oil pump question

[pckopp]

78 Standard

My original outer oil pump rotor is cracked. The inner looks fine. There is a small amount of scoring on the inside of the surfaces where the rotors sit. You can see the scoring but you can't feel it, if that makes any sense.

I bought a new rotor and assembled it all and installed it in the cover. I put a tiny amount of lubricant on all the rotor parts and the housing. Seemed right. I can spin it by hand it moves freely.

If I tighten the 3 Phillips screws snugly, the rotor will not turn. Leave them loose and around it goes.

I measured the original rotors - inner is 8.00mm thick, the outer is 8.01mm. This on my budget digital micrometer. The new outer rotor is 8.09mm. Is this the problem? Or is there supposed to be a gasket between the oil pump housing and the side cover? I don't remember one, but it was awhile ago.

Educate me please. I can't seem to find an exploded diagram of these parts.

Thank you.

 

[Jim]

There is no gasket.....

Sounds like your rotor is too thick.

 

[azman857]

Looks like you need to sand down the outer rotor down some.

 

[TwoManyXS1Bs]

It's never easy, is it.
Have a look thru these:

http://www.xs650.com/threads/oil-pump.29486/#post-477691

http://www.xs650.com/threads/oil-pump-drive.49405/#post-507990

I compared the MikesXS stock 8mm pump rotor set to my OEM pump, and found a slight difference in the curvatures of the trochoid fingers and valleys. Just playing around with intermix fits, found that one intermix combo was too loose, and another just plain locked-up. I certainly don't recommend this intermixing.

 

[pckopp]

Okay. I have sanded the outer rotor to the same dimension as the original. I also gently knocked off the very sharp edges on the outer circumference. Felt like it would cut me it was so sharp.

If I put the two rotors together in the housing and put a straight edge across it, in bright sunlight I can see a tiny bit of daylight between the rotors and my straight edge.

I assembled it and it would not turn. Time to experiment. I put it together without the locating pins. Works fine. Put the inner pin in and it works. Put the other pin in by itself and the rotor turns but has some binding. Turns freely then binds up. I can force it by hand. Close inspection reveals the locating hole in the side cover for that pin has been buggered a bit. Edges of the hole opened a bit. The pin hole that works looks fine.

This bike has been down. You will remember the bottom of the engine repair I had to do on the low hanging nut. When I first got the bike the headlight bucket was mashed to one side, turn signals broken, handlebars tweaked. On the inside of the right cover there are stress marks. They don't go all the way through, but it isn't pristine inside. And the heads of the three Phillips screws have all been slightly damaged. Typical of using the wrong size tool. So I feel like I'm not the first one to visit.

My inclination is to put it together with the one locating pin that works and call it good. Appreciate your thoughts.

Also, should I lubricate the internals of the pump before installation?

From now on I will continue this project on its original thread here: There has been progress to report.

http://www.xs650.com/threads/refurbing-a-78-standard.47357/
http://www.xs650.com/threads/refurbing-a-78-standard.47357/
Thanks!

 

[TwoManyXS1Bs]

...My inclination is to put it together with the one locating pin that works and call it good. Appreciate your thoughts.

Also, should I lubricate the internals of the pump before installation?

I'd try to work over that 2nd hole until things line up. Then, hold twist/torque the cover in position while tightening the 3 screws.

You can pre-lube it if you like. But not necessary as it's below the oil line and will prime ok...