Pop pop on exhaust side
The idle port is restricted by the idle mix screw. Those let us do some fine adjustment to the idle mix, but they are only part of the story.
The transfer slots also feed fuel at idle. The portion above the throttle blade also bleeds air into the mix, speeding the fuel along.
The more the primary throttles are open at idle, the less restriction to fuel going coming out the transfer slots below the blades.
You can check amount of slot exposure below the blades at idle with feeler gage or drill bits.
While you're at it, write down how many 1/4 turns in of the idle speed screw from just touching gets .020, 030, and .040. Then you'll always know how far open the throttles are.
Idle circuit is a misnomer. Low throttle circuit is a better way to describe it.
As the engne comes off idle, the portion of the slot under the blades becomes more open and the air bleed less. Fuel continues to flow with increasing throttle until the main circuits fully take over.
So idle, decel, off-idle, and cruising on flat up to 50 to 60 mph.
The idle port is restricted by the idle mix screw. Those let us do some fine adjustment to the idle mix, but they are only part of the story.
The transfer slots also feed fuel at idle. The portion above the throttle blade also bleeds air into the mix, speeding the fuel along.
The more the primary throttles are open at idle, the less restriction to fuel going coming out the transfer slots below the blades.
You can check amount of slot exposure below the blades at idle with feeler gage or drill bits.
While you're at it, write down how many 1/4 turns in of the idle speed screw from just touching gets .020, 030, and .040. Then you'll always know how far open the throttles are.
Idle circuit is a misnomer. Low throttle circuit is a better way to describe it.
As the engne comes off idle, the portion of the slot under the blades becomes more open and the air bleed less. Fuel continues to flow with increasing throttle until the main circuits fully take over.
So idle, decel, off-idle, and cruising on flat up to 50 to 60 mph.
