Topic: CB 750 K2 oil pump..what is this?

[Hastenbrucke]

Does anybody have an idea of what this strange modification might be on this oil pump. Ace is holding it...we are not sure?
I

[lucky]

Sanding to remove chisel marks.

[Hastenbrucke]

Thanks Lucky.  Is that normal. From factory or has someone done something nasty?

[Hastenbrucke]

I guess what I am asking is do you think the pump has been damaged, plugged and pinned?
It surely can't be like that at manufacture?
Any thoughts?

[Jerry Rxman Griffin aka MuthaF'er]

That's not a stock thing. That much I do know.

[ekpent]

Some pictures I saw on E-bay show various casting marks there. First pic I think is a K0 and the other is a later maybe Kor F.

[Ace]

Some pictures I saw on E-bay show various casting marks there. First pic I think is a K0 and the other is a later maybe Kor F.

I'm tending to agree.  There is another plug mark on the back so I reckon to drill out the tunnels they straight line bored it and then plugged it.  Later on they changed how they cast the oil pan.  I got another base from my stash and cleaned them up. A very different finish on the plugged one, different method of casting, sand casting....just throwing it out there.  In your pics ekpent you can see the different cast finishes.

[754]

This is from the motor that had the rod damage?
 Looks a bit like they had motor apart and changed a lot of stuff rather quickly . If a rod had blown and there was a lot of debris, a lot of guys would change the pump , if they had access to one..

[Ace]

This is from the motor that had the rod damage?
 Looks a bit like they had motor apart and changed a lot of stuff rather quickly . If a rod had blown and there was a lot of debris, a lot of guys would change the pump , if they had access to one..

Yep same motor with the rod damage. Someone has opened the engine up and replaced parts, so maybe the oil pump as well.

Took the rods of the crank and someone has put new bearings in there.  I was curious so I decided to plasti gauge the crank and rods. Most were at 0.025 for a used set of bearings. The underneath side of the shells looked as though heat got to them as well. Not sure if it's from tight bearings or they reused some of the old ones, but strange that used bearings yield 0.025 clearance on plasti gauge.

[Hastenbrucke]

Hey 754. Yep it is. We are starting to build a story here. From my post regarding a oil pan debris,to oil pump mystery, it's obvious to me that there has been a major issue at sometime and whoever did the re build did a quick and perhaps not as good a job as they should have, who knows.
A least now we do know and it won't  go back together without it being as it should be.
Might take time and therefore $s however it will be right.
I guess I have to find an oil pump??? The search begins.

[754]

The oil pump might be ok, it probably was put in after the old one ingested all the crap from the rod bearing... Not sure why you are tearing down, but pump is not always bad.

[Ace]

The oil pump might be ok, it probably was put in after the old one ingested all the crap from the rod bearing... Not sure why you are tearing down, but pump is not always bad.

I take if you are meaning a full tear down not just the oil pump? Piece of mind knowing that the engine is good after finding remains of metal in sump. Fixing issues as we're going along to make sure this near bullet proof engine will be once again after the rebuild so all you have to do is ride it!

[Hastenbrucke]

Indeed ACE????that is the plan.

[Ace]

Here are the pics of the different oil pumps.  The plugs IMO are meant to be there due to casting differences.