Topic: 750f oil pump

[jlazyh]

I have a 1973 CB 750. Would someone fill me in on how to get to the oil pump, and the best way to clean it? Heck I don't even know where it is.

[MRieck]

You have to drop the oil pan. You will have to remove the exhaust system to access it. There are about 12 bolts to come out and you are there. Cleaning the screen is about the only thing that can done woithout pulling the pump out and disassembling. I'd buy new exhaust gaskets and an oil pan gasket prior to disassembly. Thank you for your years of military service...it does not go unappreciated.

[Jonesy]

If the bike in question is the one pictured in your avatar, you'll have to remove your exhaust system.

On the bottom of the engine there is an oil pan cover. Drain the oil and remove the bolts holding it on, keeping track of which bolts went where, as they are different lengths. You can push them into a piece of cardboard to keep them in place. One of the bolts is very close to the pan, so you'll need a thin-walled 10MM socket to get it off. If you carefully drop the pan, you should be able to preserve the gasket.

Once the pan is off, you'll see a large, round oil pickup with a screen over it. This is the pickup on the bottom of the pump. There are 3 bolts holding the pump on, and there are hollow dowel pins next to the bolts with O-rings around them. The O-rings will likely be flattened out, so it might be a good idea to replace them when you put it back together.

[Sam Green Racing]

Are you psychic as well as magic Mike

[jlazyh]

Thankyou all. This helps so much.

[Clyde]

It is worth checking parts 10 and 11 from the above diagram. These are the non return valves that stop wet-sumping.
With these old bikes there is a chance the plunger will be sticking (usually just varnished up) or there may be some crap/gasket under the plunger.
There are three bolts holding the oil pump in the crankcase. Once the oil pump is out there are two bolts holding the non return valve together.
When you have it all back together it is sometimes hard to prime the oil pump. My suggestion is to is to pour as much oil as you can into the oil gallery behind the cylinder block. This done by removing the little cap above and to the left of the points cover. You will need to lean the bike over to the left to get enough in.
I also pour about 50cc of oil over each valve by removing the valve cover. This means you have some oil in the top to start with and also means you have some oil in the sump to prime the scavenge pump.
Good Luck
Clyde

[jlazyh]

The reason I think I need to clean the pump is, I have changed the oil and filter. However even on a warm day it takes several miles of easy driving to get the oil up to quiet down the motor. Its just like throwing on a switch when it starts oiling. From alot if motor noise to dead silent and smooth.

[Jim Shea]

Difficult question, but what sort of noise is it?

[jlazyh]

Difficult question, but what sort of noise is it?

It's the lifter noise just like you get in your car when you are low on oil. When the oil gets up there it quiets wright down and is fine.

[JonnyHonda]

Lifter noise in a car, is normally due to low/thin oil because the tappets are hydraulic, noises in bikes like these that "Go away" is normally due to warming up and the engine coming into tolerence.

I always half recommended oil related changes, you can never go wrong then. I had one bike "gsx250" that always had "tappy" tappets, turned out that the PO had not paid attention to clearences and a pit had worn into the back of the valve. When I asked the guy if he ever checked the valves, he said "Yes, I was always having to tighten 'em down the kept comming loose"