1970's LT10 36 Only runs at choke/full throttle

When I bought the mower it only ran up to full throttle and would stumble at full throtte. After tipping it on its side (oil came out the exhaust) to change the drive belt, now it only runs at WFO (wide frickin open) and dies as soon as I try to throttle down as if the ignition key was turned off...any ideas?

Thanks

At first it wouldn't start. I took out the spark plug and the carb bowl drain screw and let the gas run through it. I also turned the engine over without the spark plug in it. When I put the bowl screw/plug back in, I tightened it all the way. Now that I think about it, it looks more like a needle (with a spring on it) than a plug, Should I back the screw out, or is it supposed to be finger tight?

Ok, so I backed the screw out of the carb bowl and it will throttle down, now to find the sweet spot to run smooth throughout the throttle range. Is there a factory setting for the screw?