the most likely.

It seems like a way too lean mixture would consume every last bit of fuel. That (incorrect) assumption causes confusion and begs the question of how a lean air/fuel mixture can create flames shooting from the exhaust. The answer: Lean mixtures burn unreliably. This causes pockets of air/fuel mixture in the combustion chamber to occasionally not burn at all. These unburned mixtures get passed out of the engine into the exhaust. As unburned fuel passes through the exhaust it will occasionally find conditions that allow it to ignite and the result is flames shooting from the exhaust.

Typically, the unburned fuel from lean missfires ignites in the headers much closer to the engine and that's what causes the "lean pop" that is so familiar. But sometimes (depending on exhaust design, the quantity of unburned fuel, and other factors) it doesn't ignite until the moment it exits the exhaust.

[ak_stick]

if hes having combustion outside of the cyl he could well be running rich, and just the combo of external uncontroled combustion and exhaust gas temp making the header hot.

Or atleast thats what I understand, I could well be wrong.

Edit, posted just after you posted that.

That very well could be it, I dont have a very vast base of quad sized engine experince to draw on. Most of mine is turbine and higher end gas engines where shooting flames = too much fuel.

[DieselBoy]

blue flames indicate an extremely hot flame. fuel dumping in your exhaust?

[Iliketogofast]

It's either lean or it's out of time. If it were rich enough to dump that much fuel into the exhaust, it would be fouling plugs, and that is if it would even run which I doubt.

I'm leaning toward the timing, seeing as how my buddy's 400EX did the same thing just yesterday. There is some sort of key in the flywheel that, when given too much clearance, can cause the timing chain to jump.

I'm not sure of the specifics on timing and such because I never had such a problem on my EX, but I thought I'd throw that idea out for you.

[tye101]

thanks, i know it's not the timing,, i have never cracked the case to throw it off,, i am almost sure after talking to you guys, that it is running lean.... i have a 3 yr warrenty, so the dealer will have to do it, so it won't void it .

[GPracer2500]

Jetting a quad yourself won't void your warranty. Now, if you rejet and screw it up so bad that your engine melts--well, THAT would cause a dealer to reject covering repairs under warranty. But just rejetting yourself doesn't automatically void the warranty.

[tye101]

it does at the dealership i use

[GPracer2500]

Originally posted by tye101
it does at the dealership i use

The dealership doesn't get to decide what does or does not void a warranty. They'd like you to think it's they're call, but it's not. Federal law and the cause of the failure determines when a warranty doesn't cover something.

Research the Magnuson-Moss Warranty Act (that's the law that governs written warranties) and consult the manufacture yourself before you let your stealership steam-roll you....

[DieselBoy]

dealer's will lie through their teeth about denying warrenty work, but a quick call to the manufacturers head office will surely straighten their attitude out.

[tye101]

it doesn't matter,, i dom't really wanna rejet it my self,,

[400eXr1d3rZ]

well dont bring it to the dealer, you will be overcharged.