I have a LX277 tractor with a Kawasaki 17hp twin. The problem I'm having is the engine bogs down under load. Seems to run fine otherwise. I've replaced the fuel filter, spark plugs, sharpened the blades and cleaned and grease the spindles. So far nothings helped. Any suggestions?

Run some combustion chamber cleaner directly into the carb. It is much better at cleaning clogged jets and orifices than commercial carb. cleaner. Pour in slowly at high idle while it is running. It will smoke like crazy. Bog it right out with the pour then let the machine sit for an hour then run the engine fast to complete the clean. Hope this helps!
Rob