Thanks to all who replied.

This seems to be the solution:

From my reading of the thread and a little thought I suspect the
interlock may only be designed to kill the engine *if both* the clutch
is engaged (and said clutch is flail drive clutch, not wheel drive
clutch) *and* reverse gear is engaged at the same time in which case a
simple series connection of the switched in parallel with the engine
kill switch should suffice.

Reply from Robin:


That would be a logical assumption and quite possibly the answer, but
the layout of the belts and clutch levers doesn't lend itself to this
being the logical layout:
There are two hand levers for the two clutches*1 (calling it a
clutch is glorifying it, it's just a belt tensioner arrangement), one
for the gearbox drive, and one for the flail drive. The clutch lever
on the left handlebar is set up to operate the left belt / clutch
arrangement which operates the gearbox drive, and the clutch lever on
the right handlebar is set up to operate the right belt / clutch
arrangement which operates the flail drive. A simple swapping of the
lever control cables will give the 'no reverse with flails engaged'
scenario detailed below - and as I said above, quite possible the
answer - but the controls / cables / belts layout doesn't lend itself
to this and would explain why the previous owner(s) had installed it
this way.

*1 Of the two clutch levers, only one has the cut out switch
facility.

Many thanks for the AFL bod who came up with this probable solution.
When back at work on Monday I will see if the cables will fit the
other way around.

cheers,

Robin



Cheers

Richard