Topic: Oil pump rebuild.

[maxheadflow]

In the process of rebuilding the oil pump on my CB750K8.  I found a rebuild kit plus I also found out that cometic sells an AFM gasket kit. I understand that the paper gasket under the pump can blow out. The Cometic kit has an afm gasket in it for the pump.
The pump rebuild kit has the inner pump, the oil check valve rubber, and new springs. IIRC I got the kit from 2fastmoto off of ebay..

I plan on using the cometic pan and oil pump gasket and the kit to rebuild the pump.  Will likely tighten up gerotor end play. Any other suggestions?

https://www.ebay.com/itm/203804047624

[brianc]

Pay close attention to the thin base gasket. If too thick (sorry not sure of original spec) the drive gears will bind! A thick gasket lifts the pump too close to the kick start gear which drives it.

[maxheadflow]

Have you seen that happen?   It was one thing I'm curious about..

[brianc]

Yep -to me!! I can't remember the brand of gasket kit, it was a few years back. The original is pretty thin, this one was probably 2 to 3 x that.
Pretty sure the Vesrah kits are OK. I'll find out soon, I'm building a 750 back up in the next couple of weeks.

[maxheadflow]

Thanks for the reply.

I was going to check the gear lash.. The gasket in the pump kit is 0.020 which the cometic is 0.030.. I think I have a Vesrah pump gasket around here someplace.. I could take 0.010 off the bottom of the oil pump..

[maxheadflow]

Brian, Thanks for the info. I measured the gaskets and the Comtic was about 0.030", the one in the kit was 0.020" and the Versys was about 0.006".

I got lazy and used the Versys..

The pump had been rebuilt some time before has the end covers O rings looked to be SAE and not metic. 

The oil seal in the middle of the pump was hard and I could break the rubber apart with a fingernail.

I used a lathe to bore the seal out until the body cam loose..

[maxheadflow]

The O ring both old and new looked to be the same.. The one that came out was squarshed flat and only 0.060" tall.  I expect it was a SAE O ring and not metric..  The O ring clearance measured out to be about 0.055".  The new O ring measured 0.077 which kinda told me that it was 1/16" and not metric.   

With that being the case, I tried to measure side play on the rotors as I was thinking the load from the O ring could bow the cover. Didn't really see anything. It measured at about 0.002" side play without the O ring. I figured that I'd set the pump up for more of the proper compression on the O ring.

I fixtured the pump, and cut about 0.012" off the O ring seat. I checked to a new O ring and a feeler gauge. Preload on the O'Ring was 0.012"

[maxheadflow]

The big issue was the tank oil draining into the motor.  I've got a 100 miles on it so far and the pressure seems a little better.  Fresh oil can do that tho.  The good thing is that the oil seems to be staying in the tank now.