Jim’s 720 Pony Motor saga
First I have some questions about the pony motor:
-Do pony motors have an oil pressure switch? The schematic shows one, but I have not found one on this pony motor. It is from a low serial number 720.
-I would like recommendations on the rebuilding of the water pump. The seal is still available but I am apprehensive about performing the rebuild. Suggestions? Water is getting into the pony motor oil when the pony motor runs but not when the diesel runs. I removed the pony motor water pump, put it in a vise impeller up so I could cover the impeller with water. I rotated the pump by hand and let it set. I rolled up a paper towel and put it in the weep holes. It has some dampness from the weep hole that exits to the exterior of the pump. I am guessing this is the source of the water. I did not notice leakage from this when the motor ran but I didn’t know it was there and there was a lot of oil and dirt around the base of the pony motor.
-What oil is recommended for the pony motor? I figured a 15W-40 which is what I figured to run in the diesel but I have seen recommendations for maybe 10W.
-Does anyone know of a good source of pony parts or maybe a salvage pony? I know the easiest and probably cheapest direction is to go to electric start but I really like the pony system partially due a 720 pony start that a late friend use to let me run.
-What are the recommended tappet clearances?
-My nephew is also interested in going to a narrow front end from the aftermarket wide front end. Suggestions on where to find one?
Now here is the saga for your entertainment:
My nephew bought a 720 diesel that had recently been started after setting for numerous years. He plans to use it for his pumpkin patch and Christmas tree business. The pony did not run so the diesel was pull started. From the condition and the little info received from the previous owner relatives I am guessing the pony had not run in 30 years. The diesel ran OK but it ran out of fuel and we found the sediment bowl and shut off valve completely plugged with fuel that had turned to putty. The diesel had been running on the fuel in the filters. We cleaned this all and the diesel ran fine.
The pony starter would run but not engage. We removed the starter and fixed a problem with the bendix, dumped some gas in the carb and spun it over. No luck. My nephew had other things to do so I took the pony on as a project.
My goal was to spend the minimum possible to get it running and determine the cost to get it in good shape. There was no spark so I checked the coils and determined both of them were bad. I then wired up four 12 volt coils separately from the tractor electrical system and powered the system with 12 volts. I used 6 volts for the starter. I got the plugs firing, dumped some gas in the carb and got it to pop. I removed the carb and determined it was a mess. I drilled out the lead plugs and cleaned out all the passageways which were plugged with corroded aluminum. I also got a main jet from a Cat pony from a salvage yard. I got it to sort of run but the Bakelite points did not like the 12 volts and one of them fell apart. I adapted a set of Ford points for the failed set and hooked up a Ford condenser in addition to one of original condensers. I got the pony running up to governor speed but saw the other points were smoking. I hooked the ignition up to the 6-volt battery and the pony ran fine. I then attempted to engage the pony with the diesel decompressed but all it did was grind. I found the clutch was stuck. On a whim I engaged the pony gear into the flywheel gear and with the diesel decompressed, started the pony which also rolled over the diesel. The pony came up to speed, I pulled the level fully in for the pony clutch and compressed the diesel and it started. I did this a couple of times and then the other set of points fell apart. I decided it was time to get new points, condensers and coils. After I installed these the pony would fire up fine. I then pulled the pony clutch in partly and compressed the diesel in an attempt to break the clutch lose. No luck at this. I also determined water was getting in the pony oil when it ran. I decided to remove the pony from the tractor.
After removing the pony, I checked the water pump as stated above. I also removed the pony transmission. The clutch was rusted but cleaned up nicely. The throw out bearing looks good, the transmission turns smoothly and the one-way clutch works properly. I filled the pony transmission with diesel fuel to soak.
As I stated, I used four 12 volt coils, one was from a Chevy, one from a Ford, one from a Mercury marine engine and one of unknown origin. They worked just fine on 6 volts. I have read info about coil resistance and voltage but from what I found in this instance mixing worked just fine. Attached is a photo of the ignition setup.
First I have some questions about the pony motor:
-Do pony motors have an oil pressure switch? The schematic shows one, but I have not found one on this pony motor. It is from a low serial number 720.
-I would like recommendations on the rebuilding of the water pump. The seal is still available but I am apprehensive about performing the rebuild. Suggestions? Water is getting into the pony motor oil when the pony motor runs but not when the diesel runs. I removed the pony motor water pump, put it in a vise impeller up so I could cover the impeller with water. I rotated the pump by hand and let it set. I rolled up a paper towel and put it in the weep holes. It has some dampness from the weep hole that exits to the exterior of the pump. I am guessing this is the source of the water. I did not notice leakage from this when the motor ran but I didn’t know it was there and there was a lot of oil and dirt around the base of the pony motor.
-What oil is recommended for the pony motor? I figured a 15W-40 which is what I figured to run in the diesel but I have seen recommendations for maybe 10W.
-Does anyone know of a good source of pony parts or maybe a salvage pony? I know the easiest and probably cheapest direction is to go to electric start but I really like the pony system partially due a 720 pony start that a late friend use to let me run.
-What are the recommended tappet clearances?
-My nephew is also interested in going to a narrow front end from the aftermarket wide front end. Suggestions on where to find one?
Now here is the saga for your entertainment:
My nephew bought a 720 diesel that had recently been started after setting for numerous years. He plans to use it for his pumpkin patch and Christmas tree business. The pony did not run so the diesel was pull started. From the condition and the little info received from the previous owner relatives I am guessing the pony had not run in 30 years. The diesel ran OK but it ran out of fuel and we found the sediment bowl and shut off valve completely plugged with fuel that had turned to putty. The diesel had been running on the fuel in the filters. We cleaned this all and the diesel ran fine.
The pony starter would run but not engage. We removed the starter and fixed a problem with the bendix, dumped some gas in the carb and spun it over. No luck. My nephew had other things to do so I took the pony on as a project.
My goal was to spend the minimum possible to get it running and determine the cost to get it in good shape. There was no spark so I checked the coils and determined both of them were bad. I then wired up four 12 volt coils separately from the tractor electrical system and powered the system with 12 volts. I used 6 volts for the starter. I got the plugs firing, dumped some gas in the carb and got it to pop. I removed the carb and determined it was a mess. I drilled out the lead plugs and cleaned out all the passageways which were plugged with corroded aluminum. I also got a main jet from a Cat pony from a salvage yard. I got it to sort of run but the Bakelite points did not like the 12 volts and one of them fell apart. I adapted a set of Ford points for the failed set and hooked up a Ford condenser in addition to one of original condensers. I got the pony running up to governor speed but saw the other points were smoking. I hooked the ignition up to the 6-volt battery and the pony ran fine. I then attempted to engage the pony with the diesel decompressed but all it did was grind. I found the clutch was stuck. On a whim I engaged the pony gear into the flywheel gear and with the diesel decompressed, started the pony which also rolled over the diesel. The pony came up to speed, I pulled the level fully in for the pony clutch and compressed the diesel and it started. I did this a couple of times and then the other set of points fell apart. I decided it was time to get new points, condensers and coils. After I installed these the pony would fire up fine. I then pulled the pony clutch in partly and compressed the diesel in an attempt to break the clutch lose. No luck at this. I also determined water was getting in the pony oil when it ran. I decided to remove the pony from the tractor.
After removing the pony, I checked the water pump as stated above. I also removed the pony transmission. The clutch was rusted but cleaned up nicely. The throw out bearing looks good, the transmission turns smoothly and the one-way clutch works properly. I filled the pony transmission with diesel fuel to soak.
As I stated, I used four 12 volt coils, one was from a Chevy, one from a Ford, one from a Mercury marine engine and one of unknown origin. They worked just fine on 6 volts. I have read info about coil resistance and voltage but from what I found in this instance mixing worked just fine. Attached is a photo of the ignition setup.