Bigtwin Oil Pump and swear words

Well the sumping issues I thought I fixed came back.
So I need pull the pump off and work over the check ball seat. This didn't go very smoothly, but I have to post it so someone else can learn.


Rear pipe has to come off.


Pinch off the gravity feed line.


Unpinch and dump the oil, because it needed to be changed.

Two hex bolts hold the inner housing and four socket heads hold the outer and inner housing to the crankcase.



Some bolts are in tight quarters.

Outer housing comes off.

This tiny circlip holds the drive gear to the shaft. It's tough to get off, and will give me more problems later on.

Clip's off and the housing will slide off now. There's a woodruff key with gear so don't loose it.

With a little a tap housing comes off.

Another drive gear and another woodruff key.

I pulled the cap, spring, and ball. Here's the seat and I don't really see any problems.

I should have gotten more pictures of all the red silicon in the oil passages. Don't use silicon in a motor. This might be what was hanging open the valve.

I had Rusty at Okie City Customs work over my valve seat. He had a special tool for cutting and I believe he lapped with a Evo pushrod, too.

So here we go back together. Cap, ball, and spring go in first.

You can't really screw up putting in the gears. The the wide ones go the crankcase side and the drive gears have the slot for the woodruff key.

Key goes on the shaft.

Gear on the shaft and key. It's a bit tricky to get the gear on there and not knock the key out of place.

Ooops! Put the gasket on first. The bolts are just holding the gasket while I put the key and gear back on the shaft.

Inner housing with idler gear goes into place.

Bottom bolts put in temporary to align everything for the outer gears to go on.

Key and gear go on and it's tighter and tricker than the last one.

Together! Fresh oil and everything.

This is where the swear words started. After the struggle to get it off, how could I forget to put it back in? I have a brand new on the bench, too.

Back apart and struggling to get the ring into the groove, because the shaft wants to slip in a bit.

More swear words! I let the outer housing attached to the hoses when put the ring in. The housing scratched up the ceramic coating on my front pipe.

Even more swear words! Look at that sump. Actually this leftover from before the pump rebuild and hoping my big sump problems are over.

Bigtwin Oil Pump Check Ball

Bigtwin Harley's will sump a bit a especially after sitting a bit, but this much is way too much. The check valve in the oil pump is a ball and spring, item 11 and 12 on this diagram. I read about this fix. It looked good, but I didn't want to take off the pump. If replacing the ball and spring doesn't fix it, I will try lapping the seat. Clamp off the gravity feed. Remove the inside cap. Here's the cap and spring out. You would think that a steel ball in an aluminum hosing would come out easily with a magnet on a stick, but that didn't work. The oil around the ball wouldn't let the ball out that easy. I has to use the mighty vac to get it out. It also helped to get any crud that may be in there hanging the valve open. The ball had a nice wear mark from the seat so hopefully the new ball and spring will fix the problem.