47 oil pump question

[John Guntner]

The base plate on the bottom of my oil pump is scored. How do you grind it to remove the groves? Do I have to have it milled flat or can I grind it myself somehow?

[indianut]

[John Guntner]

OK, I see how you do it. Looks like a job for,,,,,,,somebody else. Thanks Inian Nut

[sirhrmechanic]

Indianut's method is definitely correct. It's very challenging, as well, to get the plate perfectly aligned so the surface grinder can cut it straight.

That said, if your base is not deeply scored (ie. a couple of thou), you can do it at home on a flat plate with paper. But you have to be careful and deliberate.

I just cleaned up the base of my '38 pump this way. But it was not deeply scored.

Use sand paper (wet/dry, not wood-type hardware paper.) Start with 240, then go to 320 and 400. Use soapy water for a lubricant and to pull the debris away. Keep the paper very wet.

Work the piece in a figure-eight pattern (best for flatting) rather than back and forth in a straight line. And after a couple of dozen strokes, change the orientation of the piece so that any uneven hand pressure (and there will be some) won't be transferred to the part. Work mostly with the 240. The 320 and 400 are just for polishing.

If you have more than 4-6 thou wear, don't bother. Use Indianut's method and have it professionally done.

Finally, make sure that your gears are stoned flat on the bottom. If your pump bottom is scored, there are probably burrs on your gears. Use stones to clean up.

If there are a few faint scores and scratches still on the pump base, they will not terribly affect the oil pressure. As long as the gears are dead smooth.

One last thing... I found on my pump that it really helped to mark the teeth for mesh and then lap the teeth in together. Probably not needed on new gears, but I suspect mine had been used to crush rocks or chip tree branches or something. Lots of stoning and cleaning off rust and burrs. Once I had then where my fingers could feel nothing amok, I used 400 grit lapping compound on the gears and worked them in as a set. Very gently... it just takes a few dozen rotations to bed eveything together.

Took about 6 hours of work to rebuilt this pump... BUT it was seized solid when I started and I had never done one. So was very careful in how I approached it. Done tons of car gear-type pumps, though, so the processes are the same. I can post some pictures of flat-plating in some Silver Ghost pumps if that would help.

Anyway, Indianut's setup is right for a badly worn pump and is not for the amateur. But don't feel like you can't do yours. And if after working your pump on the flat plate it still needs to go to a pro... as long as you have not put it on a belt sander, you will do no harm.

Last thing... if you don't have a granite flat plate, you can get them on eBay for pretty short dollars for a small one. Or look for them at machine tool dealers. Instrument-post type 12 x 10" plates are great for small work. In a pinch, a thick glass coffee-table top is very, very flat and works quite well. But a small flat plate is a great investment. My big one (about 4' x 3') came from Rock of Ages Quarry in VT and is flat to a couple of hundreths (.00002). Nice to tool to have if you want to lap a manifold or check a big cylinder head, but a pain to move at almost a half ton...

Cheers,

Sirhr

[harleytoprock]

Sirhr gave very good advise. You can get a flat piece of 1/4 glass cut for a very reasonable cost and use that as the flat plate. If the pump is rough you can even start with 180 grit wet or dry sand paper followed by finer grit. I like to use rubber cement to glue the paper down to the glass. Just paint the glass and paper with the cement , let dry and stick them together. When the paper is worn, the paper will pull right off the glass. Any glue residue left on the glass can be rolled off by rubbing with your fingers .

[T. Cotten]

There's many ways to skin a casting, Folks!

14" Harbor Freight stick-ons, in two grits, stuck on a discarded entertainment center door is one of my favorite variations (1st attachment), but I have found that it is not as precise as the side of a large stone (second attachment).

A criss-cross pattern, rather than swirling, produces the most 'readable" finish, resulting in faces that nearly "wring" together.
A sharp mill profile is desired to hold the gasket from "walking".

Either way, the set-up time is reduced to nil, and you don't have to de-magnetize, although it is still probably a good idea.

....Cotten

[John Guntner]

Hi Sirhr,
Thanks for the excellent description. I will grind the plate and then send the pump out to check that it has the correct supply and return volumes. Thanks Cotten. I'm off to find a good flat surface. Cheers....John

[John Guntner]

Harleytoprock, Good advice. I'm now looking forward to this repair. Sounds like one a simple job for a simple guy.

[Eddie G]

I've been looking at the same thing. Who is a good source for rebuilding an oil pump?

[John Guntner]

I've been told by a very good source that John Bevins can check your pump and rebuild it if neccessary. He works with Gerry Greer Engineering and Indian parts. I plan to send him mine once I get the bottom plate smooth. I believe KIWI shows on his web site how he checks the oil pumps. He can also rebuild pumps if needed. I don't know if there are others out there that do that type of work.

[starklite]

As stated previously, the plunger in the cast iron oil pump is the culprit for causing wet sumping. The plunger to wall clearance gets too great and the oil goes straight into the bottom end of the engine.
Although what frustrates people is it does not happen every time. This is caused due to the where the plunger stops when you shut off the bike. If at the middle, you have leakage. If at the ends of the stroke, little to no wet sumping.

Whats the solution:
We take your oil pump, hard chrome the plunger, and hard chrome the oil pump.
Next we grind the the plunger and hone the oil pump so both have a perfect clearance better than new. Since the hard chrome is harder than the original pump material and it's running in oil, you have basically fixed the oil pump for the remainder of it's life time.

The above process is not inexpensive, but it's the best solution to solving the wet sumping issue.

Your rebuild process is quite extensive, after the above we will have the body cad plated, then reasemble the pump.
We then place the pump on our test stand and run it for 1hr and then after it's warm check the pressure the pump produces.
While these pressure numbers are arbitrary, our experience has found that when a pump holds these pressures they seem to work perfectly on the bike.

On a cast iron pump with a 5/8" plunger we want:
at 1200rpm -feed side: 60lbs minimum, and 1 cup volume in 54 seconds with a bleed down not more than 20lbs in 60sec
return side - 30lbs pressure minimum. Our new return gears usually produce 60lbs + on the return side

What's the cost:

CI-pump plunger hard chrome - hone, grind $235.00
Labor rebuild CI Oil Pump and test 3.5hrs - $75/hr
New return gears $50
41367 plunger cap $26
cad plate parts $50
42542 Plunger screw $11.50
misc gaskets/screws $6.50
The above gives you as good or better than new cast iron oil pump.

We usually have a couple rebuilt pumps on the shelf if you want an exchange vs waiting for the time to rebuild your pump. Or if you don't mind waiting, we can rebuild your pump. The biggest problem is CAD Plating - it takes 4-5 weeks on average to get the plating back.

If you have any questions on this our any other issues, please give me a call.

Sincerely,
Gary Stark
Starklite Cycle
951-968-3070
www.starklite.com