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Flat spot

This is a discussion on Flat spot within the Yamaha YFM660R Raptor (2001-2005) forums, part of the Performance /Technical category; First off thanks again for all the help when it wouldn't start, it did turn out to be the stator!! The other problem I'm having ...


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Old 03-16-2010, 11:03 PM   #1
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First off thanks again for all the help when it wouldn't start, it did turn out to be the stator!!

The other problem I'm having is just above idle it sputters with no power, how ever it idles fine and runs fine above that point in the throttle. This is a real pain when climbing a rocky hill, but it does it anytime even on level ground just in that RPM.

This rappy is basically stock with the air box lid off, the baffle out and has been rejetted for this altitude. The plug is burning a light tan color.
Thanks again for your help!!!!
Steve
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Old 03-17-2010, 12:16 PM   #2
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Idle and low RPM fuel mixture is controlled by the pilot jet and the pliot fuel fuel screw. I would first try to adjust the pilot screws out 1/2 turn and then 1 turn. If you have to adjust much more than that you should step up a size on the pilot jets.

The pilot fuel circuit is the first to plug or gum up as the passages are so small. You might need a good carb cleaning too.
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Old 03-17-2010, 02:26 PM   #3
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Thanks! I should have mentioned on the pilot jets stock is a 22.5 I am currently running a 25 and have also tried 27's too. The air screw is currently set at 3 turns out and have tried 2 turns to 4 turns with no change.
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Steve
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