PA(J)S, how many turns?

4 replies to this topic
  • Littlefoot

Posted May 14, 2002 - 02:24 PM


o.k. I received ny jets and needle from Sudco.

For the Pilot Air Jet Screw, PA(J)S, how many turns = what paj and where did you get this information.

I called Sudco, first they told me:
1 1/2 = 100

then changed it to :
1 = 100
1/2 = 65
3/8 = 55

then told me me if I wanted specific jets, buy the jets.
Is there a table or matrix for this?



Posted May 14, 2002 - 02:59 PM


Here this is from Taffy. Where in Michigan are you?

--------------------------------------------------this is the article i put in a few days later
"as i hope this will be archived someday i thought i'd mention that with reflection i think that my final set up of 55PAJ/35PJ could be improved to 45PAJ/35PJ.
it's just one of those things that you reflect on and run through your mind. all my mods came from just "chewing on it".

my chart therefore reads;


this just about makes the gap 15 of PAJ to each PJ so this makes it a kind of easy to remember rule of thumb.

remember that the PAJ is there to drag the fuel out and you can only soak air with so much fuel before if you need more fuel; you need more air first. thus the ratios.

an element of the pilot circuit ratio works when you start the bike (40%), but just as you move off the bike wants to draw way more fuel/air than it could get past the needle so you must alter the PS to dictate the curve on this. so;

PS 1 turn out
starts with 'X' fuel/air and doesn't really get a lot more as you move off.graph flat.

PS 2 turns out
starts with X fuel/air but as you move off the mixture richens strongly. graph steeper.

so the PS helps you dictate what you get most of all from idle (hardly any help in or out)to 2-3,000 revs where it akes a big impact.

so what has the biggest contribution at tickover?
i'm guessing but i'd say that;
needle straight is 40%
PAJ/PJ is 40%
PS is 20%

the latter two though, are meant to be there from opening throttle to 2/3,000 revs and so we need to set the bike on idle with the needle diameter.

this as many of you know is the last suffix in your needle. so to richen the mixture at tickover we would for instance go from an EKP to an EKN which is thinner and passes more fuel.



i've modified my old article-even i can't make sense of the original. for those of you trying to visualise it; try this.

in your mind draw an upward sloping line 6" (nice'n shallow) this straight line is the optimum fuel line for your bike. now all you need is to start another line at the start and go straight and flat for 1 1/2". now a third line, this time from the start point and rising more steeply than the long line (1 1/2"). use a colour pencil to fill in an arc betwen the two shorter lines. it should look like a tilted up megaphone with a line coming out the middle.

now you've got it!

what it means is this;

the pilot screw can do little at idle. the mixture here is set by your needle. the PJ/PAJ are here to work from the moment you open the throttle to mid revs. you don't want to have it setting your idle, it's got more important work to do. SO YOU SET IDLE WITH THE NEEDLE STRAIGHT. the PC then does it's bit at low revs, the needle and MJ chime in later.

so what about the different PC ratios? what does 45PJ/75PAJ do compared to 35/45.

lets try 45/75 instead of the 35/45 we just pulled out...

well the tilted megaphone still exists. same angle, length, tilt the lot EXCEPT THAT IT'S NOW MOVED VERTICALLY 1/2" ON THE PAGE. so now the idle is rich (and you still can't alter it much with the PS).

two PS settings:
0-1 turn out
if you look at your graph the lower flat line still cuts across the ideal "fuel line" you drew so you're ok at say 2,000 revs. the problem is that it is chucking it in (rich)at idle and the PS makes no difference, also, that lower flat line went UNDER the "ideal fuel line" so at the extreme top of the PC's range when hitting the throttle in second at 15mph/3,000rpm we have a flat spot.

1.5-2 turns
as above we're rich at idle and not much we can do with the PS. now watch that fuel graph (yyeeeehhhhaaaaaaa)! it started above the IFL anyway and now it's in vertical orbit!!! this bike is rich. luckily the only thing that happens is that we get a slight "stumble". ever been there boys?

some of you will say; "well if the needle is 40% of idle (tickover) the PC is still the other 40% and the PS is 20% so we can use the PC to change idle surely?

ok, true but what a waste!!! the PC wants to be at around 35 to 38PJ and have a PAJ setting to suit (PAJ 45 for the 35PJ and PAJ 60 for the 38PJ) we then use the PS to get the angle of the curve right and to actually start the bike that leaves the needle straight!!!

another analogy for this is that we have a 50 gallon drum and we need to get it to the line at the top we might change all the PJ's in the world but the level in the barrel only goes up or down 1". not a lot is it? so the needle straight doesn't have to change drastically to "top it up".

i hope i've explained this well this time.


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Posted May 14, 2002 - 03:05 PM


SORRY wrong one.........Try this. Like Taffy says its also in the Patrick Burns Article -- good reading.


did you read the patrick burns write up? halfway through he has a full chart of the values of the PAS compared to the PAJ that it replaces. and larry you've got your figures wrong.

1/4 turn out from closed = 45PAJ equivelant.
3/8 = 55PAJ
1/2 = 65PAJ (note larry)
5/8 = 75PAJ
3/4 = 85PAJ
7/8 = 95PAJ
1 = 100PAJ
1 1/8 = 110PAJ
1 1/4 = 120PAJ
1 1/2 = 125PAJ

your problem larry is that your needle straight is far bigger than mine and this is worth, i dunno, maybe 20% of your tickover mix. on your thread i've asked you to describe your starting symptoms and this will help me give an opinion from 6,000 miles away whether you need a narrower needle straight. i.e. not an R, not a Q, not even a P but possibly a N or a M needle.

  • Littlefoot

Posted May 14, 2002 - 03:35 PM


Thank's WR.

I'm in Shelby Township, S.E. Michigan.


Posted May 14, 2002 - 04:37 PM



Hows the riding over there. I'm about six miles from Indiana and 40 Miles south of Chicago. I get out your way for the NASCAR race. Is the track near you. Looks like there would be some good riding out there.


Pete :)


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