Oil Pump Rebuild

mcconnellfrance · Post by **mcconnellfrance** » Tue Jun 16, 2015 3:20 pm

I am rebuilding the oil pump for my 1965 CB77 engine. I have bought some new gears from CMSL to the part numbers in the CB77 parts manual (15131-250-00 and 15141-250-000).
On installing these in the pump, I found that the pump was seized when I tightened the 5 five screwsdown on the side casing. The standard single paper gasket was installed.
It seems that the width of these replacement gears is 5.5mm. The old gears measure approximately 4.5mm. Reinstalling the old gears cures the problem.

I am wondering if the gear width and pump housing changed at one point in time? (perhaps from the CA72/77 to the CB72/77?).

Grateful for any knowledge on the subject.

Gordon

G-Man · Post by **G-Man** » Tue Jun 16, 2015 3:30 pm

Gordon

Not sure what those gears are from as I believe the gears never changed. All 4.5mm.

May be from another Honda. One of the early dry-sump dreams had two sets of gears. The scavenge gears would have been bigger, so they might be for a C70/71 twin.

http://www.cmsnl.com/honda-c70-c71-cs71 ... ml#results

G

mcconnellfrance · Post by **mcconnellfrance** » Wed Jun 17, 2015 4:12 pm

Graham,

Thanks for the reply. It certainly seems that the new oil pump gears are from an early Honda pump as they are dimensionally identical to the gears in my pump except for the 1mm extra thickness. I will investigate a bit further and post a picture or two tomorrow. I will have to use the old gears but they are not so badly worn. My fear was that I had found another 'error' of fitting the wrong pump in the previous rebuild i NZ.

Incidentally, got my zinc plated parts back from Derby Plating. They have done a great job, looking just like new parts.

Best regards,

Gordon

G-Man · Post by **G-Man** » Thu Jun 18, 2015 12:44 am

Gordon

Another pitfall I hadn't thought about when ordering parts for these old bikes.

I have actually worked out a design for resurrecting worn out pumps with slightly larger gears bought from HPC gears in Chesterfield. The gears come as a long blank and have to be divided into two.

For the pump I did, I chose 6mm width and machined the pump casing and gears accordingly. The HPC gears are 1mm larger diameter too, allowing cleaning up of all the scores in the pump body.

Great news on Derby Plating.

G

mcconnellfrance · Post by **mcconnellfrance** » Fri Jun 19, 2015 5:06 pm

Graham,

Excellent work on design and machining. I wish I had some of your skills.

The oil pump has some scores inside, I hope not too deep to reduce the performance by much. I have attached some photos.

The gears thickness was 4.38mm on the existing gears and 5.38mm on the new ones I bought from CMSL. I agree that the only possibility is that they are from an early four gear pump. Perhaps CMSL has put them in inventory under the wrong part number. I will get back to them.

I have had no choice but to reassemble the pump with the old gears.

Also, some bits back from Derby plating - very nice.

Gordon

Difference in gear widths between existing gears and new ones by

[url=https://flic.kr/p/uBezQq]

Scores on oil pump cover by

[url=https://flic.kr/p/uTkTgS]

Scores on oil pump body by

[url=https://flic.kr/p/uBuq89]

Zinc Plated Parts by [url=https://www.flickr.com/photos/131927779@N07/]

mcconnellfrance · Post by **mcconnellfrance** » Fri Jun 26, 2015 12:40 pm

Had some quick answers from Christiaan at CMSL:

"Dear Mr McConnell,

I went into our warehouse to check our stock aswell. I did find multiple 5.4 gears and a few 4.4 - 4.5mm thick gears aswell. I removed the 5.4 gears from stock.

To speed up the process I already made a service order for you. The right gear will be shipped out later today.

For me, I would still like to receive your data so I can pinpoint the small gear to your model (Via your vin I'm able to pinpoint exactly your model), and I'm maybe be able to pinpoint the thicker gear to an other number and can help our customers to a gear that has been discontinued and out of stock for ages.

If the gear you've got needs to be shipped back or be binned depends on the value of the gear. Thats is also one of the reasons I would like to find out what the partnumber is of the gear you now got."

and after giving the VIN number to him:

"Both gears you received appears to be 259 gears (15131-259-000 and 15141-259-000), so for us it is worth it to get them back. I created a RMA form for you, emailed it to you and I would like to ask you to ship them back to us. Can you please add the form to the return envelope?

You bought our last 15141-250-000, so at this moment I'm unable to supply you this. But there might be a possibility I'm able to find one. Next Monday or Tuesday I will have time to look in a shipment in where I might have seen this part.
So I would like to wait for that before we decide to refund you the 15141-250-000 or to replace it (maybe we are lucky and I can send you a replacement)."

So now hoping that Christain can find another 4.5mm Gear B at the beginning of next week. Very good support from CMSL.