Engine Conversion PT-422 to Predator 670

Predator Trac · Oct 28, 2015

Hi Everyone,

This is my first post here and I though you guys might be interested. At 104 hours on my just over one year old 422, my Robin decided to stop cooling on one cylinder and subsequently tossed a rod, welded the piston to the cylinder.....you know how that goes. Power Trac couldn't help and Robin refused a warranty claim after keeping my machine at a service facility for two months. After that crap, I decided to switch engine brands and re-power it myself.

Being fully aware of potential quality concerns, I bought a 22HP Honda knock off from Harbor Freight for $600. The bottom mounting holes and pattern are identical to the Robin. The PTO side mounting holes were slightly different for the pump mount, so that had to be slightly modified. The Predator shaft is 1in opposed to the 1 1/8 on the Robin...a new lovejoy fixed that. I had to cut off a chunk of the driveshaft and space out the pump mount, but everything fits, however pretty tight. I did not have to modify the frame or cover to accommodate anything. I had to cut and weld the exhaust flanges at 90 degrees on the original muffler, but that fits nice now too. The existing controls for throttle, choke, and start all work as they used to and the wiring was simple to deal with.

The new engine, out of the box had a bad ignition coil. I replaced both coils, since I was in there, with aftermarket coils intended for a Honda GX660 and everything works. Attached are a couple photos of the result.

There is nothing too exciting here, but I though I should share this with the community.

Unionspring · Oct 28, 2015

Predator trac,

Nice work. I hate to hear you had to do such major work on an essentially new machine. I wanted to ask; up to this point in ownership how did you primarily use your machine? Was it to mow or basic loader work. Did you have any warning signs of a possible future problem? I wish you the very best in the future of your newly powered machine. I know I love my 422 though it only has 7 hours to date.

Predator Trac · Oct 28, 2015

Unionspring,

I would guess that over 90% of my hours are spent mowing. The remainder was moving snow and loader work. I think the mowing is what did the engine in. When is was disassembled, there was grass packed everywhere inside the covers. There was no warning sign of impending failure. It did not burn or leak oil.....in its last minutes it started to run rough and that was about it. It is a handy machine, best of luck.

MossRoad · Oct 28, 2015

Welcome to TBN! :thumbsup:

Nice job on the engine swap. I rotated some of the pictures for a better viewing angle.

stray · Oct 28, 2015

Where is the battery mounted?

Predator Trac · Oct 28, 2015

stray said:
Where is the battery mounted?

It is right where it used to be under the gas tank on the side opposite the muffler.

Marks481 · Oct 28, 2015

Predator Trac said:
View attachment 445480

Nice job on the installation.

Just one recommendation: where you have the oil cooler mounted, the exhaust manifold and muffler are going to heat it up. I mounted an oil cooler there on my PT422, and found out it made things worse. Just the radiated heat from the exhaust manifold will heat up the edge of the cooler to 300F+. You can run longer hoses, and put it the oil cooler on the other side.

Recommend you buy a $25 infrared thermometer, and take some shots of the oil cooler after you have been running for awhile and check to see if it is a problem.

I recognize the bottom of that machine in the background, I have a Tormach 1100 in my garage too.

Predator Trac · Oct 28, 2015

Tmarks11,

Thank you for the advise. I will look at the temperature tomorrow. Good eye to pick out the 1100!

Bigger mike · Oct 28, 2015

I run a 2003 and a 2011 pt 2425' and a smaller old one 422? I saw your tracked machine and have to know more about it. Living in the home of the Packers ( Green Bay wi. ) it's cold and snow half the year, thus the interest in tracks. I dug around and havnt found anything about it. Is the track system an aftermarket product? Any help would be appreciated. P.s. The robin engine in my 2011 is a super-duper pain in the rear. We use our 2003 with the kholer. Engine most of the year. Won't start when it's cold and over heats in the summer. Being the work horse for my tree company it has taken more than its fair share of serous abuse and keeps going, the kholer that is. I would give my 3rd born to find out what engine swap would work for the 2011 robin!!! A B R we say: "anything but robin" The bird, robin is our state bird here, starting to hate them just for the name- robin! Sorry birdies. I have to know about the tracks, I'm smiling just looking at them, thanks - bigger mike

Predator Trac · Oct 29, 2015

Bigger mike said:
I run a 2003 and a 2011 pt 2425' and a smaller old one 422? I saw your tracked machine and have to know more about it. Living in the home of the Packers ( Green Bay wi. ) it's cold and snow half the year, thus the interest in tracks. I dug around and havnt found anything about it. Is the track system an aftermarket product? Any help would be appreciated. P.s. The robin engine in my 2011 is a super-duper pain in the rear. We use our 2003 with the kholer. Engine most of the year. Won't start when it's cold and over heats in the summer. Being the work horse for my tree company it has taken more than its fair share of serous abuse and keeps going, the kholer that is. I would give my 3rd born to find out what engine swap would work for the 2011 robin!!! A B R we say: "anything but robin" The bird, robin is our state bird here, starting to hate them just for the name- robin! Sorry birdies. I have to know about the tracks, I'm smiling just looking at them, thanks - bigger mike

The tracks are a fun concept that is a couple projects down my list, but stay tuned on that one. It is pretty easy to swap out for a cheaper engine. Let me know if you want to know more or need any help.