You need to do some basic things to see what condition that engine is in.
Go to a big chain auto parts store and rent a compression tester. Usually the end cost is zero after you return it.
Maybe your friend can help.
Remove ALL the spark plugs.
Stick a screwdriver down the throat of the carb to hold the throttle plate and choke open.
Thread the tester into the #1 spark plug hole and crank if over with the starter until the gauge maxes out. Usually about 4 hits or so.
Write the number down and do the rest of the cylinders one by one.
Usually, the accepted variance is each cylinder should be within 10% of each other.
You may find a dead cylinder.
