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Discussion Starter · #1 ·
Raptor 80 won’t idle. I’ve been through the carb twice and it’s spotless and all orifices are clear. Starts fine and revs up well but is slow to idle back down. When it does drop RPMs it dies unless you tickle the throttle. I’ve made gaskets where the intake manifold o rings are to ensure a seal. Currently running it in shop without air filter assembly to rule out problems there. I originally thought the low speed jet was clogged but I’m sure now it’s clear.
 

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Discussion Starter · #3 ·
True. However this issue is far more strange than what that would cause.
 

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Slow return to idle is lean.
Lean condition can be caused by an air leak(at carb, intake, head or base gasket or crank seals).
No airbox or air filter on can make enough difference to throw off the air/fuel ratio enough to cause poor idle and/or running.
The fuel screw should be between .5 and 1.5 turns counter clockwise.
Check the o-ring on the fuel screw.
Check the float height.
What did/does the sparkplug look like?
Is the petcock/fuel valve flowing correctly?
 

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Discussion Starter · #5 ·
Totally agree, definitely lean. I just received new carb. Also new filter element so we’ll see what that does. If not better then I start hunting other areas for leaks.
Thanks
 

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04 raptor 660. 686 big bore with open airbox/k&n. Big guns slip on exhaust
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Sixpack hit the nail with how's the sparkplug looking. That's gonna tell you the most about what's going on. In my experience slow return to idle has always been lean condition, either the carbs still clogged in orifices you can't see/ fuel flow not enough or you got a air leak somewhere.
 

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Discussion Starter · #7 ·
Ok gentlemen. New carburetor, gaskets and “O” rings at carb (both sides of spacer” and the manifold to head connection.

Fuel flow from tank to carb… excellent
Air box thoroughly cleaned.

New air filter element installed. Hose / tube from box to carb removed cleaned and inspected replaced.

🥴.
 

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Discussion Starter · #8 ·
Slow return to idle is lean.
Lean condition can be caused by an air leak(at carb, intake, head or base gasket or crank seals).
No airbox or air filter on can make enough difference to throw off the air/fuel ratio enough to cause poor idle and/or running.
The fuel screw should be between .5 and 1.5 turns counter clockwise.
Check the o-ring on the fuel screw.
Check the float height.
What did/does the sparkplug look like?
Is the petcock/fuel valve flowing correctly?
Not totally with ya on crank seals. 2 stroke engines sure. 4 stroke, I can’t see the connection there to the issue.
 
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