If your mag. is down front then it is the later starting engine & the throws on the crank are opposite or 180 D. apart where with the early engine both throws are on the same side & have a counter weight as part of it.The mag. on this early one has it on top of the front cover standing up & the cap & wires pointed up in the air.

I have always been told that when they changed to the one piston up one piston down the engine was a lot better to start by hand.
tctractors,

TC, there might be a little something to that but I doubt if very many crank them to start them since they have the electric starter on them.

Were the pony motors the same dimensions for all the D7's and 8's like the D2/D4 pony that I have been told was the same basic engine from the very first RD4 on through the late 50's? Just peripheral things like exhaust manifolds etc changing through the years?

CC yes the D7-8-9 tractors all used the same starting engine along with many other larger industrial engines like the D337 & D326s & D343 & the big Vs D386 & D397 D364 & D375s etc.

Years ago when dad had the business, we had 4 DW21's and 2 D8'S all with the same general pup engine. I would try and convert any machine to the vertical mag model of pup, if it didn't already have it, using our spares. I found they seemed to start and run better, fire evenly, never weak on one cylinder. The horizontal mag seemed to have a weak rotor also. I changed the cam, crank, timing cover, governor, and mag on one engine to convert it. Under load the horizontal mag pup would have the same power though, if#2 plug was firing alright. I've always wondered why Cat built that oddball firing unit with 2 cylinders firing so close together. Just my opinion. Phil

S.J. I would love you to try starting my Donkey/pony motor with any form of gizmo, the only way is hand crank, as there is no place for a starter motor, when I was only a pup myself it was still common to start these engines by hand ,
tctractors.

TC the starting engines discussed here would have starters on them but as you mentioned I know lots of the older starting engines were hand crankers & have had to start lots of them that way, the old D7 & 8s. The old smaller D2-4-& 6s you used the old rope to crank them up.

S.J. I always love to read all your postings,I would love to meet you in person as your machinery knowledge and manners are first class, but England is like the Moon compared to the U.S.A. in the past a Donkey/pony motor did not even have to work on half the tractors in the U.K.as the owners were to tight fisted to buy the petrol for them, so the cost of batteries to turn them over would be some sort of miracle , I used to often work with a real tough old boy that was a fitter for a very large Co, B. Sunley, this chap (Albert Snow ) used to work 12 hours a day for 6 days then on Sunday he had to work 16 hours, in order to swap shifts days to nights, he had the great idea of fixing 1 head light to each of the RD8 tractors so they could work through the night, these tractors were run near non stop unless broken down or in need of adjustment, if they were stopped they would be on a good slope or pushed started by another tractor, (I have the pictures) Petrol here is about $10 a gallon (Imp) most Donkey engines have somewhare to poke a starting handle in the U.K.
Always Happy tctractors

TC,

Your "petrol" costs in the UK are astounding! Whenever I get "down" about input costs like fuel and fertilizer and taxes and the like, I can always compare our lot here in the US with other places in the world. Usually get to feeling pretty lucky after a little reflection on the true state of the world.

I would expect to pay less than $3.00/gal (us) for gasoline and around $4.00 a gallon for milk. so that leads to the question of what is a gallon of milk costing in the UK? Of course with that fuel cost, the farmer probably gets less of the retail price just because of transportation costs.

Farmer probably gets around 50% of retail here. Of course retail can be anything from the "loss leader" price that gets shoppers into the store, to organic premium price, so who knows.