No I would not pull the throttle barrel, you could actually damage the seal taking it in and out. If it was leaking at the pushrod tube...that was your problem.

As for missing carb or backplate bolts. YS engines are very highly tuned to the pressure inside the engine. The rear disc valve and the pistons stroke both up and down create the pressures that run the engine. If you have a leak any leak, missing bolt is just that.....will cause problems. Even if the carb or backplate appears tight it is probably leaking at some point.

See the bottom of the engine is not always in vaccum...when the piston is moving down it is in compression...this higher positive pressure can leak out if its not sealed properly...

If the prop is balanced and its still shaking things loose perhaps the crankshaft is bent even slightly can be a problem.

Troy Newman
Team YS