Paj 1 & 2

[Rusty McNeil]

PAJ 1 & 2

How do these play into the fuel curve?

Do they have the same but overlapping function before the needle setting takes over?

Is one lower rpm adjustment than the other?

Or does one set a "Range" for the other?

All the literature I've found usually just talks about just one PAJ, and for us it's usually adjusting PAJ2 behind the slide, but what about PAJ 1?

Thanks guys

 

[MaxMidnight]

Sorry but I don't recall who the original author of the following was but his (or her) work is acknowleged.

Carb theory
Air enters PAJ1 and PAJ2 and is merged to extract fuel from the pilot fuel jet. The mixture screw controls the resulting mixture. The screw has an affect on carb operation up to 5000 rpm. PAJ2 is part of the coasting enrichment system and is closed at idle and begins to open starting at off-idle throttle positions.
PAJ2 is closed at idle and starts to open at small throttle openings. It's part of the coasting enrichening circuit so I believe it has the greatest affect at off-idle. PAJ2 combines small amounts of air with PAJ1. This combined air is used to mix with fuel from the pilot fuel jet. The pilot fuel jet has an affect up to about 5000 rpm.
I changed mine from 170 to 150 once, and off idle wasn't very good. There just wasn't a very good transition from the idle circuit to the needle (about 2500 rpm).

The needle has a tiny affect, even at idle. A very small amount of fuel can squeak by the needle at idle. If you put a more aggressive needle, you'll notice a change in idle. The jet needle controls how much fuel goes from the emulsion tube to the needle jet.

The idle, midrange and main circuits all bleed together so where one circuit starts and another begins isn't very cut and dry.

Some people do put a slightly smaller PAJ2 in to enrich up their off idle. IMHO, I think it's a waste of time. A slight turning out of the mixture screw will enrich the idle up just fine.

 

[one2dmax]

I know the PAJ 2 shows a change to the ENTIRE rpm range when doing dyno testing in the past. BUT, the biggest change was in the midrange. I have started gathering up the rest of the parts to complete my dyno and will be playing with it soon and will see what kind of hard facts I can get on these sorts of things.

 

[choctaw]

Keep us updated Sean,,,thanks for everything you do for the fraternity

 

[Rusty McNeil]

Thanks guys,

I'm trying to figure out how to lean everything out up to about 6000-6500 rpm.

I'm rich like crazy using the same jetting I had with the old motor except for when on the main which is lean.

Obviously I need a bigger main.

I'm thinking the rich down low makes sense since perhaps the PAJ's are not big enough to add the air needed for the amount of fuel the bigger displacement is pulling thru the carbs.

I'm going to try Sean's suggestion and swap the Mikunis 170 from paj2 to the main but I need something bigger than the Mikunis 170 to put in its place to lean out mid-low.
Going to play with the float and needle too.

I just didn't know if paj1 should get any attention in these efforts.