Power jet Keihin carb

[michael harris]

not 100% positive in this scenario, but generally power jets are a boost for a specific rpm or throttle position. On motocross bikes they were used for 0 to like 50% as a boost in low end fuel to aid in torque. However on the same basic carbs but swapped over to methanol for microsprints the power jet was used as a 75% to 100% throttle situations as you couldnt shove enough fuel through the main jet. they added approx .080 to a main that was at .112 or so. lotta fuel for a 250cc 2 stroke..
44H

 

[Rhymingmechanic]

I'm not sure the terms are interchangeable, but the power VALVE on a Holley is kept closed by vacuum. It opens when vacuum drops, which would give more fuel at WOT. Engines with big sloppy cams often run rich with Holley's factory power valve because there's not enough vacuum at idle to keep the valve closed.

 

[mechtech]

That little valve is opened by a rod that is controlled by vacuum.
That makes it load sensitive - vacuum will keep it closed [normal running]. Low vacuum at high power demands will let more fuel flow through the circuits.
This is standard carburetor operating procedure.
A mfr may or may not have bleeds to the idle circuit, or not.
The valve serves to richen the mixture when needed.

 

[NJC]

mechtech, yes the rod which actuates the power jet was connected to a port which bypassed throttle plate down to manifold vacuum. That explanation makes sense.

I didn't have the carb off of the car so I didn't see where that passage (power jet) led to but it must have been under throttle plate.

 

[NJC]

Does anyone know the function of the "power jet" in the Keihin 2bbl carbs? It is item #30 in this link. I do know it interfaces with item #17, which is directly connected to idle circuit.

I think it is responsible for dumping more gas during WOT but it doesn't make sense with its interface to the idle circuit.

http://www.carburetorfactory.com/expvw31.html

This is on my '84 Accord 1.6L