I rode my "new", late-year `96 Scorpa EZ Fun 250 (black and yellow) at a
trial two weekends ago.  Very nice.  It did not feel strange or hard to
master.  Again my impression that I will like this bike was reaffirmed. 
I rode 3 classes down in Senior due to a bad case of the flu.  It made
the trial too easy, and I only took one point, but it was better than
damaging myself in the hot weather.  Still, I got to know the bike in
competition.

The motor ran great, but I felt as though it was not smooth enough right
off idle.  I suspected the timing may have been advanced too much for a
more ordinary (quasi Expert) rider like myself.  Fortunately, stalling
and lurching common to bikes with too light a flywheel was not a problem.
The Rotax has ample rotational inertia.

I earlier ordered a flywheel puller for the Scorpa from the Trials Shop,
so I whipped off the mag cover and flywheel to see what was in there. 
Ah, very nice and clean.  No corrosion at all.  Sprayed clear lacquer on
the parts to prevent corrosion.  Greased the tapered spindle and threads,
and then moved the stator plate.

The Scorpa's Rotax uses a conventional setup with flywheel on the outside
and lighting and other coils and ignition pickup inside, on a stator
plate.  This is a departure from the older Rotax motors with stator on
the magneto cover.  The stator plate is held in a counterbore in the
centercase, and affixed by 4 cap screws.  I noticed the position of the
screws relative to the slots was about 80% biased in the advanced
direction with full retarded being considered 0%.  I marked via scratch
the original position of stator plate relative to the center case and
rotated the stator clockwise or with the rotational direction to retard
the timing.  A big fat guess, I moved the scratch mark .12" on a stator
plate 3.55" in diameter.  Doing the trig, this came out to 3.87 degrees
the timing was moved in a retarded direction.  Since I do not know the
timing spec to begin with, I do not know the end result in terms of
degrees BTDC.  The screw position in the slot after this move became
about 40% in the advanced direction with full retarded as 0%.

The end result?  Idle dropped a very small amount.  A 1/16th turn on the
idle screw brought it back where it was before.  Starting is a bit
easier.  Power is noticeably smoother off bottom, with less tendency to
lag or surge at idle creeping in 1st.  Low end control is significantly
improved.  High gears and heavy throttle allow the motor to smoothly lug.
To test top end power, I went to a spot with a 6 foot wall requiring 3rd
and lots of throttle and rpm.  I still ended up pointed to the sky! 
While top end power is reduced some fraction, I did not notice it as
being enough to hold me back off the big stuff.

The bike worked pretty good before.  Now it works better.  I may
experiment with more retarded timing, but it's hard to justify, as the
bike is working so well as is.  With an impact wrench for the nut, and a
flywheel puller, the whole process takes no more than 15 minutes, so you
can do quite a bit of experimenting in a short amount of time.  I suppose
one could really retard the timing for mud events, perhaps as much as 5-6
degrees, and run stock or even more advanced timing for demos on concrete
or on super-sticky rocks at Nationals.

One thing that may complement this change is an increase in compression
as has been done on the `98 model.  That would increase low end
quickness.  While it would not be an advantage to the vast majority of
riders, the quickness would please the National rider.  I have done this
kind of thing on newer Fantics for years with good results.  Part of why
I did so on them was the relatively light flywheels Fantics have, even
after addition of maximum flywheel weight.  Retarding them helped with
traction and prevented stalls.  

I find it odd that this trick works so consistently to give power
characteristics more in line with the vast majority of riders.  Gas-Gas
figured that out and gave us smooth, hard-to-stall motors.  They were
rewarded with great sales of their bikes.  I can't confirm their timing
is more retarded than the rest, it sure seems like it.  Let out the
clutch at idle on a 270 and it will be damn near impossible to stall!

Why do factories tend to run many motors so advanced as to cause a less
advantageous power for the majority?  It is a mystery to me.  While I
know many who want the hard hitting, abrupt power characteristics, most
would prefer gutsy and smooth, with still strong enough top end.  If no
stop rules come to North America, this kind of power will be even more in
demand.  Since experimentation with timing is so easy and you can always
go back to what the factory set the bike to, I would encourage all the
able minded to dink with this if they suspect their motor to be on the
advanced side.

Chris (CJ) Johnson, Director of Engineering,
College Park Industries, Inc.     http://www.college-park.com
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
papazit "at" juno.com
Scorpa 250/Gas-Gas 160/Fantic 305/Three 650 Yamahas/BMW R75/6