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Atomic Custom
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So, I have ran into this on a few motors (especially when running a Pan oil pump). Knuckles oil returns via case vacuum and when you have too much oil going up, its fairly common to not get enough "pull" to clear your rocker tins and you end up with oil puking out of your shiny new Knucklehead.

This is a fairly easy fix to meter the amount of oil going up. I do this on a lathe, but you can do it with a drill and a vise!

1. Dig into your pile of jets (pretty much any will work) and drill the orifice out to .080.


2. Bore your cam chest fitting and and tap to match your jet.


3. Install your "jet" and put it all back together!


Now you can meter the amount of oil going up to your top end.. ALWAYS check to make sure you ARE oiling! This should help your case vacuum keep up with the amount of oil going up top and leave you smiling and fairly leak free! Enjoy motherfuckers.
 

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yep, the Mule puked like crazy. i silver soldered the fitting and used an .060 drill bit.

still weeps (like me). 'fairly' is a good word

thanks for the tip.

oh yeah, my oil pump is an S&S SHovel type - ugh
 

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Trent!

I always used simple brass rivets drilled to different sizes, and merely captured them under the compression nut.
This allowed me to swap them out immediately if a different size was indicated.

.060" seemed appropriate, although I went as low as .045" on one with a modern high-volume pump and pinion ratio (duh).

Most often it was a matter of tuning to the owner's riding habits.

....Cotten
 

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Is this necessary with a stock knuckle oil pump also? Or are they lower pressure so over oiling doesnt happen ?
 

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Is this necessary with a stock knuckle oil pump also? Or are they lower pressure so over oiling doesnt happen ?
Yardman!

There were two basic designs of Knuck pumps;
The early ones were perfectly adequate, and lasted forever, but less was needed anyway,..

So they upped the ante with the governed pumps.
They are over-complicated and byzantine, and that's why I love them. And with a little common sense, they also last forever.

The governor cut back supply at higher speeds.
The Shop Dope update to be the hollow Pan pump gives more all of the time.
But then you start to get messy if you cruise on the Interstate for a couple of dozen miles or so.

Meaning the riding habit means something.

The motor was designed to recover excess oil from the top end when a vacuum from beneath occurred.
If the motor is not de-accellerated regularly, as one expects upon city streets, cow paths, and 1940's country highways,.. then it don't drain.

So one must practice the MOCO-prescribed habit of occasional de-accelleration on long straight-aways, as the Panhead was the first OHV that could have its throttle set and cruise all day.

....Cotten
 

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Cory!

The '48 pump was the 'hollow' pump, where the governor was removed, and one passage in the middle plate was blocked, as described in a Shop Dope.

I once mistakenly performed it to a '47 pump without issue, until the machine changed hands.

The Pan pump covers were typically not machined to accept a governor.

....Cotten
 
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