fmf exhaust

4 replies to this topic
  • zook350

Posted February 13, 2007 - 10:04 PM


i have a 00xr650r with full fmf exhaust system. header, power bomb, and Q muffler. i've noticed that when when the engine is cold with the choke on the header will glow cherry red, is this due to header pipe material. uncorked,175,65s,needle in third position. any body else have this exhaust or experienced a similar condition?

  • Thumpage

Posted February 13, 2007 - 11:46 PM


The first clue might be: Unless you are at high elevation, the 65S pilot jet is just too lean. The bike needs at least a 68s pilot jet at lower to moderate elevations especially with a full exhaust system. Then of course properly dialing in the fuel screw after the change.
Because of the possible lean condition at idle, that is why the header might glow too much because it is running hot,:censored:. Even when this is corrected, you may notice that the header can glow a bit at times especially in your garage out of direct sunlight. Stainless steel shows more of the glow than the stock black header.

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  • zook350

Posted February 14, 2007 - 08:16 AM


a lot of my riding is a 4500 ft and up to about 8000, will a 68s be to big for this elevation? i went to the honda dealer and the number on the internet for the 68s is just a 68, how do you get the s pilot?

  • Thumpage

Posted February 14, 2007 - 04:24 PM


That is the oldest confusion at Honda shops, :censored: . What many parts guys don't know or can't tell you is that the pilot jets listed on the XR650R carb parts screen are the actual 68s pilot jets. What they are, is Honda specific versions of the standard keihin 68 pilot jet. The difference is that the air emulsion holes along the fuel tube are smaller on the 68s. Because of this, they act somewhat different at moments when deccelerating and at idle, given the same pilot = fuel screw adjustment. So, to get the actual 68s, just go ahead and order from the XR650R carbs parts menu. Any pilot jet they can give you over the counter from their jet bin will not be the 68"s". They will be standard 68 keihin jets. These do work but as I say they can make the carburation 'act' slightly different.

O.K., regarding the pilot jet size: You need to go through the proper fuel screw adjustment procedure to check which pilot you should have. If the pilot jet falls between 1.5-2 turns out after the tuning procedure, it is the correct size. If it has to be turned past 2 turns out than you will need to step up a size to the 68s. Even at your generally higher elevation, I think you may need the 68s since you have a full exhaust system. But again, check to be sure. Here is a quick and easy quote of the procedure from a great XR650R website and it's carburation contributer:

"Make sure your engine is fully warmed up and set the pilot screw to 1.5 turns out. Then with the 68s installed, turn the pilot screw clockwise until the idle slows. Then turn the pilot screw counterclockwise until the idle slows again. Make a mental note of how many turns you made in between the low idle points. Then turn the pilot screw half way between the low idle points to finish the adjustment. If you turn the adjuster counterclockwise and the idle doesn't drop down, then you need a larger pilot jet. If you turn the pilot screw clockwise and the idle doesn't drop down, then you need a smaller pilot jet. After adjusting your pilot circuit, re-adjust your idle speed if necessary."


  • zook350

Posted February 14, 2007 - 09:21 PM


thanks a lot for the advice, when it is warm, turning the screw counter clockwise will not drop the idle. i am going to order the correct pilot.

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