Hello again all

Got another joyful question for you,
I have had my crankshaft ground so I’m of course going to use undersize bearings
BUT
do I also need to use undersize crankshaft seals?
If so I will need part numbers etc

On a side note, I imagine I am not the only one looking forward to watching squatch253 start building a donkey engine for his 5J

"Neil" wrote:

Great question - when I did both of mine (5U and 3J pony engines), I didn't think about the seal size so I'm glad you pulled up this question. Mine are 030 I think but they don't leak and have the standard Cat part # seals in them

Hmm interesting, i will definitely make a note of that.
Hopefully someone on this group will be able to shed more light on the topic

Are the U donkeys any different to the J donkeys? Obviously things like electric start

Thanks great info to know

Take the spring out of seal, unwind the spring, cut off a couple of rounds of seal, then screw the seal back together. This will tighten the seal around the shaft a little tighter.

Exact same basic donkey motor, just subtle changes to the bolt on stuff like upper manifold and heads over the years and models, none of the Parts Number books lists a seal for undersize cranks to go with the undersize bearings, so I assume Cat didn't think it necessary.

If you were running the pilot motor 8 hours a day I'd be concerned, but generally they are lucky to run 15 minutes max, most times 5 minutes, can't figure much oil could be lost in that time past the seals.

Somewhere I have a book with seal sizes .