D6 pony motor

Anonymous-0

Well-known Member
Anyone out there have any hands on expierience with cat pony motors? I'm assembling one for a D6, I've bought new main bearings and when I install them with the oil holes and dowel pin holes lined up I have excessive crankshaft end play.
 
Interested in a complete D-6 Pony? I converted to electric. Pulled mine, with good compression, new rebuilt carb and magneto and new gas tank & lines. On a pallet in my shop.

Wayne in Virginia
 
I hav'nt got to that washer yet. As I said when I line up the oil holes and dowel hole the clearence is excessive. I can drive the bearing in further and take up the clearence, but then my holes are not aligned. I only have a parts manual, according to that all bearing numbers for several serial numbers are the same.
 
Is this one you had and tore down, or one that someone brought you, or one you never heard run before? What I'm getting at is if someone ground the thrust faces on the crank to an excessive amount to cause excessive end play.... hard telling what others have done before you got there. Most pony engines I was ever around seemed to have end play measured in inches instead of thousandths. Just my experience.
 
The washer butts up against the bearing to control the thrust on one direction. The crankshaft butts up against the other bearing to control the thrust in the other direction

If the crankshaft thrust face is in good condition the bearing can be moved and the dowel pin and lube holes can be redrilled using the housing as a guide. Drill 15/64 and ream to 0,249-0.250 for the dowel.

Thrust should be 0.010 to 0.016
Max allowable is 0.025.

Another option is to make an all new bearing out of T6 aluminum that fits the conditions.
Crankshafts can also be built up to restore original clearances and fit original bearing specs.
 
Thank you oldmagnet, my thought was to drill the bearing, just thought I would ask a couple questions before doing that. Seems remotely crude, but if thats cat procedure then I will. Thanks again.
 
Long story, the engine came to me in a box in pieces. Yes, it had obviously been tampered with. I inspected the crank very closely, did'nt appear to have any prior work done. The bearing did though. Thats why I bought new bearings from cat, just trying to get as close to original spec as possible. The engine on the machine has very little end ply, but a cracked block.
 
Electric start works great. The speed that my starter turns the engine is surprisingly fast. For where I live in South Central Virgina I will have little problems with the extreme cold temperatures that concern some when thinking of conversion from Pup to electric. For me it was a good choice.
Wayne
 
What motor is the pony going on? Next week I'll be working out of town for a customer that had a factory service manual for the D333 thats in his old D6. I used it last year when I rebuilt the main engine for him and I believe it also has all of the pony motor stuff in it too. If you need something out of it just let me know, and I'll see if he'll let me bum it off of him for a day or so while I'm town.
 
I see, as long as it works I'll do what I have to. Seems I had to move the bearing in quite alot though, I did'nt actually measure it, but I bet it was close to a quarter inch. Why so far off with original cat parts? I have no known history of this engine so I suppose it could be a mix and match from years past.
 
Thanks NCWayne, that would be great! I think OldMagnet got me on the right track for now, although I may need other info as I go. I see a few posts on here about mag timing. Sounds a bit tricky maybe, I guess I will find out soon enough. This is a little side project though, so I'm not setting any speed records.
 
P.S. NCWayne, mine is a D6-8U. I'm really not sure what the main engine is. I did hear a small rumor that most pony motors are the same. Not sure, just something someone said recently.
 
Crank thrust face looks fine. If the pony motor is exclusive to the D6 series, I'm now wondering if this motor is from another series and that would explain why my new parts seem so far off. I should do just a little more research to make sure it will fit the machine properly. Souds like you have alot of expierience with these.
 
Crankshaft part number did change from 4B2311 to 5F8405 but I don't know of any specific changes. Rest of the pony basic engine is the same, early or late. Just some of the bolt ons changed.
Yes, pretty familiar with the D6-9U's of which I have two. One is pony motor, the other direct electric start.
Not unusual to find crankshaft end play pretty far out of spec but 1/4" is pushing it.
 

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