Howdy yall, 
     I have a 1970 at1-B That will not start. I have gotten it to start by putting a little fuel in the cylinder through the spark plug hole, so I believe it has a spark that is on time, but it will not start from the carburetor. The oil pump is not hooked up as it is a barn find, but it should still start without that. I know not great, but I have parts on the way and once I get it running a full engine rebuild is next. I have replaced all the jets with mikuni jets recommended by the manual and cleaned the carb as well. The air intake gasket is most likely oem, so a vacuum leak is possible, but it looks to be in good shape. The idle adjustment (Throttle stop) screw is 2 turns out, and the air-fuel screw is 1.5 turns out. The throttle cable is adjusted with a touch of slack before engaging. Float moves freely and is properly adjusted. Carb bowl leaks fuel slightly, but I am in the process of correcting that. Running out of ideas, any help would be appreciated! See carb jets in attached file 
 

By starting did it just fart or run briefly. Reason i ask is i'm thinking "barn find" poked a crank seal out. I guess you don't realy want to 'go there' but it should at least try to start spraying something in the carb mouth with it wide open so it gets to the cylinder. But if it 'has' pushed out the right side seal it won't want to suck fuel to transfer it up top. Which is why 'i think' you might be getting a sign of life down the plug hole. Hope i'm wrong. Could be lefty seal but right seems more common to escape.
I shouldn't show you my bad tricks but if i can find it easily i had my 100 running on what we call CRC-5-56 pentrating oil straight in the cylinder. I might add that mine hadn't pushed a seal out & was just carburettor was the worst i've seen, so was just impatient to hear it run.

Ok found it. Hang my head in shame haha, was a while ago. Little bike went like a rocket too, wheelies up the drive etc.