I used my 1997 Craftsman tractor with 15.5hp Kohler engine all winter for plowing my steep driveway. The first time mowing I began to lose power and (even with the moer deck off) it now barely moves up any incline. The air and fuel filter are fine an the oil is freash and full... any thoughts?

Do a compession check and come back here with your numbers. Could be a stuck valve or burned ring.

Yes check the compression.

I believe the compression is fine. Further analysis shows that once the tractor has been running a while (less than half an hour) is when the power loss occurs. THe engine does not appear to be overheating and does not stall or idle badly... simply no drive power. The drive belt is in good shap and does not appear to be slipping.

Humor us, this may end up as a process of elimination and a compression check is the most likely place to start.

I have checked the compression and it is 75psi, cold or hot engine (when power is lost).

Does the ngine reach full RPMs when not under a strain? What happens to RPMs when you engage the blade?

Engine RPM does not drop, even with the blade engaged. The mowing blade has no effect on the problem, even if I let it heat up without the blade, it loses power. For information, is the 75psi a normal compression?

So your engine continues at the normal full throttle RPM but you loose speed, this must be s belt slipping. Have you checked the drive belt tension and adjusted?

I am thinking that the belt is getting hot, and is either glazed, or is stretching.

Thank you for all of your inputs, but the saga continues. I have replaced the drive bely and have checked the idler pulley and tension pulley for proper operation (free spinning). In addition, the tension springs are fine.

After replacing the belt I drove the tractor and the loss of power returned.. again after 1/2 hour or so. Seems to me that the hydrostatic transmission is getting very, very hot (too hot to touch). Is this normal and if, not, is it possible to add oil to the tranny?

I have not checked the rpm for compression nor have I checked the belt yet, but I know that the battery I am using is bad and needs replacement. Thank all of you, you had very good points and have given me a lot to go with. I am very impressed with the lot of you and this website. I will let you know the results here shortly. :D

Try checking the float on the carb mine did the same thing. Mine was an electric actuator at the bottom of the bowl. Unplug wire and unscrew it. A few taps on the bench and then it was working again. Hold the body of it on the negative post and touch the wire to the positive post of the battery. Make sure all gas is wiped dry from it first.you should hear or see the plunger moving, if not give it a few more wacks on the bench to free it up. If it still doesn't work, the coil in it may be bad.and get a new one. Hope this helps