Jetting - Sputtering Top End

4 replies to this topic
  • Herkypilot

Posted October 28, 2001 - 02:38 PM


I've read many posts on jetting and I can't find one that relates to my problem. At about 3/4 - Full throttle the power drops off and the engine sputters until I back off on the throttle. The bike starts fine, good quick throttle response throughout except top end. My current settings on my '00 400WR are:
-Throttle stop trimmed
-Baffle removed
-Airbox snorkel removed
-Pilot screw 1 1/2 turns
-PJ # 45
-MJ # 172
-Stock Jet needle (OBDRS) on clip #2

All other parts stock. Would this sputtering/power fall-off be an indication of a rich or lean problem?

Thanks in advance.

[ October 28, 2001: Message edited by: Herkypilot ]

[ October 28, 2001: Message edited by: Herkypilot ]

  • James_Dean

Posted October 28, 2001 - 07:44 PM


Probably rich, but the main jet size is good unless you're at high altitude.

Make sure that air filter oil or dirt have not clogged the Main air jet, remove the carb and clean the passages. There are 2 air jets on the intake side of the carb, pilot and main air jets. Be sure the air filter is clean and not over oiled also.

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  • jamracing

Posted October 29, 2001 - 06:34 AM


Did you try to put the needle back to stock, and drop the pilot to 170? :)

  • Herkypilot

Posted October 29, 2001 - 11:10 AM


I'll give the carb a good once over to make sure all is in order. I will probably try going down to a 170 MJ also. Just to clarify, I'm operating from the 400 to 700 foot range. I'll let you all know how it goes. Thanks. :)


Posted October 29, 2001 - 06:36 PM


With the stock exhust the main jet seems a bit big.


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