Jake,
I don't know what tools you have available, but as suggested you should check the points as Rhys says.

I have had problems like yours and it turned out to be something kinda stupid (on my part). I'll elaborate if you want. I've been there and I may know what's wrong.

It sounds like you have a no-fuel problem. Stalls and endless cranking.

I recommend that you.
1) open the reservoir caps on the carbs, be sure gasoline is in there. If it is empty, check any fuel filter you have in the fuel line and replace it. EVEN if it looks clean!!!! I got hosed by a clean-looking paper filter that was clogged all to heck.

2) If there's still no fuel. remove the hose from the carb side off the fuel line and put it into a clean tall glass soda bottle. Set the bottle somewhere secure under the hood and crank the engine for a bit. Check the bottle, you should see fuel in it. If not, suspect your fuel pump. Don't give up on it too soon, it can take a bit to get the fuel sucked up through the system. SO crank until you are satisfied that it works or doesn't work.

As they say: this is gasoline, not orange juice - BE CAREFUL!!

If you have fuel, be sure you have fire.
If you have a timing light, hook it up to the #1 sparkplug and be sure you have a pulse. If this is an inductive clip-on timing light, be sure you are getting a pulse from the coil to the dizzy.

It is possible that you might have fuel-fouled the spark plugs. Remove and clean them with Gum-out and you'll know more. You can follow Ron Kwas' timing setup instructions to determine if you are getting a real spark in the chamber.
I'll elaborate on that if you wish.

If you have liquid fuel and spark, check your timing and if that checks out - suspect the fuel.

Then and only then consider if you have water or dirt in your fuel