Priming the Cub oil pump

Dave H (MI) · Jan 4, 2011

So about this procedure. Did a little sniffing around and came up with the following:

Squirt oil into the top hole in the oil filter canister until you start seeing oil coming back in. Does it come back in the hole I am squirting it into or the bottom hole? Nothing is coming thru the bottom. MIGHT be coming back in the little hole I squirt into but who can tell for sure? I might just be spilling it over. Any tips or advice? I'm ready to pull the starter!

Janicholson · Jan 4, 2011

There is a hex key (allen wrench) plug behind the filter on the block. Remove it. Put a pump oil can into this hole with a short piece of rubber hoes or other adapter to squirt oil into this hole until there is resistence to pumping (it might take several refills of the oil can.) this primes not only the pump, but the gallery and lifters/cam rods. Jim

Dave H (MI) · Jan 4, 2011

Is the rubber hose used to make a seal? Otherwise I assume there would be no resistance?

Janicholson · Jan 4, 2011

YEs, it is just to (kind of) adapt the oil can spout to the threaded hole of the gallery. It works well, and gives instant oil pressure. Cubs have the oil pump built into the block, abd it is rather high. As a result they can loose prime, and also be difficult to prime. This makes it work, and provides instaqnt Lube for the bearings. Jim

Dave H (MI) · Jan 4, 2011

OK thanks! I'll have at it.

Challenger · Jan 4, 2011

I haven"t tried this yet but I think the push down oil pump that is used to fill the lower transmission drive on outboard motors might work on the Cub. I think the connector on the hose to the pump is the same size as the plug that is on the Cub. Just a thought.

Check out an auto parts store for the pump which has the hose and thread-in adaptor. If you decide to check it out, let us know if it works.

Dave H (MI) · Jan 4, 2011

I have to admit that I am scratching my head as to what exactly I am trying to accomplish. Looked at a lot of pictures and read all I could find. Would appear that I am trying to fill all the oil ports from filter to pump with as much oil and as little air as possible...but still not real sure. Took a little under the weather this afternoon so never made it back out there.

Janicholson · Jan 4, 2011

Your concept is correct. If every oil passage is filled, including the pickup tube to the pump, it will have pressure immediately when started. Many people pack the pump (especially on a Cub engine) with Vaseline to assure solid vacuum to the pickup strainer.
When the air is all shoved out of the small passages. the resistance on the pump will go up (you will feel resistance when pumping) Jim

Art Massing · Jan 4, 2011

Dave,
The allen head pipe plug is on the back flange of the block on the same side as the pump (left side as viewed from behind the tractor). I’ve attached a picture and description.

Hope this helps.

Good luck,

Art

Dave H (MI) · Jan 4, 2011

Thanks Art! I think I know enough now to get myself into trouble...

Priming the Cub oil pump

Dave H (MI)

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Janicholson

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Dave H (MI)

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Janicholson

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Dave H (MI)

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Challenger

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Dave H (MI)

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Janicholson

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Art Massing

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Dave H (MI)

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