D4 7U Pony Manual or Schematics

Doing some maintenance on the pony motor and wondering if anyone has a copy of a manual or schematics of the internals? Trying to understand what maintenance I can or cannot perform with the pony still in the tractor.

Or maybe pulling the pony and putting it back in isn't too much of a project? I have an understanding that there are 8 bolts holding it down, but unsure if I have to remove the firewall or if I can remove the bolts and pull straight up?

Would appreciate any help or advice.

I think you need to removed 9 or 10 small bolts for removing the pony on 7u and you have to removed the firewall and he has a gear under

In my opinion it’s somewhat difficult to remove and reinstall the pony. You can tune it up while in place. Remember the coolant from the big motor circulates thru the pony. I have no clue what maintenance you are doing, but hopefully you can do it while in place. Squatch 253 on utube has detailed info on this. Good luck sir

Thank you guys for the info

Having looked closer at the project, I see that it definitely requires removal of the firewall and quite a bit more accessories that reside over the top. Definitely will try to get things done in place because maybe pulling the pony will be right before I replace with an electric direct start. I just really like the pony when its cold around zero and need to start the tractor to plow snow. Never been a time that it won't start, just takes a bit more time to build up the heat.

Keep the pony on there you may need it during colder weather, you can add a electric starter and it won’t affect the pony.

I guess I never considered that, but I could have the best of both worlds as long as I found a place for the batteries other than where the pony is located. Thanks for the thought, now I have even more to consider!

Clayton has the right idea IMO. Unless your pony is worn out, leave it alone aside from some good maintenance. It isn't overly difficult to remove, but why mess with anything if it isn't broken? I have had DE added to several machines, and retained working pony motors. It is nice to have both worlds. Some folks don't appreciate having an easier way to start a machine sometimes! LOL. My D2 already had a factory hole in the bell housing, so that helped make things easier for my mechanic. He had the starter freshened up and to be 12v, so we could keep using the electric starter for the pony without getting complicated. Gas start ponies can be fun, but it tends to get old lugging around oil and gasoline to start so many here. JM

Unfortunately the reason I'm working on my pony is that mine took some teeth off the magneto gear and bent the shaft. Second time its taken out a magneto, last time it sheared off the shaft so that was really straight forward. When it happened this time the pinion clutch gave a big jerk so I have to figure out where those teeth went since I could only find one up top. Definitely do not need those pieces messing up the diesel flywheel so going to have to pull the pony so I can access things and make sure I get as many teeth as the gear is missing.

Sometimes strange things happen and two complete running pony motors showed up in the classifieds today and close enough to make the drive so may be swapping a new pony in or robbing the new one of better parts to freshen up the one I have. And considering each are priced lower than the rebuilt magneto I sourced, I cannot go wrong by picking up the better one.

I did notice the one without electric start in the pictures has the pony motor exhaust routed to the diesel exhaust manifold, mine runs through the diesel intake, but luckily it looks like the connection is the same on top of the pony so I can use my exhaust. Was there a reason for this that I can't think of because I know why mine is routed the way it is?

The earlier models routed through (around) the intake as well, the difference is that the intake and exhaust manifolds were on the same side of the engine. With the U series, they were on opposite sides and the intake routing was/is different. I have a 6U with the same routing as yours. Swapping pony engines sounds attractive - check the pony crank end play, that could be the source of your current problem, and would require a rebuild if it is excessive.

as it has busted the mag gear it needs new bushes on the crank they have flogged out. that is a remove and do on the bench job. they are only held by dowel pins and they can shear. this play creates a harmonic vibration that shatters the gear.

neil one of the other members did a post a few years back of what he did to his d2 pony(same engine)he had his tame machinist make bronze thrust washers for the crank and the engine case so instead of wearing on a aluminium/tin alloy bushing that is only about 1/4 inch thick wall it now had a nice half inch all the way round to rub against the bronze is a tougher material.

a old dozer driver told us to help prevent this flogging out wedge the pony flywheel with a couple pine wedges when it not in use just to take the weight off the bushings.

they run the exhaust on the u series machines into through the main intake and it acts like a glow plug. important to keep that exhaust covered when not using the machine or it can rust out and you will dust the main engine. it can also prevent the main from starting if that pipe is leaking into the manifold

yes the broken teeth will be down with the pinion shaft. no it wont hurt the ring gear. but can damage the bearings/driven gear on the pinion shaft. that where most of em wear on our machine.