P f f f f t t sound on decel

2 replies to this topic
  • Pooley

Posted August 26, 2003 - 03:31 PM


I'm trying to get my settings dialed in and was wondering what the pfftt sound on decel at slow speeds is an indication of. The sound is not long, about the duration of a bang or pop without any of the percussiveness. I've been doing tests in my backyard trying to loft the wheel at low speeds without the off idle bog. I've got an 01 WR timed, airbox lid removed, Vortip and BK mod at 0.5 sec.

I started today at settings found to work well for tctrailrider and are as follows:
JD red 5, 165 MJ, 200 MAJ, 42 PJ, 75 PAJ, 65 SJ, Fuel screw 1.5, elevation about 700 ft, temp 80degF, 75% humidity, new plug and clean air filter (properly oiled). Got siginificant bog off idle and was like bad turbo lag. Went in to 1.0 on the fuel screw and was about the same.

Second try was the same except for dropping the needle to clip 4 with fuel screw at 1.5. Bog seemed a little better. Went to fuel screw 1.0 and bog was less but still noticable, turbo lag feeling still there but less. Went to 3/4 fuel screw and was a little better but now with the pfffftt sound. Went down to 1/2 fuel screw and the sound was a little worse without much gain off idle.

I plan on trying JD Red on #3 tomorrow to see how it goes.

Does this sound like I may need a smaller pilot jet or just wait to see how #3 works?


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  • tctrailrider

Posted August 26, 2003 - 04:05 PM


Starting tomorrow the heat wave is gone. The 10 day has highs in the 70,s. Try the Blue 4 and see what happens. Red 5 worked great for me when in the 80,s. The Blue 4 I tested at about 70 and it was great, lost a little when it got hot. I put the Blue 4 back in tonight and will test it shortly, waiting for the temp to drop a little. Will let you know. As for the strange sound you have on decel, no idea, haven't experienced that before.

  • tctrailrider

Posted August 26, 2003 - 06:51 PM


Tonight I tested the Blue 4 at 75 degrees. Had to get it real warm before the 1/4 to 1/2 throttle miss went away. It was just a little rich. Just a little cooler and it will be perfect. The Red 5 is leaner that Blue 4 all through it. If you try Red 4 it should give you a good indication of the direction you need to go. You may also want to check your squirt duration to make sure it has not changed since the BK mod. Also check the FS at 2 and 2.5. Happy hunting.


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