Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Oil pump sump fix ?

Oil pump sump fix ?

Post Wed Oct 22, 2014 6:02 pm

Posts: 249
Location: Orlando
I am on my second oil pump body due to wet sumping a quart overnight.
I thought I saw a post here that showed the exact machining model for the two check ball seats.
I thought Mr. cotton produced the machining angles.

I want to bring one of the pump bodies to my machine shop at work but it don't have the dimensions for the ball seat for optimal closure so it will stop the oil from sumping. If someone knows where the post is, or has a sketch of the optimal ball seat dimensions, I sure would appreciate it. If it works I will do both pumps.
It seems to me the sharper the edge the better. Maybe?



Post Wed Oct 22, 2014 6:44 pm

Posts: 543
Location: Wa, USA
There have been many posts on this issue over the years. I have had good results by using a 3/8" ball mill on the end of a 1/4" or 5/16" rod and silver soldering a 3/8" carbide ball on the radiused end. I used this in a drill with fine lapping compound to lap the seat. Many have said this is not the best method, but it has worked for me. I have been able to rescue bodies that were very rusted and pitted and they worked quite well.

Post Thu Oct 23, 2014 5:14 am

Posts: 3160
Location: Central Illinois, USA

After the agony of many attempts at contour cutting, grinding, lapping, burnishing, and even smacking with a drift,...

I found that all methods only worsen a seat beyond a simple flat grind to a 'zero degree' sharp edge.

The seat is often not concentric to the plug threads or the rest of the well, and occasionally the casting is 'chilled', making it too hard to cut or burnish.

Bubbles tell all,

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Post Thu Oct 23, 2014 6:52 pm

Posts: 497
Location: Six miles East of Cheney, Wa.
I've got to 100% sure your spring is actually putting pressure on the ball. Don't ask me how I know that.


Post Fri Oct 24, 2014 8:31 pm

Posts: 249
Location: Orlando
I am grinding the top and I need to put a slight, sharp 60 degree angle on the circumference due to the hole edges not perfect. To much, and crap can get between the ball and seat.

Thanks for the help, I'll let you know how it turns out.


Post Sat Nov 15, 2014 11:17 am

Posts: 249
Location: Orlando
So frustrated, I tried the pump I modified and it seemed to leak slow until I rode it. Then it stopped. I rode again and it sat for a week and it leaked until it came out of the front chain oiler. It Basically filled the crank case.

I thought this would be the least of my problems after rebuilding the engine and transmission.

I have three pump bodies. The last one I bought was supposedly new repop.

Is it possible for the oil to leak into the crankcase through the valve cam gear that turns the pump?

Post Sat Nov 15, 2014 11:33 am

Posts: 543
Location: Wa, USA
Possible but highly improbable if the bushing has been fitted properly.

The cheapest and quickest fix for this is a manual valve in the feed line to shut it off when not running. Just don't forget to turn it on before starting. :)

Post Sat Nov 15, 2014 4:45 pm

Posts: 249
Location: Orlando
The thing is, I have tried by best to follow Bruce Palmer's book "How to Restore Military Harley Davidson" even down to cad screws parkerizing, paint, nos and restored used parts. I would hate to put a fault peculiar valve on the bike.

Post Sat Nov 15, 2014 5:14 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

Brendan, I agree with you. Keep it stock. There must be a reason for the issue that has been over looked.

Post Sun Nov 16, 2014 3:00 am

Posts: 249
Location: Orlando
I checked the vent tube and return tank tubes for leak back but they are dry. I need a known good ,or known semi good pump, that wont leak out over the course of 5 days to see if i have bushing problem.

i honestly thought I would have transmission , engine, electrical, or fuel issues when i first started her.

I took it for a ride last weekend and the only issue is the rider, I never rode a tank shifter, It might as well have been a helicopter the way I handled the throttle , shifter, brake and clutch.

Post Sun Nov 16, 2014 6:50 pm

Posts: 497
Location: Six miles East of Cheney, Wa.
Just as an experiment, why not put a long, heavy spring in there JUST to see if it continues to wet sump. ?? That would be a sure way to eliminate one or two variables. Why ASSUME that the stock spring is either long enough, or putting enough pressure on the ball?

I hear you on the shifting. I rode a knuck with a "suicide" shift, shift lever directly off the tranny, and a foot clutch, that did/does NOT stay in/engaged if you take your foot off it, for like 20 years. At one time I believe I could work that clutch and shifter as well as anyone with a hand clutch and foot shift. Then I rode a hand clutch for about ten years, then last year I put together a big twin flathead with the same clutch and hand shift set up. I thought it would be like getting back on the perverbial bicycle again. Wrong! Took 50 miles just to get somewhat reacquainted with it, to where I didn't feel like I was flying a helicopter for the first time, and 1,000 miles later I'm not quite back to where I was on the Knuck. !!! But I'm close...or at least now comfortable in city traffic. Takes a "little" practice!

Good luck.


Post Sun Nov 16, 2014 10:35 pm

Posts: 249
Location: Orlando
Knucklebolt, That is a great diagnostic idea. REALLY plug the check ball paths. I think I plug the check holes with ta couple of those rubber cones used to keep paint out of holes. Fill it with oil and monitor. Not start it.
Off comes the pump and and an experiment begins.

How much play should I expect in the throttle grip?



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