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03 KTM 525sx SM popping off throttle

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hi guys, picked up this 2003 525sx Supermoto 2 weeks ago as a new toy. It's been supermoto'd since new and never been offroad, and it's been 6spd converted :D so that's cool. well it was having a hell of a time hot starting (kick start only is a pita but w/e). i put a JD jet kit in it with a new needle, upjetted from 170 --> 182 and a O ring on the accelerator pump. also the a/f screw was out 3 turns. i started at 1.5 and now im at 2 out.
she's running Much better now, both Hot and Cold starts but when letting off the throttle she pops A LOT. is that normal for this bike ? w/o a wideband or constantly plug checking idk how rich or lean she's running

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Deceleration popping is due to and AIR LEAK or a LEAN CONDITION.

The most common air leaks, in order:

  1. Header crush washer is leaking/worn out. Everytime you drop the bike and bump the header, it will start leaking.
  2. Mid pipe seal: re-attach with high-temp silicone seal
  3. fuel screw o-ring is worn out. Replace
  4. hot start plunger is leaking, due to corrosion (clean, lube, replace) or a cracked hot start nut releasing the required tension on the plunger
  5. cracked/leaking carb boot
  6. Muffler packing worn out, causing un-balanced exhaust pressure.

Most common lean condition causes, in order:

  1. Someone 'rejetted' the bike. There is no reason to EVER change the jetting on a well running bike unless you significantly change your air density or change your intake or exhaust tuning. JD Jetting has an easy fix, but it will cost you $80 for the instructions and $15 worth of jets.  
  2. Fuel screw is incorrectly adjusted and/or the pilot jet is the wrong size. This is a constant source of confusion. You adjust the fuel screw for IDLE SPEED. Starting with the fuel screw at 1 turn out, a hot motor, and the lowest possible idle, you turn the fuel screw OUT until the idle starts rising. Stop when it stops rising. If the idle speed is correct, you are done. If it is too high, lower it, and try again. If your fuel screw ends up being at between 1 and 2 turns out, you have the correct size pilot jet. If you have less turns, the pilot jet is TOO BIG. Go down one step. If it is more than 2 turns, it is TOO SMALL. Go up one step.  IF YOU TRY AND ADJUST THE FUEL SCREW WITH A PILOT JET THAT IS THE WRONG SIZE, YOU WILL GET HANGING IDLE, OR YOU WILL GET A FLAT SPOT.
  3. Intake valves that do not seat except when very hot. The symptom for this is also difficulty to start cold (assuming the carb is set up right)

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awesome, i'll check everything you listed. much thanks!

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