Anyone experienced long delay from the time throttle is reduced to idle to the time the engine actually slows down to it's lowest idle speed. Approx. 10-15 seconds is required for it to come down to about 1700 rpm. Any ideas as to why the long time delay is required for the engine to finally slow down ? Everything else is normal. Engine not rich or lean. Throttle response confirms this. Once engine finally slows down it will hold the idle indefinitely no problem. Any help from you Mokit guru's ?

Idle is too rich

Check the O-Ring on the low speed disk. You may have a small air leak or tear. I think Hobbypeople.net carries new ones (Mark Engine). Also what plug and fuel are you currently running, along with prop size/brand and are you using a CLine Reg.

1700rpm is still very very high for an Idle. How is the transition from low to mid & mid to high? It wouldn't hurt to pull the carb off and apart while flushing and cleaning each area well.

Here you go
http://www.hobbypeople.net/gallery/214576.asp

also this
214539 10.180/21 Mark Engines O-Ring - Mark 180/210/360 Carburetor

All O-rings have been replaced with new ones, so that isn't the issue. When adj. the low speed one more click leaner rapid throttle advance will make engine cough and die.

You have an air leak somewhere

Air leak could be the problem. Anyone know a good to way to find the source of the leak ?

Rounding up the usual suspects . . . . It's under the carb or the carb retainer

I would checl the orings. It is easy to cut these when installing.

Under the carb would be the O-ring. The carb retainer could be the culprit maybe. How about if I put some silicone sealer over this area ?

sounds like a winner