Sorry. I didn't notice you said impact gun. I use a half inch drive Dewalt drill motor. It doesn't have the hammer effect like an impact gun and it works fine.

I was only spin starting a little LS3 100. Doubt I could do it on a 250 but maybe if it had an automatic chainsaw style decomp in the spare plug hole it might work. Anyway I probably tighten my mag nut to twice recommended-- but I'd better not recommend that lol. Have done it on my 360 with plug out just testing spark. Think I was strobing the timing at kick start speed  come to think, & made easy work of it. I saw a random video once with someone starting a bike with a flywheel using a belt around the flywheel & around his scooter rear wheel minus the tyre. Or did I dream that haha.

If it has good compression and it's not firing with starter fluid you're not getting good spark at the right time, full stop. That's why two strokes are so nice to work on! Fueling is an issue (or not) that can be sorted after it fires/runs on starter fluid.

"I saw a random video once with someone starting a bike with a flywheel using a belt around the flywheel & around his scooter rear wheel minus the tyre."

You didn't dream it. Snowmobiles came with a webbing strap for wrapping the primary clutch to start them when the pull cord broke, have had to do it myself, on a 900cc twin. Thankfully the clutch is pretty big so it gives a good ratio for pulling.

Like Schu I've seen it done with a drill too!

Okay, Life gets in the way and it's been a while since I've updated this post. We finally got the bike going this morning and he's out riding it right now. 43 degrees and bright sun here in south central PA; too cold for my old bones, but not for a 19 year old!
The no fuel problem was due to the left side crank seal popping completely out stopping any sort of vacuum from being able to pull gas into the cylinder from the carb, we replaced the seal. We replaced the points and condenser and we now have spark again. One of our neighbors has a points buzz box, so stopped by his place to have him set the timing. The bike fired on the first kick!
I'm just hoping I don't get a call this afternoon that it stopped on him again.

Good news. I've forgotten what bike but guess 125 175 which seem more likely to push out old seals. When you said 43 degrees I thought too hot as were Celsius in NZ haha. Thanks for the update.

Yea, 175, 1971 CT1 in the US
Well, he said he went 3 1/2 miles close around home and it was running great, so he decided to go further. He was 6 miles from home, his cell phone rang, he pulled over, shut off the bike, answered his call and the bike wouldn't start again after he disconnected the call. I got a call to go get him. He's disappointed and doesn't want to spend anymore time on it today.
The story will continue...

Heat soak problem? Did he try to start it after it cooled down? My bike behaved like that, lost spark a couple minutes after shutdown. Leaving it sit for 20 or 30 minutes and all was good. New ignition coil fixed it.

Damn. Need to video record what it does & how it does it. Does it fade away like running dry on fuel. Or cut off instantly like ignition. Or run misfiring erratically also like ignition, like source coil issues--or secondary coil. I don't know but I'm full of guesses. 

Not a heat soak problem, wouldn't start once I got to him a good hour after it shut off, it was good and cold. Last time I was with him (last fall) when it did this it seemed like it had run out of fuel, probably when the left side crank seal popped out causing it to lose vacuum in the crankcase not allowing gas to be pulled in. There's no misfiring, I did look the source coils over closely when we were doing the points and condenser and they both appear to be in good shape. I'm going to try to have him bring the bike back to me today to try and diagnose what's going on...