"Nick Hull" wrote in message
...
I tried alt.electronics.repair and didn't gat any good ideas. I don't
expect you geniuses to solve my problem but maybe someone can point me
in the right direction. The 3-wheeler only cost $400 when I bought it
used many years ago!

Between the flywheel pickup coil (magneto) and the high voltage coil for
the spark plug there is a black box that controls the spark and its
advance. This box on My Kawasaki 3-wheeler is called the Igniter and
this simple tiny circuit board costs $400! It was designed before 1982
and contains one IC and a bunch of discrete components. There has got
to be a better (cheaper) way to do this.

The spark starts at 10 deg before Top Dead Center and advances to 40 deg
before TDC by 2000 rpm. Since electronics cannot advance time
apparently the pickup is at 40 deg BTDC and the pulse is delayed to 10
deg BTDC at low speeds. If the timing delay fails the spark reverts to
40 deg BTDC for all speeds, meaning the engine cannot run at low speeds
therefore cannot be started. Bad idea.

How could this black box be designed using components availiable today
to control the spark advance, preferably adjustable or programable so it
would work in a wide variety of ATVs etc? If possible It would be
preferable to have the failure mode at low speed advance. Certainly I
would hope for a price below $400. All suggestions welcome

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/
I had a Honda with intermittent electronic advance. It used a trigger coil
and a speed sensing coil. The speed sensing coil generated a voltage which
increased with speed, much like a generator. This voltage was fed to a
comparator, along with a decreasing ramp voltage derived from the trigger
signal. When the RPM was low the ramp voltage had to decay to a low value to
match the low speed sensing voltage, so the spark was delayed. When the RPM
was high the decreasing ramp voltage matched the higher speed sensing
voltage much sooner, thus advancing the spark.

Loss of the speed sensing voltage thus resulted in maximum retard of the
spark. It wouldn't run for beans then, but sometimes it would suddenly start
working and you needed to be holding on tight!

I think this basic idea is how many analog electronic advance systems work.
I imagine the speed sensing may be done by integrating the triggger pulses,
also.
Don Young