Sam,
I agree ... do it at the PAJ2 as long as you don't have to go extreme
to get the results you are looking for .. ie: if you hit "reasonable
limits" which IMHO is a DJ150 on the bottom, (trying to richen) and a
DJ190 on the top, (trying to lean it out) .. then you should make a
pilot fuel jet change, (I am not advertising but take a look at the
jet "comparison" chart if you are doing this with Mikunis .. at ...
http://www.tcamp30.home.pipeline.com .. look under the "trash" section
for the chart.
You are trying to avoid making your mixture screws too rich, (which
are for idle .. a closed throttle pilot mixture job), or your needles
too rich, (which are for mid-range), to cover "open throttle" pilot
mixture shortcomings, (which can only be adjusted via the pilot fuel
and air jets).
Adding more air with the air jets or more fuel with the fuel jet is
like changing the temperature on a water faucet, (going from hot to
cold). Then up to a limit ... without regard to the "blend",
(temperature in this analogy) ... the actual size of jets you are
using to do this is like adjusting the "volume".
I think that it is also important to note that this "deprived" pilot
mixture situation is not the case for all setups .. I don't think you
will find this to be the case on bikes that run open Vboost .. in fact
it appears to be just the opposite. If you look back at Patrick
Ahearn's hybrid Stage 7 setup, (122+ RWHP/modified air box) ... he ran
a very conservative needle setting .. and still had to put a "bigger"
PAJ2 jet in than the Mikuni 170, (stock), and he was still using the
stock pilot fuel jets, (37.5), (so he was making his pilot mixture
leaner ... please correct me if this is wrong Patrick !!), ...
Then Charles .. not too long ago .. running a manual Vboost, (but
normally open), Stage 7 with individual filters ... He ended up with
very "open" needle settings but also had to put a "bigger" PAJ2 jet in
to lean out the pilot mixture to get the results he was looking for,
(made his pilot mixture leaner).
Annnnd not to write another novel here .. but important to clarify
this concept ... there was a recent post of dyno results for a great
Stage 7/pipe setup ... I forget who did it .. but they tried a dyno
run with the Vboost working normally on one run and open all the time
on another. The "normal" Vboost run had a bad dip rolling into
midrange, (just shy of 45K), and the "open all the time" Vboost
didn't. This supports the concept that an "open" Vboost subsidizes the
off idle pilot mixture ... and that additional enrichment was not
necessary. The "normal" Vboost run, (where it was closed at 45K),
wasn't getting this help and showed the dip because the pilot mixture
was just to darn lean.
Since Patrick is going to punch me out anyhow for using his research
... I think there is one other "secret to life" concept that he
clarified and is very important to remember to really do it right ...
Cruising at 3500 RPM and cruising at 6000 RPM is different ... When
you cruise at 3500 RPM you are running on the pilot circuit only ...
when you are cruising at 6000 RPM you are running on partially open
slides, (the needle), "plus" the pilot mixture. These must be adjusted
to work together or you will get bad performance on one end or the
other. Soooooo .. if you go too rich on the pilot you are just going
to be too rich cruising at 55 mph .. if you go too lean on the pilot
and make it up with the needle .. then you are going to cruise fine at
55 mph but be too fat when you are cruising at 90 mph and possibly
induce a bog when you are rapidly twisting that throttle wide open.
When you hear people say ... "I moved the needles out and the bike is
getting louder" ... it is getting louder .. and their pipes are
getting hotter .. because they are getting too rich and they are
burning the excess fuel in their exhaust pipes ... Like Patrick
described in his post for the "modified stage 7" ... you need to
listen for that nice "drone" at 6000 RPM .. and then you know you have
it right ... Then of course you need to listen at 55 mph/35-38K RPM ..
whatever ... and make sure you are not hesitating or surging there
either ... Then you know you have done it right.
A lot of people have tried to explain this on the list ... but the
"pilot cruising" and the "needle cruising" concept never really
completely sunk in until I listened to what he was doing with his
setup ... I am like everyone else .. and important stuff runs off me
like water on a good wax job .. but this is a very necessary concept
to grasp and essential to obtaining the very best driveablity and
performance.
Sorry for another novel Sam ...
campbell
----- Original Message -----
From: "C.O.M.E Racing" <[EMAIL PROTECTED]>
Subject: Re: TourMaster Carburetor Questions
> So why do people change pilot fuel jets, which is a relatively
difficult
> job when the PAJ can be changed so easily by just removing
diaphrams.
> snip <
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