MF50 will not stay running

pull off the rubber hose between carb and air cleaner, start engine, as it dies spray teeny bit of starting fluid into carb

if it catches and runs a bit, you have gas starvation, if no change then you have ignition problem to hunt down

to check gas flow, pull carb drain plug, run gas into big coffee can, if you can fill the can without flow slowing down any, your entire gas supply line is OK

First thing you may check if you have the right gas cap on the tank it is supposed to have a vent to permit air to go in the tank when gas getting out.

For a test you can run it with gas cap loose and see if it is OK.

If it"s not the cap you may disconnect the gas line fitting at the carburator catch the gas with a can open the valve at the tank you supposed to have steady full tube gas flow.

Just my 2�

Joe Ferguson

BUT, you said both carbs did same thing so you likely have something else wrong, try the ether in case its an ignition problem