LMAO!!! I recognize that cry at the end!!!!
It will be like that for a bit. It will run for a bit then quit. You'll find something needs tweaking, then it will run a bit longer; rinse, lather, repeat.
It does sound like it's firing a bit out of balance. I didn't slow the video down to determine which side is weaker but you can do that. The video capabilities now are great for slowing down time and seeing what's happening. Check your compression balance and look for leaks. Especially on the rear packing.
Damn, get it all back together, needed a new O-ring, I used the wrong type. Regardless, the damn thing sheared the tapered pin and silver solder on the flywheel side. Maybe I need to make one piece crank?
Oh no... That sux!
I've always done 1 piece cranks. I guess there are pluses and minuses to each.
You may want to look into timing? The power stroke may be a bit too early and resulting in a more violent stroke. Since you aren't really powering anything, there's no need to fire too much earlier than TDC.
That is where I guess the timing to be, TDC Using the timing light on the ign and visual on piston location/crank. I am pretty much lousy on working steel with any kind of decent finish. Did you start with 5/8" for your one piece?
That was one of the parts I documented pretty well. http://www.teqknow.com/Shop/Mery2.html about 1/2 way down. Just take your time. I've seen your work you got this one. It LOOKS much harder than it actually is.