Does it have a safety switch on the clutch? I would disconnect the "Kill" wire from the engine and see what happens. The model number of the engine is always helpful especially since there is more than one 13.5 hp B&S engine and I for one have no idea what engine this may be.

Walt Conner

Is the engine "stalling" as if it just quits or "stalling" as if there is too much load on it?

IF the former, that's a "typical" symptom of a bad/misadjusted/disconnected seat switch.

Or something holding the blade possibly

Thanks for the suggestions everyone. I have found a simple solution. The battery while having enough charge to start the engine first time it has insufficient charge when load is applied. So as soon as the clutch is engaged, even in neutral, it stalls.

Since the engine runs on magneto, the battery state has nothing to do with it running once started except minute current required to keep carb solenoid activated, which alternator should more than handle so may want to look further.

Walt Conner

Just found this thread I posted and then lost track of. I have not had the problem come back - yet. The engine model by the way is 28TT707 Type 1121.
I agree that what I say "fixed" the problem seems unlikely so I may have to look at this again, soon as the winter weather improves.

That engine is only equipped with the Dual Circuit alternator.
It provides 3 Amps DC charging & 70 Watts AC lighting (if used).

The fact you have "enough" battery to crank the engine, means you have enough battery to run it for "hours" if the fuel solenoid is the only thing drawing current AND the engine wasn't charging.
Even if you had an electric PTO, that only draws 3-4 AMPS.
Starting requires over 100.

I'd look for a spindle or pulley binding.
You are engaging the PTO at higher engine speed aren't you?