I have a cat at 12 with a d 2 Pony motor on a 318 motor it fires on one cylinder can't get it to fire on the other cylinder not sure what is wrong with the pony motor .Some help would be appreciative have compression and spark on top dead center as far as I can tell.  backfire through  carburetor the intake valves are not stuck have compression in both cylinders on the pony motor. HELP

Hi Pyobluebonus,
first thing I would suggest trying is to swap the plug leads over at the magneto cap and see if that rectifies your issue.
It often happens that the wrong lead is connected to the wrong cylinder.
Your pony will be similar to a D2--being a horizontal opposed twin cylinder engine--but is simply larger and so produces more horsepower to spin the larger engine.
Let us know how you get on.
Cheers,
Eddie B.

I changed the wires no luck. Fires on 1 cylinder

One of the several things that can cause that, is a dirty or cracked/damaged cap, if there is a path for the spark to travel to the wrong place, sometimes along a crack filled with carbon, it could cause both the non firing and the backfire.

Pyobb, could you give us a little history about when the problem started. Had the pony been operating normally and this happened all at once? Is it a case where you never had the pony working properly or at all? Is this pony "new" to you? That kind of history would be most helpful otherwise it is like throwing darts at a board to see what sticks. Background information is very helpful.

It ran about 12 years ago and then the coil and points failed pulled the Magneto off had it sent in to get rebuilt marked everything on the Magneto and the impulse coupler for proper timing on how to reassemble it the same way it was removed. Reinstall it and i have spark on compression stroke on both but will not fire.

I recently had this problem and found the air cleaner was plugged up.

I had the air intake pipe off

try switching spark plugs that will help rule out wires and plug or plug gap. with it fire if you add a little gas in one cylinder hole I would like to know a little more about how you got a D2 pony onto a D318 ? as I having trouble finding parts for my 318 3.125" bore pony but do have D2 D4 2.750" bore pony's laying around.

I was told it was a d2 but the bore is larger than 2.75 so i guess it is not a d2. I did put new plugs in. I have to figure out if i do have it timed correct. Need a manual or directions