why does my tractor rev slowly and drop rpms when i mow?

Question

this is a B&S 17.5hp, OHV, single cylinder engine, labeled as a Craftsman I/C engine.

this engine is 2 years old, but barely used. i just started using it today and it sounds like this. cuts the grass fine, but my old 17hp (almost exactly the same as this one) worked much better then this. it never bogged down unless i was cutting through really thick grass or pulling a heavy load, and when i engage the blades, it got up to speed in less than 2 seconds and ran at a higher rpm.
this engine also takes a while to get up to redline. my old engine was quick revving like a car.
could this be from an improper fuel/air ratio?

i also installed it myself, what could have gone wrong? everything fit the same as my old engine.

i should also add that when i am mowing, and i drive up an incline or shift into 5th gear, the rpms drop further, but sill maintaining enough speed to cut the grass smoothly.

i forgot to add the link:

http://www.youtube.com/watch?v=HkIN90cPPOU

Answer 1

Hi Andy,
Check the rods going to the carb. One is for the choke and the other is for the throttle. I bet the one for the throttle isn't moving. It is probably stuck from gum buildup inside the carb throat. If you have some spray carb cleaner spray some in the carb throat with the engine off, work the rod back and forth. It will loosen up and work well again. This engine has sit for a while and needs breaking in again.
B

Answer 2

Sounds like something to do with the governor.