Grasshopper 720K Loses Power Mowing Uphill and Tall Grass

[JaoeyP]

So, I've recently bought a 98 Grasshopper 720K, with Kohler CH20S motor and 61" deck. I have replaced the fuel lines, fuel pump, gas tank (old one leaked), head gaskets (one was blown, and spark plugs. I've also cleaned the carburetor, changed the motor oil, changed the hydro oil, and the ALL the filters (oil, hydros, fuel, and air).

The motor starts easily and seems to run great. Without the blades engaged I can run the mower as fast as it will go, no problems at all. With blades engaged it runs well on enough on flat ground but the motor really bogs down mowing uphill OR if I'm trying to cut taller grass (stuff that hasn't been mounted in 2-4 weeks).

PTO engages well, 3 points on drive shaft are greased (manual says to do so every 8 hours).

Mower has mulching blades on, but I can't think that's causing the uphill issue (although may really be contributing to the tall grass bog down).

I really don't know what else to check here. Spindles all seem easy enough to spin, idlers seem in good shape. I don't know how to check the 90 degree gear box, but it turns easy enough by hand.

Am I just expecting too much of the 20hp motor?

Machine has 490 hours.

It does have a leak at the rear main seal (new seal is in, will fix next weekend).

Any ideas?

 

[bertsmobile1]

Put a little bit of string on the governor arm
When going up hill pull the string to open up the throttle butterfly a bit more.
If you can & the mower picks up then the governor need adjusting or the spring needs replacing
IF the throttle is already fully open then you are flogging a dead horse .

 

[JaoeyP]

Okay, I feel pretty silly here. Got the deck lifted, my blades were in pretty rough shape. I could see the right blade was pretty dull and needed sharpened, but each blade was progressively duller than the right. That left blade was BAD. I decided to try sharpening before pouring more money into the mower. Got them all good and sharp, made sure they were balanced. Mowing great now. It slows a little up hill, but doesn't completely bog down like before. For your viewing pleasure, here is a pic of that left blade. No wonder I was bogging down, sure was a lot of load on that engine to mow with this.

 

[MParr]

Imagine how a new set would perform! Try OEM style blades. You will see a big improvement.
I won’t run a Gator style blade until fall cleanup.