G'day Norm,

A car starter would be like drill starting as generally they are between 0.8 and one and a quarter HP but would still require a fair
amount of work to get it hooked up.

Yes I was thinking before the same thing with a remote Victa decompressor if you have enough room to drill the head ,but without
taking the head off it will make it more difficult to see exactly where to put the fitting and to stop swarf going into the engine

If drilling the head ,if it was me I'd set up the decompressor in the spark plug hole first just to make sure the motor turns
over with the decompressor ,that way you can work out what size fitting and hole works best.

Another way would be to drill the spark plug thread out bigger then tap a thread and install an adaptor with the fitting connected
to the adaptor then the spark plug would bolt in the centre of the adaptor.

Yes it's starting to sound like a lot of time may just be easier to buy a new cam and sell the mower straight after.

Cheers
Max.