I need some help. I have an older Ferris ISZ 61" deck with a Kawasaki 23hp engine. What is happening is that after 5 minutes, when the engine has warmed up, of load (blades engaged) the power drops off significantly. To the point that the engine almost stalls. When I disengage the blades, the motor revs right back up. Also, the engine has developed a backfire when I back off the throttle. Here is what I have done so far:

1) Rebuilt the deck (New spindles, pulleys, spring, belt, blades)
2) Rebuilt the carburetor
3) New fuel pump
4) New battery
5) New electric clutch
6) New plugs
7) Good compression
8) New muffler
9) Good fuses
10) New fuel filter (Installed correctly)
11) New and correct air filter

From this point forward, I don't even know what to look at?

Could it be a sticking valve, dirt in the fuel system, clogged exhaust, a bad hydraulic pump??

Please HELP.

David

We had this problem with a Kawasaki on a Scag mower. The engine had been rebuilt in Kentucky and had never been right since the rebuild. Needless to say the shop in KY was not very helpful to the owner and he heard about us, so he came to us with the Scag unit. We spent a lot of time on it, and it got to where we said, Okay, we aren't even going to charge anymore for labor over the first hour and we had at that time stayed and spent about seven hours on the thing. We completed many different test procedures and finally gave up and went home about eleven p.m. We worked on it some in between other jobs when we would think of something else to try, and never did figure the thing out to where it would run at a smooth idle, and a high rpm under load. We could make it work but not exactly correctly. The thing blowed our minds. But we finally got it to where the owner was happy. So what I am trying to say here is, best wishes, the Kawasakis are good engines, but can be hard to figure out exactly sometimes.