When setting the ignition timing, the first important step is to check that
the pointer on the crankcase lines up with the T ( Top dead centre ) on the
rotor plate, when the piston on number 1 cylinder is at top dead centre.
The Ignition systems on the Australian models
1978 'E' 2H9
1979 'F' 2H9
1980 'G' 3X1
1981 'H' 3X1
All operated the same.
They included the backing plate with adjustment slots, a mechanical advance,
and a vacuum advance unit.
The standard timing was 5deg at idle for all these Australian models. The
5deg idle advance made the engine idle smoother.
The mechanical advance unit number was 2H7-11.
Full mechanical advance was 36deg at around 4.600rpm. This was measured with
the vaccuum advance hose clamped shut.
Vaccuum advance is listed at 16deg at 150mmHg, but this is very difficult to
measure with the mechanical advance fitted.
Normally you should just check to see the that the diaphragm is operating
the ignition plate when you rev the bike up.
The RH model is completely different to these other 4 models.
1981 'RH' 5N5
On these bikes there is no mechanical advance unit. This is done inside the
ignition box. Consequently the ignition backing plate has no adjustment
slots, just fixed bolt holes.
The vacuum advance diaphragm is still fitted, and operates the same as the
other models.
On the American models there were differences.
The original 'E' model was prefixed as 2H7, and many parts from these models
fit the Australian bikes.
The mechanical advance unit for the US was 2H7-10.
These units were set at 10deg static advance and 36deg on full advance. The
10deg advance tended to hunt a bit more at idle, but had less of a doughy
spot when you cracked the throttle to take off.
Many American models went to the fixed ignition systems similar to the
'XS1100RH' model quite early to comply with more stringent emission laws
over there.
Regards,
Mal.
