Surely someone out there has a solution to my problem....Please help

2003 LTA50 Suzuki Quadmaster that ran perfectly until it decided to never run again.
Mods: none, completely stock restrictors and carb jets.

It's getting good fire at the plug (so yes, I've checked the key, tether cord, magneto, and "on" button)
Compression is 90lbs. That's with a guage that I had to hold into the plug hole with one hand and pull the start rope with the other. (it doesn't screw into the head)

I pull the spark plug out and dangle it near the plug hole, put the fuel petcock on "prime", pull the rope, and it ignites the fuel in the cylinder.
BUT, when I screw the plug back into the head, and do everything else just as before, the moter won't hit a lick. Yes it is the right plug and I did pull the head off to make sure it wasn't hitting the piston. I've even tried two other new plugs..same results.

It appears to be a lack of air in the cylinder.?.?.? And yes I've checked the air filter. I even removed the filter but it didn't help.

I've also posted this in the Kids Quads section if you wanna read the ideas posted there.
Here's the link Suzuki LTA50 Problems..please help

 

from what i read you need a rebuild had a 90 eton do the same thing pulled it apart check piston clearance and ring end gap both out of spec put new parts in fired up ran like a champ

 

Thanks for replying mudgeek...
I'm thinking my compression is low, but still high enough to atleast cause the motor to hit. It does nothing. I can pull the rope easy, pull it hard, 5 times, or 500 times....nothing makes it sound any different. I can put the fuel on "prime" or "on" and it doesn't change anything. I can pour fuel directly into the spark plug hole, replace the plug, pull the rope and still no change. Hotter plug, colder plug...still no change. Choke on, choke off....air filter off, air filter intact....you guessed it, no change.

Does anyone know how much spark I should be getting? And how could I test mine?

Thanks.