Hi Team,
if the magneto is a bit weak try closing the spark plug points gap down to 0.016"-0.018"
I have also had success with rubbing some pencil lead across/onto the plug electrodes--this gives a flash of spark for one or two sparks that can fire a reluctant engine easier.

Also be aware that gas/petrol diluted engine oil can make starting difficult, usually occurs if the pony fuel tank tap was left on at some time and fuel floods down into the engine whilst the carby float is being bumped around during tractor operation or over zealous use of the choke when engine is reluctant to start--use cylinder drian cocks to clear the cylinders of excess fuel.
Change of pony engine oil usually gets results in a couple of pulls if the oil was diluted.

There is only about 1 Quart of oil in a small pony so it is prudent to change it more often that Cat recommended back in the day--125 to 250 SMU depending on dust and moisture conditions.
Cheers,
Eddie B.

I ran a D7 6T dozer for 12 years and had very little trouble starting it with the crank on top of the hood and never had any broken arms ever. Now the D6 was a little bit different as it could be a little stubborn at times. The biggest problem with it was in the winter time when it was colder and you went to engine the pony to turn over the diesel, it didn't have the High - Low transmission like the D7 did. That really made a difference. catskinner