Date: Fri, 24 Sep 1999 20:40:19 -0400
Subject: Scorpa Analog Controller
From: Chris L Johnson 

Finally, something new to pass on.  Not many Scorpa riders out there, but
maybe this will be at least entertaining to you non Scorpazoidal units.

Life has many mysteries, and here is another one.

Scorpas from `95 to `99 have an electronic hickey do called an analog
controller that lives between the stator ignition output and the coil. 
On the `95 it is a rather bothersome affair up on the forks.  The wires
will fatigue and ptzfft!  No ingintion.  On the `96 on, it lives under
the "seat", being fastened to the rubber flap that serves to pad the rear
of the fuel tank.

Just why did Scorpa add this component?  It increases cost, clutter, and
complexity, and actually makes the bike run poorer.  It reminds me of the
"power" valve on my `96 Fantic Section.  The governor whined, the valve
actuation cable would rust and stick, and it did nothing I could feel for
the bike.  Little to no difference if wire wide open or wide shut. Sniff
sniff....do I smell marketing BS?

I think the analog controller intent was to make the Rotax more trials
friendly by constraining the motor.  Nice idea, poor execution.  Perhaps
it is more appropriate to constrain the 280 motor?

After the analog controller was amputated from the bike, it still had the
wonderfully smooth low-end power I have come to love on this bike.  What
changed was the mid-to-top hit.  It was stronger, but not objectionably
so.  Certainly nowhere near the `99 Bultaco hot rod I rode with Keihin
carb, with it's mega mid-range burst.  The Scorpa just plain ran better. 
Still a pussy cat down low, but better, more controllable response mid to
top.

DETAILS DETAILS

Coming from the stator output are three wires of interest to this
discussion: a red, a white, and a brown.  There is also the typical
yellow 12V AC wire to power lights, and perhaps even a green wire for the
fan (I did not trace this one down).  

The analog controller sits on the red, white, and brown wire circuits  My
guess is it somehow counts input pulses of plug firing control, then
changes output to the coil to affect ignition timing.  But what do I know
about electrons?  I can't see `em.  Maybe some intelligent chappie can
enlighten us on the details of this analog controller?  I'll remain Dr.
Empirical.  Works pretty well most places, except astro and sub-atomic
physics.

Anyway, the pinout for the coil, looking at the socket where the
connector plugs in, is red at upper right, white at upper left, black at
lower right, and brown at lower left.  The black wire is for the kill
button.  When the analog controller is removed, the black, red, white,
and brown wire simply plug into the coil.  I don't know what the red,
white, and brown wires specifically do.

HOW TO CHUCK IT

After being given some simplistic info on doing this mod, "yeah, just run
the red, white, and brown wires straight into the coil....", I pulled the
tank off to observe the same intimidating gaggle of wires I shied away
from during set-up.  My bike came with the wiring harbess for the lights
still tucked in there.

The Scorpa is so compact under the tank, there's barely enough room for
the wires and throttle cable.  To help figure out what I was looking at,
I first removed the lighting harness (what the yellow wire feeds) and
lighting voltage regulator that sits directly behind the fan.  Our
wonderful Euro buddies attach this with a nylock nut almost impossible to
get to.  You don't have to take this off.  The harness just unplugs from
it (two-wire connector). The fan voltage regulator is not the squarish
lighting unit I removed form my bike, though the wires run close together
and one might think it's for th fan.  The fan regulator is up and
forward, and attached to one of the fan struts.  This is supplied by a
separate circuit. 

To be able to remove the harness, you will have to take out the screw for
the front of the coil to be able to get the lighting ground disconnected.
 Ah, much better.  Less clutter.

What was left was still a gaggle further back at the head stay.  A mess
of wires and throttle cable passed through the two plates of the head
stay.  It's tight in there.  

The analog input wires run through the head stay, and the output harness
to the coil runs right past, in the same constricted place.  The
connectors at the stator wire ends are sealed with heat shrink tape, I
imagine, to save space.  The heat shrink I sliced and peeled off.  This
revealed a curiosity: the white and brown wires were jumpered together
between the stator wires and the analog control.  By running the wires
directly into the coil, they would not be jumpered together.  Wonder why
they did that?

Another inconvenience is the analog connector that plugs into the coil
will not pass though the frame so the analog controller and harness can't
be removed without disassembling the connector.  I had to pop the metal
connectors out of the plastic housing, then remove the sealing boot to be
able to pull the wires out.

Now the analog fellow is gone, and your left with plugging things into
the coil.  I'd suggest using the white plastic connector housing and
sealing boot from the analog controller harness.  My kill button wire was
too short to use the connector housing, so I put heat shrink tape on the
four connectors and simply plugged them in for now.  You definitely don't
want to short these together, and it is better to seal them off from
water.  Later, when I replace the kill button with a Yamaha unit, I'll
slickify it with the housing and boot.

You also have to remove the two screws holding the rubber strap the
analog controller used to be attached to.  It serves as the rear gas tank
pad.  You need to tape or zip tie it so it won't part ways with the frame
some inappropriate time and cause you points in a section `cause you
can't figure out where the buzzing's coming from.

That's it.  Less wires, less complexity, and the bike works better.

The description above was from a `96.  The `95, particularly, may be
wired differently.  Nevertheless, once you understand the above, you'll
be able to figure it out.

Chris Johnson
Scorpa 250 EZ Fun/Gas-Gas 160/Fantic 305/Yamaha Virago 1,100/XV920RH Euro
and now vintage `74 TY 250
chris "at" college-park.com as Director of Engineering at College Park
see www.college-park.com and papazit "at" juno.com (personal address)