Lock tight or no?
 

I traded some work for a replacement 14 HP for the 149. It is complete with correct PTO. The starter/gen pulley was loose so I pulled the PTO and installed a new bearing, checked pulley, it looked ok but key had a little wear from running loose. I turned the key and all felt tight so installed pulley and tightened it up and put PTO on. Installed it on tractor and started up. It has a walbro so after some adjusting it ran good, pulled back inside and checked. The pulley was loose so I tightened it back up. Last night I finished mowing with the 109 which has a lot of piston slap and getting weak, so I focused on getting the 149 finished so I won't blow up the 109, got a fuel tank on it and ran it again, within one minute the pulley was loose again. Am I not getting it tight enough, should I tighten one set screw first or does it matter, should I locktight the set screws, or is it the key wear that is causing this. The motor sounds good so I am going to get it going this weekend before the other blows up, just have to get this fixed and should be ready. I would have pics but some slug broke my window and stole my GPS and camera.

Try replacing the key, they're like 50 cents and should be replaced anyway.

Figured I should, what size are they? I don't have it apart and will be out in a few minutes.