Pony #1

#1 is LH side as viewed from the seat.

Thanks OM. I guess it should be obvious but when using a engine for a power unit or a genset, the term "left" is kind of ambiguous.

When viewing equipment, pumps, motors, gear boxes, etc rotation is always viewed from the drive end. (Industry Standard)

Hi Tom,
A faulty spark plug can cause the spark to cross over inside the mag cap or across the rotor button if it/they are covered in carbon dust and/or cracked. The cracks/burn lines, fill with carbonised cap/rotor material that becomes conductive to the spark, if you find this, for the cap carefully gouge out the carbonised material and spray it with electrical lacquer insulating spray.
About all you can do with the rotor is face it up on sand paper to remove the tracking lines--finish off with fine sand paper to leave a smooth surface for the carbon brushes to rub on.

Another thing is to check you have metal core wires--carbon core resistance wires and/or resistance spark plugs and magnetos do not mix well as the mags cannot fire thru the resistance.
As above check your cap and rotor for carbon tracking and/or cracks that can cause the spark to take the easiest path to the other cylinder.
Timing is affected by incorrect points gap.
Eisemann mags for D2/D4 ponies run 0.020" Other brand mags run around 0.014-0.018". Mike Meyer and I found that running an Eisemann on a D2/D4 pony at 0.014" will require the mag to be set one tooth out for correct points opening versus the flywheel timing mark.

Carbs with the later horizontal main jet adjusting screw can have the 90# (scan 1 below) lever under the little cover that the adjuster screw is in can be bent to more than 90#(scan 2 below). When this happens you cannot get the mixture rich enough for the pony to run at less than about half choke.
The lever is flimsy and easily bent if you use more than your fingers to screw the screw IN to reach the jet adjust start point for initial adjustment--then screw out 1 turn-- and then adjust for best high speed power running-the adjuster screw works in reverse due to the 90# lever, so turn IN for Richer--OUT for Leaner.
Hope this helps.
Cheers,
Eddie B.

Wasted spark ignition systems have become so common, it is hard to purge that from my troubleshooting process, but even though the horizontal opposed pony is an even fire design, it should NOT run if timed to the wrong cylinder as #1.

However fixing that mistake is as easy as swapping the wires in the mag cap.

Got the pony cooking on the front burner. Man, a little time in some carb cleaner and some new gaskets does wonders for the carb.

The main jet at the bottom of the float bowl appeared to be at least partially stopped up. It seems like poor design to put any +- .030" orifice which has a good chance of being stopped up with small debris that would collect in the bottom of the float bowl.

Thanks,
Tom

Hi Tom,
great to hear you got that pesky carby sorted. It does not take much to cause a problem with them.
As you suggest they are good with a new clean system, BUT, after many years of getting topped up with dirty funnels and cans -- not to mention condensation -- it all goes south way down the track as rust and silt take their toll.

If your carb has the horizontal Main jet adjuster screw I found on one of Mike's carbs that the little cover did not cover a miss-drilled hole in the top cover. Over the years this allowed dirt and water into the bowl. The bowl was badly corroded and passages were blocked with corrosion material--really took some cleaning.
I filled the hole with some goo and it should be good for the future.

I posted a Thread "Pony Engine Quirks" -or something like that, about some idiosyncrasies of pony engines and their accessories some time back.

As the Search function does not seem to work here down under, up top there you may be able to find the thread and add to it with your experiences.
Cheers,
Eddie B.