more jetting ?'s sorry



6 replies to this topic
  • JT_in_WP

Posted April 18, 2001 - 07:25 PM

#1

i live and ride at around 8900 ft. my bike had stock jetting and was fouling plugs often so i droped the main jet to a 160 from a 165, the bike seemed to have more power at first although less top end, today i got plates for it and took it around town and it ran worse than yesterday on the trails, it backfired every time i let off the gas and there was a hugeflat spot at half throttle, it felt like it was sputtering and uneven, i checked the plug and it was still black although not as much right on the electrode (if thats the name of the part where you gap), any sugestions would be much apperciated.
p.s. 01 wr426 ab lid off baffle off, throttle stop shaved.
john

  • James_Dean

Posted April 18, 2001 - 08:29 PM

#2

John,

The low speed jetting is controlled with the pilot circuit and needle. Adjust the pilot screw in (leaner) or out (richer) checking response. Also consider moving the needle 1 clip higher.

The main jet is adjusted for 3/4 to full throttle jetting.

James

[This message has been edited by James Dean (edited 04-19-2001).]

  • JT_in_WP

Posted April 19, 2001 - 08:45 PM

#3

james,
today i took the carb out and dropped the needle to the #3 position, or one grove higher than stock. and tested it with the 160 as well as the 165 main. also i turned the pilot screw approx 1/2 turn in. i ended up with the 160 main as top end was better. for a while the bike was running great at all throttle positions, after a bit longer road ride the bike seemed to break up a bit and low and middle end seemed weak. also it started backfireing alot. i checked the plug and it was dry and darker gray/copper. does the bike take some time to realize the full effects of carb adjustments or is it emediate.
thanks
john

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  • James_Dean

Posted April 19, 2001 - 09:05 PM

#4

Try a few different pilot screw settings. You may need to back it out again. Turning it out will be richer at idle, turning in will be leaner. How many turns out from full in is it now?

A lean pilot circuit usually pops a little on deceleration. The pilot screw can be turned out as many as 3 turns, indicating a bigger pilot jet is called for.

James

[This message has been edited by James Dean (edited 04-20-2001).]

  • JT_in_WP

Posted April 19, 2001 - 09:14 PM

#5

james,
i would say the pilot screw is at 1 to 1 1/8 turn out based on the manuel specs and the fact that everthing else on my bike was set up stock even though they told me the bike was jetted for my elevation. tomorrow i will turn screw in all the way and count rotations. it just seemed to go from way to rich to too lean in minimum adjustments. i say to lean because of the plug color but it is not gray it is darker than that.
anyone else running at 9000 or so with low humidity and temps in the 60s to 80s.
thanks
john

  • Taffy

Posted April 19, 2001 - 10:24 PM

#6

jd

will have a word about the APJ.

james...

Taffy

  • James_Dean

Posted April 20, 2001 - 05:20 AM

#7

The accelerator pump jet (APJ) on the FCR carb was designed to feed as many as 4 carbs at one time. There may be too much fuel squirting from it on acceleration. On the other hand, when it's not working at all there can be a bog and loud backfiring.

It would be best to stick with adjusting the pilot screw setting at this point and check the pump operation next. Make sure its not clogged or that the spring loaded rod is not binding or loose/disconnected (under the black cover on the side of the carb). The pump flow can be reduced with a P-38 Lightning from Factory R&D, but other WR owners have been successful in jetting at your altitude without it.

James

[This message has been edited by James Dean (edited 04-20-2001).]




 
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