Date: Wed, 07 Jun 2000 15:52:36
Subject: pa50 tuning
From: Ludo Van der Velden
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Hans Hartman's question
Is that Polini kit NR. 119.0028?
If so, what did you pay for this kit? I understand the pump is an extra?
Yep, i found it new in holland paid about 8000 belgian franks for it,
the pump is an extra, they don't make them anymore, I found mine second
hand in good shape. The pump is a very useful extra, make's the cooling

You seem to have the lot.
As an extra, you might reduce the crankshaft chamber's volume by adding
piece of metal (alloy) under in the sump (between the two crankshaft
counterweights). This results in a better (higher) under-pressure in
engine, this increases the performance a bit.

-I know of that trick, but I didn't do it with my pa50. Why? the
cranckshaft is the "weak"-spot, I already broke one on my other
"lightly" tuned pa50, I polished the whole inside of the
cranckhaft-chamber,and replaced the bearings with "C3" type bearings..
Be sure that the 21-mm carb gets enough air, if in doubt you could fit
Polini's air power box.

Well actually, that will be solved: I hope the carb wont take too much
space so I can fit a "double" air-filter straigt on the carb, otherwise,
I'm going too make another hole in the airbox at the bottom of the
"standard" big thing that holds your wheel... (how do you call it in
english?) So that I have 2 air intake's...

When you start adjusting the carburettor settings, begin with a too
main jet, and work your way down with smaller jets by trial and error.

Thanks for the tip!

I believe there was a special end-ratio kit for the PA50 too, you'd have
too check the Polini-site for that.

I know, but they don't make it anymore, but that end ratio is for higher
speed, and that's one thing I have plenty...a high topspeed is not my
goal, I want real fast acceleration!

What alterations did you do to your variomatic system? Did you replace
centrifugal clutch spring's (3) with heavier springs (+40 percent)?
weight rollers did you use?

I have the 6 roller version of the variomatic, I recut the vario so that
the weights can move a longer way...I wil install heavier springs, but
you may only do that after about 500 km's or so... I'm experimenting
with different weight rollers, I want maximum acceleration...

I discovered an edge on my primary pulley, which restricted the belt
further down. After we've machined that one off, the end speed was a bit
faster (from 45 to 55 KM)
We did not remove the edge entirely, because a lot of pulley axles were
broken in the old days.
I do know Belgium used other pulleys, but I am not sure the edge is on
model too.

Well a problem that exists is that the pulley get's the "Edge" after
extencive use... I just bought a new one, new one's don't have an
edge... over here.

Does your model have the six-roller version or the three-roller clutch?
6 roller, but legend has it that the 3 roller should be better for high

The Polini kit and the expansion type exhaust you use, will shift the
maximum torque from 5000 Rpm to 8000 Rpm, you must adjust the clutches

I know...a friend of mine will do that.

I am going to fit my PA50 with an electronic ignition unit for the Honda
PX, as far as I can see right now, everything fits.
When you use an electronic ignition, you can discard the flywheel, and
a battery ignition instead. This will cause your PA to howl to it's 8000
(or more) rev's quicker, thus improving acceleration.
Of course, you don't want to do that when you're going to use it on
bases, because the moped stops when the battery is empty of course.
In moped races in the Netherlands this modification is common practice,
all modern scooters and mopeds have electronic ignition.

Well, that's one thing that i might concider changing on mine...

This however is not the reason I want use the electronic ignition. I
want to get rid of those contact-breakers, and like to experiment a bit.

How do you measure your speed? Over here everybody uses these bicycle
computers, which are really accurate when the set-up is done right.

I use a bicycle computer... I also have a rev-counter...It still needs
to be driven in... and a rev counter helps if you don't want too screw
up the whole thing...
Hope this helps,
Thxs for your comment!

PS:not that it's a problem but my name is not Ludo... i'm using my
fathers email addres...

Hans Hartman

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