its a mag problem or its starving for fuel that is all it can be. especially if you can start it again within say 5 minutes. be sure to open the fuel tap all the way as they can shut off via vibration if not open fully.

Brand new mag even with a coil hooked up still won't stay running for more than 30 sec

Wonder if it would help to pull the air cleaner for the pony and hold a gas soaked rag over the intake. This could isolate a blockage in the air cleaner and perhaps identify a fuel issue.

its fuel.
empty and clean the fuel tank and replace the fuel line if its hose it can have a bad spot internally that cant be seen and is restricting flow.

get some small link chain like they use for hanging planters works well put it in the tank add some fuel and give it a real good shake and swirl around make sure every part of tank get a scrub tip out the fuel into a bucket so you can see the loosened crud and repeat until its no longer getting dirty or no more crud comes out remember to empty the bucket each time too.
i would perhaps fit a new fuel tap and a inline fuel filter one of the $10 generic one for cars with carbs works just fine.
also clean the vent hole in the fuel cap if it has one. ours didn't so we always had to loosen the cap so it would run with out forming a vacuum lock in the fuel system and it will vibrate closed might be a idea get a brass cap drill a vent hole and solder a pig tail loop of fine copper tube to it so it can breath and not let water in.

Hi Team,
if not already covered I would suggest to remove the sediment bowl screwed in multi disc edge screen and see what you get.
Over time a hard film buildup appears on the brass screens that even carby cleaner does not remove--in some instances in the past I have had to remove the discs and soak them in cleaner and use a small light wire brush by hand to remove the film.
The discs are shaped to keep them separated and so cannot be emery papered--from memory they are assembled in the stack so they alternate their timing so as to achieve the designed gaps that is the fineness of particle filtration.

If not already done, a place to check at is to remove the fuel line elbow at the fuel bowl entry as in the past I have blown air thru these elbows into the bowl without apparent problems and still had similar issues--there was floating crud that blocked the needle seat bore so remove the needle seat also and check for debris.
Cheers,
Eddie B.

well, hopefully, you can get it sorted out. hear a very good video to watch explaining how to start cat with a pony and how the clutch and pion latch setup works.

Could you put a timing light on one of the plug wires to see if your losing spark?

good idea to use a timing light.

Thank you it helped. Do you know where I can get a gasket for the exhaust manifold on a pony motor

well, I just got some from caterpillar part number 2F4752 10.56 each. most parts are still available from cat