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My 2004 raptor 660 has an inconsistant idle. By that I mean when you pull the clutch or come to a stop the quad will idle high for about 10 seconds, then idle down to what I would call an oppropriate idle, then after about 30 seconds it will die. Mods are as follows: 27.5 idle jets, 155&160 main jet, pro design intake, prodesign foam filter, Bill's pipe. I run 100% 93 octane gas. It runs great, does not eat plugs, no back fires. Any advice would be helpful.
 

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Have you checked for any cracks in the rubber intake boots between the air box and the carbs and between the carbs and the head? Also make sure the boots are sealed and properly clamped around the carb flanges.
 

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Sounds like you do not have your fuel/air mixture screw set right. The high rpm for a few seconds then dropping to idle is sometimes referred to as a hanging idle. Generally you are about 1/2 turn away from perfect fuel/air mixture on that circuit so try turning the fuel screws out 1/2 turn then ride the bike and see if that remedies the problem. Good luck.
 

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Too lean on the idle circuit mixture - most likely pilot jets are dirty.

Also possible that there's a vacuum leak, or the fuel screws have been set too lean. Try turning them out 1/4 turn (CCW) each.
 

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Too lean on the idle circuit mixture - most likely pilot jets are dirty.

Also possible that there's a vacuum leak, or the fuel screws have been set too lean. Try turning them out 1/4 turn (CCW) each.
If you are at 27.5s I suggest cleaning the pilot jets and fuel screw passages, 25s are a better choice, but for some reason, some bikes need 27.5s, which is bigger then the norm.................
 
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