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There are electrical jumpers on the circuit board. Jumpers "A" (closest to green wire. some models have two.) control the whole ignition timing curve (to be more advanced or retarded/delayed) which has the most affect at low RPM. Jumpers "B1" and "B2" control the amount of retard curve to the timing without changing the low rpm timing, which has the most affect at high RPM. Below you can see the graph for the
A jumpers and the resultant timing curves resulting from what jumpers
are in place. (X is "no jumpers")
 Here you can see the graph for the
B jumpers and the resultant timing curves.
 DETERMINING BEST JUMPER
SETTINGS: You need to test the settings for
your bike to see what works best for your engine.
Jetting, porting, compression, and
exhaust pipe all affect the needed timing. Test jumpers A at idle
and going up hills (at low to mid rpm) and test the B jumpers for top
speed on a level
road.
Which ever jumper setting allows the best power is the setting you
should use. A needs to be tested first since it also affects top speed.
As an example here are my test results with my 55cc reving to 9200RPM
after selecting to have no A jumper installed: (FYI: B2 adds twice the amount of
capcitance that B1 does.) HOW TO UTILIZE THE JUMPERS:
Just remove the boxes 4 screws with a small Phillips screwdriver. If
your screwdriver doesn't fit in the screw head properly then it will
slip when turned. Don't go any farther if this happens. Go directly
to a store and buy a fine-tipped screwdriver that will work
properly. Otherwise you will ruin the screw heads. Once the box lid is
removed you can see the black jumper locations. The jumpers (which are
loose in the packaging) can be easily placed onto the receptors by hand
or with a needle nosed plier. Keep the
removed jumpers in something that is sealed such as a zip-lock
sandwich
bag so you won't lose them. Once you settle on jumper settings you can
remove the protective strip from the double backed tape on the box and
adhere the box to your bike frame.
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