Flames coming out the exhaust????



5 replies to this topic
  • motoman393

Posted January 12, 2001 - 05:00 PM

#1

I recently rejetted my 01' 426 to 168 main and 48 pilot 1.5 turns on fuel screw. This thing runs SOOO much better above 1/3 throttle but down low it has a tiny stumble (pilot circuit??)! Whenever I let off the gas it sometimes (1 out of 4 strokes) it shoots a 3-4 inch flame out the back of the muffler (looks cool but I know its not right)! I had the 42 pilot at 2 1/3 and it ran ok but im thinking I need to put the screw at 1 - 1 1/4 on the 48 pilot jet! If yall have had this happen or could give me any suggestions please write back i would appreciate it! Thanks,

Garrett

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I get my kicks on a 2001' YZ426!
Friendswood, TX

  • dirtdad

Posted January 13, 2001 - 04:59 AM

#2

Garrett, Did it backfire along with the flame or just a flame. Either way I'm guessing your bike is too rich somewhere. I would try going slightly leaner on the fuel screw or pilot (one at a time, easiest first) and see if that solves the problem. I always run into problems working on carbs (car or bike) when I try more than one change at a time. Hope this helps.

[This message has been edited by dirtdad (edited 01-13-2001).]

[This message has been edited by dirtdad (edited 01-13-2001).]

  • motoman393

Posted January 13, 2001 - 05:57 AM

#3

it backfires too...thanks for the suggestion I will lean the fuel screw 1/4 or 1/2 turn and i will see if this works! Thanks,

Garrett

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I get my kicks on a 2001' YZ426!
Friendswood, TX

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  • dirtdad

Posted January 13, 2001 - 07:08 AM

#4

Garrett, If my original suggestion doesn't fix your problem I will offer another. At the risk of sounding like a woman (no offense to members of that persuasion) and doing a 180. A lean condition will also cause your bike to back fire. I'll quote from the latest Ask Dr. Dirt in Dirt Rider "A small, popping backfire noise in the exhaust whenever you let off the throttle is caused by a lean pilot mixture or slow-jet setting. The mixture in the combustion chamber is so lean that it fails to burn completely, leaving pockets of unburned fuel to escape into the exhaust. These small pockets mingle with other pockets of unburned fuel and ignite intermittently."
The article suggests that maybe the owner of the bike in question possibly is forgetting to push the hot-start button back in. I'm sure you're not doing this since you've had the bike some time. It also suggests that the first adjustment should be to richen the fuel screw in half turn increments. If this doesn't totally eliminate the popping, richen the pilot jet one size. Since you had originally mentioned that you had already gone richer on both of these, that's why I suggested the rich condition in one of the two possibly being your problem. I'm assuming you didn't experience a backfire before you made the original adjustments. I apolgize for the long winded response, but I hope this helps.

[This message has been edited by dirtdad (edited 01-13-2001).]

  • Taffy

Posted January 14, 2001 - 03:01 PM

#5

motoman
go back to at least a 45 or even the 42. what the hell are you doing pissing about wih a bike that ran well from the crate?

how can 42 become 48. remember that this jet affects off idle. you can start the bike ok but does it RUN ok?

go back, juice it up on the pilot screw & don't change the jet.

Taffy

[This message has been edited by Taffy (edited 01-14-2001).]

  • motoman393

Posted January 14, 2001 - 08:21 PM

#6

I was thinking the same thing taffy...what about the main jet (168 or 162)??? Thanks,

Garrett

------------------
I get my kicks on a 2001' YZ426!
Friendswood, TX





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