Topic: CB550 oil leak front from front cover of oil pump.

[Brocky]

I'm doing a full rebuild of my CB550 and made the mistake of taking off the front cover of my oil pump.  It now leaks. This cover has three countersunk JIS screws (not Philips, a Philips head will round off your JIS cross head screws). Honda diagrams (go to cmsnl.com for excellent diagrams) do not show the O ring seal for this cover on the 550. However, it is the same O ring diameter and thickness for on an old Goldwing water pump, part number 913 0542 6003 which is a 46mm (inside diameter) x 2mm (thickness of nitrile ring) O ring.
I will cost you just below £5 (2022) delivered from David Silver Spares or you could try to get a 46 x 2 nitrile O ring off Ebay for about £1.75 (Nitrile 46mm ID x 2mm C/S O Ring. Choose Quantity. 46x2 mm. New. Metric.).
I have seen some posts that say it's a flattened O ring but I think that's just because its been squashed in situ over time. I could be wrong here and all the following and previous O rings are circular in section.

Having said all this I still haven't quite solved the issue (I still have a very small leak) having tried both of the above so I'm going to try an O ring of the same ID but thicker cross section (46 x 2.5mm) to see if that works. Simply Bearings do one, coming in at about £4 for the pair. I also notice that there are grades of Nitrile, 70 shore and 90 shore being the most common, the 90 being a harder compound. I'm not sure (no pun intended) which is best for my oil pump cover so am going to try the softer 70 to start with and go to the 90 if that doesn't work. I also notice that some nitriles are only recommended up to 135C and the engine oil could get hotter than this (about 150C I think) so I can't necessarily recommend my course of action without checking the nitrile specification of your chosen purchase.  I note that Simply Bearings nitrile is only recommended up to 120C. You do not want any degraded pieces of rubber in your oil pump. I'll let you know how I get on.

[newday777]

Welcome aboard Brocky
As to a flattened O-ring, Honda did offer some that had a flat surface on the inner diameter so they were technically a D-ring as opposed to a O-ring. One was on the GL1100 final drive to seal at the swing arm connection, but it was too large diameter for your cover, I dealt with that on my 1983 GL1100 that I restored in 2009 and they were discontinued from Honda at that point.......
 
I haven't had a 550 since the 70s and never took the cap off the oil pump so I cannot confirm if it was a D-ring or an O-ring. 
I don't remember seeing any D-rings in the parts room when I was parts manager in 1976 and 1977, but I know my way around looking up parts still. BTW, when talking parts and bikes be sure to mention the year/model and K series your bike is or as in your reference to the Goldwing, there are many changes in parts from year to year and model changes, IE,  GL1000 to GL1100 and so on.
Hopefully someone will be able to help clear up your situation on your leak.

Go to the new members section and introduce yourself and your bike.

[bryanj]

It is 46x2 and a thicker one wont compress enough leaving the cover too far away from the rotors which will drop oil pressure considerably.
It was me years ago that sorted out the size and i spent some considerable time in a big hydraulic suppliers sorting out the size, if it leaks after a new O ring either its twisted, the cap is cracked or its leaking down from the pressure switch on top

[Brocky]

Thank you for both your replies Newday777 and BryanJ. It's so good having this support out there. I will go to introduce myself on the new members section but I could say here that I have a CB550K3 from 1978. Good point re rotor clearance I hadn't really thought that through. I had a look at my old O ring that I took out and measured it again. It is a rectangular section with an inside diameter of 46mm an outside diameter of 48.3mm (2.3mm thick radially) and 1.4mm thick axially. I'm not sure of these are original measurements or worn down as a result of 45,000 miles service. I measured the Gold wing part (can't remember the year now) and it is 46mm x 1.8mm (stated at 2mm) circular section O ring. Yes I was about to say that it wasn't leaking before so I don't think its a cover issue but to be honest the engine was in such a mess I'm not sure if I would have noticed. I'll inspect the cover again to look for any cracks or defects. Thanks again both for your input.

[bryanj]

It could be the wing part is speced at nominally 2mm, i bought 46x2 from the hydraulic supplier, unfortunately dont want to go back as they now have a £100 minimum order which is why i no longer do oil pump kits BUT Nurse Julie on here has a kinder wholesaler and does oil pump kits although you will have postage from UK, i would say get the carb O ring kit but you have the god awful PD carbs on yours and i dont think she does those.

[Nurse Julie]

As you're in UK, it would be better joining the UK Forum on www.sohc.co.uk as we're a lot more local to you 😊😊😊
As Bryanj said, I sell the oil pump O ring kits here in UK. £10 to forum members and post at cost, so £11.05 all in.

[Brocky]

Hello Nurse Julie,
Ok that would be great thank you. How do I go about buying one of those from you?

[Nurse Julie]

Hello Nurse Julie,
Ok that would be great thank you. How do I go about buying one of those from you?

I'll send you a PM via this site for now.