Oil Pump Gears & Rotor

[billpedalino]

I'm running an early panhead pump on my 1947 FL. The difference between this pump and the correct knucklehead pump is the larger feed gears used in the panhead unit. My question is if anyone is using the panhead pump in a knucklehead and if so, does the increased oil flow supplied by the larger gears cause over oiling?

Also, in the 1960's and 70's it was common practice to remove the oil pump governor/rotor from the end housing. While I'm still running mine, I don't remember the logic as to why these assemblies were generally not used - we just took them out because they "caused more problems than they're worth". Being older and (hopefully) wiser now this sounds like a chopper motor mechanic's blatant proclamation or other myth and I'm wondering if there's any validity or substance to it. When I built this motor I included the rotor thinking hat it was used for a long time throughout the 1940's and apparently worked and thus far, it hasn't appeared to have caused any top end over- or under-oiling problems. Does anyone remember why this was done??
Thanks...

[Rubone]

Bill, the rotor was a pressure moderating bypass assembly and was eliminated on Pans when it was determined that they needed ALL the oil they could get on start-up to pump up the lifters way out on the end of the line...

[billpedalino]

Bill, the rotor was a pressure moderating bypass assembly and was eliminated on Pans when it was determined that they needed ALL the oil they could get on start-up to pump up the lifters way out on the end of the line...

Thanks Robbie.
OK - so the range affected by the rotor is between idle RPM and the RPM where bypass starts determined by the bypass spring setting. Therefore, if over-oiling resulting from eliminating the rotor was to occur, it would happen in that range. Have you encountered any over-oiling resulting from eliminating the rotor? My interest in doing so is to lessen the shear force imposed upon the oil pump drive key.

[bobphd]

I run 2 47s without the rotors and have no issues. 1 is a sifton vtwin pump which I assume has the larger feed gears and have around 25 thousand miles on . The other is an original 47 or 48 pump I believe and I only have about 7 thousand miles on it. I am currently building a 46 motor and the pump I have for it is a 50 or 51. It has the larger gears and no rotor. Years ago I ran 1 of the 47 motors with a late shovel head aluminum pump for many years and thousands of miles and never had over oiling issues. Bob Patna

[billpedalino]

Thank you Bob. I have about 400 miles on my '47 running the panhead oil pump with the rotor and I've had no problems running the rotor. I removed the pump last week to once again attempt to address the usual check ball/wet-sumping issue. Whth the pump removed I decided to delve into the old rotor vs. non-rotor issue one last time before I reinstalled the pump. To this day, I still don't know what the older mechanics had against the rotors back then. In any event, my rotor seemed to work well so the pump is back on the bike with the rotor installed.

Thanks to all for responding and Happy New Year!

[eongaro75]

Hi Guys
interesting Topic, i am looking to restore my 47 knucklehead, but now my oil pump has installed one 1950 pump cover, not correct but and run well.
my idea is to replace the cover with one original code 682-41 but i not understand if the Rotor 687-41C is necessary or not.
i have read on other forum that is possible to install this cover without rotor, it's TRUE ?

From Palmer and Services manual 40-47 Big Twin is indicated like necessary, but the pump can work without this ?

Thanks a lot for your support
Enrico