will a header/pipe exhaust leak make an engine run very lean?

4 replies to this topic
  • Shane_Bettin

Posted July 01, 2004 - 01:39 PM


ive been having problems with my bike running really lean. theres is a leak where the header connects to the pipe, would that be the the problem. it was running perfect before but since i put as new pipe on its been real lean. i did go up a size with the main, 175-178. im thinkin of usen some kind of shrink wrap or somthin and maybe some gasket maker/sealant. any ideas?

  • Dolce_Grappa

Posted July 01, 2004 - 02:11 PM


Yes an exhaust leak will cause a lean condition; you can use Chamber Seal or Permatex, Ultra Black. Chamber Seal worked fine on the 2-smoke, but just melted from the exhaust temps from my 4-stroke.
NAPA will have the Ultra Black; you’ll have to let it cure a little prior to sliding on the silencer.
Let us know how it works for, ya!

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  • Bobby_Holeshot

Posted July 02, 2004 - 06:57 AM


MXA Mag has a great article about how pipes work on MX bikes and talk about the importance of tight joints and leaks.

  • Shane_Bettin

Posted July 02, 2004 - 09:09 AM


does it talk about it on the web site, or which issue is it in?

  • sirthumpalot

Posted July 02, 2004 - 12:17 PM


You say it's lean, but where (at what throttle opening(s)) is it lean? For very small throttle openings (idle to about 1/4) play with the fuel screw and pilot jet. For mid openings (about 1/4-3/4) the needle and clip position will have a significant effect, and for over 3/4 the main jet will have the most effect. I'm not a jetting guru, but this is the basic way it works, hope this helps.

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