720 rear pto issues

I have done a repower for a friend of mine, adding a 25 hp Kohler command motor, to his Allis Chalmers 720 Garden tractor.
I have made, or have had made, all the mounts and brackets to make this work.
Both front and rear pto's have been hooked up, and work. Or should I say, did work.
The front has worked very well, and since attaching the rear pto, it has worked like it should with nothing hooked up.
My friend just bought a 48 inch, 2000 rpm John Deere tiller, to do his garden with.
It worked flawless, half way across the garden. It started smoking, and before he got the cover off, there was a small fire. Nothing damaged, but just very hot.
I don't know what caused it to get hot.
Did increasing the horsepower, cause an increase in amperage or voltage to the rear clutch, to cause it to burn out.
The original engine was an Onan, rated at 18.5 HP. the Kohler, is a 25 HP engine. I had read in another forum, that when repowering, and going with a larger HP engine, you can't use 100 percent throttle. I've read 65 and 75 percent.
Can the clutch be rebuilt?
Does anyone have a replacement for sale. The rear pto is totally different from the front.
Please any help would be appreciated.

Was the oil level checked? Hal

Sounds like just too much HP for the clutch to
handle, started slipping and burned it up.

Not familiar with your particular model, but
electric PTO clutches are used on a lot of
commercial mowers. Might do some window shopping,
find a model with a 25 HP or bigger motor, take a
look at the clutch and see if it could be adapted
to the 720. The larger capacity clutches will have
an 1 1/8" bore.

Also be sure the switch and wiring are large
enough to deliver full voltage to the coil. Any
voltage drop is going to result in loss of
gripping power of the clutch.

On their smaller mowers there was an air gap listed for the clutch, if it was worn too much that may be the trouble.

(quoted from post at 21:26:53 06/01/14) On their smaller mowers there was an air gap listed for the clutch, if it was worn too much that may be the trouble.

Click to expand...

The front pto clutch does have an air gap, and it's worked fine for over 6 years with the motor swap, and using the 60 inch mower deck.
The rear pto is a differend bird from the front, and I don't think there is a way to set the air gap.
A drive shaft bolted to the flywheel, goes back to one side of the clutch.
The back half of the clutch, bolts directly to the gear box for the rear pto.
A chain master link, connects to the front part of the clutch, and is secured, so it doesn't rotate.
I noticed that on John Deere's larger garden tractors, there is a fan directly in front of the clutch. I'm not sure to keep debris off the clutch, or to help cool it or both.
I've scoured the internet, and haven't found another rear clutch assembly for this application. Maybe another kind can be adapted, but will take some engineering, to get it to work.
There is limited space where this clutch is, so a larger clutch probably won't fit.