I have no experience with this engine but like any engine with these symptoms I'd try screwing the needle closed and make sure it will burn out a good prime.  Then open one turn. Repeat.  Then open another turn, etcetera until I find the needle's range for this setup.  Sounds like it's getting flooded.  Of course it could be a bad backplate seal,  the sleeve turned backwards, bad fuel head leak, on and on but try the simple first.

Dave

I had a lousy attempt at bench running my ASP 36a. Just got it back from Randy with a PA NVA and venture installed and all I managed to do was flood it. I got it running once for about 10 seconds and that was it , it fired several times but just wouldn't take off and run. Using a New Thunderbolt plug and had the needle out about 3-4 turns, gunna get some NEW fuel and am charging up my electric finger cause were expecting rain the next 3 days so It'ii have a chance to dry up. Am I missing some trick ??

HI
You need to turn the engine upside down, flip it many times quickly and get all the oil out of it, then when you try to start it again, be careful to not flood the engine, be careful and DO NOT turn the needle all the way shut very hard, if you do you will break the orifice hole out in the spray bar , on most any NVA. I would not even hook up the fuel line untill you prime the motor and then run the prime out, at that point hook up the fuel line and try to breakin the engines.
If the engine is quiting rich, close the needle more
Do not  ignore the tip about getting the excess oil out of the engine if it was really flooded,

Randy

Is this a round cylinder head .36 or the later "square" head .36? Dunno about the round head, but the "square" head engines want to run, starting without a battery on occasion. They like to sound kinda wet and squishy, at least side mounted. I have one inverted, but it's not broken-in yet, but I expect it to be much the same, eventually. 

I have NOT had this happen on a Randy Aero NV Assy., but on a ST CLONE NV Assy., I found that the "closed" position was not actually closed, only as far as the NV would screw in. On a Magnum .25, it would not fully peak, but it worked fine on a .46LA, because the bigger engine needed more fuel, naturally (pretty much).  For the .46, one turn open was therefore a viable starting point, FYI. Steve

here's a shot of my home built saw horse/test stand and the engine. I bought the break in stand from Don Ogden ?? in Florida ? memory's fading so I might have the name wrong but it's lasted years and is great !!

As an amusing needle valve aside, this past King Orange, Eric Viglione and I noticed that our PA-65s in our respective planes were running so identical that, on that weekend at least, we were running at the exact same needle valve position on both planes-the whole weekend!  Literally, one of us might go up first in the morning, and then conversation might go like this: "Hey Eric, how did that run feel?"  "pretty good, I might try backing out the needle to 3:30 from 4 oclock."  Then I would send my plane up with the needle at that position-perfect run, then eric (or vice versa) would set his to the same clock position and get the exact same run to the 100th sec lap time.  It worked the whole weekend and it was a hoot to see the needle valves in two different planes always at the same spot.