Pony Motor Model Specs on 1959 D7C with D-339 Engine

The d7 carburator is ZENITH CARBURATOR and am still have some used carb. and poney parts and you could get a kit from CATERPILLAR

your parts book for your D7 serial # will have the pony motor parts listed.Also your operation and maintenance manual will also cover the pony motor

Thank you. Where do I find the correct operation and maintenance manual?

Also, was at CAT site, and entered my serial number, 17A10407, and the site replied they had no record of that serial number. Please advise.

Thanks, Jim

Everyone has given good info regarding the pony motor. It has no model number or parts book etc if its own, but is included in the D7 17a. books.
Just for your information, it is a 3-5/8" bore x 4" stroke 2 cylinder upright engine that produces 25 Hp at 2700 rpm. There were a few changes somewhere along about the 17a's that had the pony and main engine sharing the same oil. Most of those were converted back to separate after it was found to severely decrease life of the pony. Another change that was temporary but could not be changed back was an even fire crankshaft and magneto to match. The original design is basically half of a 4 cylinder so it is an odd fire design which is obvious when you look at the mag cap with two terminals over to one side and blanks opposite them. For a short time, CAT produced an even fire design but soon went back to the original odd fire design. I expect the crankshaft design had something to do with the change back, but that is just a guess.

If it has the cast iron up draft carburetor like the D7e, its not too hard to disassemble and clean. I think I had to make one gasket that goes between top and bowl. On the cast iron carbs, you really need to ream the passages with a drill bit. Of course stay off the jets and needles, but the cast iron rust and old gas can really plug one up. This may require drilling out lead plugs, but I think a lot of the passages are accessible after you disassemble the carb.

The smaller horizontal opposed cylinder pony motors on D2, D4, and D6 use a zenith TU4C downdraft carburetor and requires drilling out lead plugs for most of the passages to properly clean it. I have never heard what model the pony carb on the D7, D8, etc is, maybe it is a CAT design???

One other point, I thought the 17a's were the D7d. I think that was before much was made of the letter series of the various tractors. I know the D7e 48a says series E on the serial number plate.....never saw that on anything older, though the D6 b was apparently designated as such when it was introduced in 1960(date???).

Mcdonald carb and ignition is a good source of parts. Can order from them online.

Cat Carburetor Designations....