kludge
New member
I wanted to share a modification that I have made to my PT425. The initial reason I had for adding an extra cooling fan is an unseated valve and bent push rods. The earlier PT425's have the front of the Kohler engine down in the box at the front. This location on mine wasn't able to pull enough fresh air through the engine. The side benefit that I have enjoyed has been the icing on the cake for this mod. With the extra fan blowing down into the box, the positive air pressure keeps the grass clippings from being sucked into the engine box area. I haven't had to clean the front of the engine off after mowing.
Now for the details. First I ordered another fan. I went ahead and used the same SPAL fan that is on the oil cooler. It draws around 6 amps. I had some concern about the alternator being a 15 amp source. After talking to the small engine shop whom I had replace the valve seat. They were of the opinion that the alternators almost always supply more current than advertised.
Next I had to build a box to mount the fan in. There was not enough space to mount the fan flat. I cut a 6" x 11" hole in the top of the engine compartment cover. Mounted the fan and box upright on top of the cutout.
I tapped the wires for the oil cooler fan before the temperature switch.
Finally I used flashing to close off the front of the engine compartment cover and 10" back on each side. Under the cover I added a flashing panel extending from the top down to the top of the air filter cover. This had the effect of channeling the air from the fan down to the front of the engine. Activating the fan I could feel airflow coming out the back of the PT425 near the bottom
The one drawback that I have run into so far is that when the oil is hot and both fans are running, there is barely enough amperage to crank the engine. I haven't decided whether to change the battery to one with a larger cold crank capacity or simply add a normally closed pushbutton switch to the circuit to act as a temporary fan kill switch for cranking.
Now for the details. First I ordered another fan. I went ahead and used the same SPAL fan that is on the oil cooler. It draws around 6 amps. I had some concern about the alternator being a 15 amp source. After talking to the small engine shop whom I had replace the valve seat. They were of the opinion that the alternators almost always supply more current than advertised.
Next I had to build a box to mount the fan in. There was not enough space to mount the fan flat. I cut a 6" x 11" hole in the top of the engine compartment cover. Mounted the fan and box upright on top of the cutout.
I tapped the wires for the oil cooler fan before the temperature switch.
Finally I used flashing to close off the front of the engine compartment cover and 10" back on each side. Under the cover I added a flashing panel extending from the top down to the top of the air filter cover. This had the effect of channeling the air from the fan down to the front of the engine. Activating the fan I could feel airflow coming out the back of the PT425 near the bottom
The one drawback that I have run into so far is that when the oil is hot and both fans are running, there is barely enough amperage to crank the engine. I haven't decided whether to change the battery to one with a larger cold crank capacity or simply add a normally closed pushbutton switch to the circuit to act as a temporary fan kill switch for cranking.