Topic: Proper large oil pump o-ring 46 x 3mm CB650 CB500 CB550

[grasscutter]

School me, oh you o-ring guru's!

After a few searches, I came up with some info on finding the correct large oil pump o-ring.  The one that fits behind the 3 screw front plate. 

Per OEM Honda:  1981 CB650:  91309-703-000    O-RING (46X3) (NOT AVAILABLE)
Per OEM Honda:  1978 GL1000:     91305-426-003    O-RING (46X2) 
Approximately $5 for the GL1000 o-ring, and its available.

McMaster Carr also has the BUNA square o-rings specifically for oil applications up to 212deg F.  But, unable to find them in the correct mm size.

Most posts I've searched through have the size listed incorrectly.  Everyone seems to be talking about a 46 x 2mm o-ring, when its supposed to be a 46 x 3mm.

So, here's my questions:
1- The closest Honda has now is 46 x 2mm.  Would this cause oil pump leaks? 
(2mm = .078"  3mm = .118".  Difference of .04".  Not much difference, yet being off .04" when setting the valves will cause problems.  Follow my reasoning?)

2- If I find this o-ring locally, how do I find one that is compatible with high temps, and oil?  Assuming Viton, since its rated quite a bit higher.
(Nitrile up to 225deg F and Viton usually to 390deg F)

3- Has anyone else found a source for the correct o-ring?

[grasscutter]

Found!

After many wasted hours looking locally and online...nothing.

Found them @ a Honda dealership in Denmark.  They had 5.  Bought all 5.  Shipping less than $10 air mail.  Will have them in a week.

Had my local Honda dealer do a nationwide search, and he found nothing in the USA.
He had a 46 x 2mm, which everyone says is correct.  Not true.
Its close enough to get you by.  And may work for awhile.  But for the CB650 oil pump cover, it is not correct.  Correct Part # 91309-703-000.  46 x 3mm. 

So, guess I've got the last 5 (unless others turn up somewhere). 

[bryanj]

It might possibly be 3mm for the 650(never stripped one but i doubt it) but its 2mm for the 500/550 mate. Plus the number you quote for the  650 is for the oil pump to crankcase NOT the top cover.

Tried a 3mm and the cover doesn't go down far enough so oil pressure drops a helluvalot

[trueblue]

I just took mine into the local bearing supplies and got them from there, matched size for size.  Cost me $2 for all the o-rings .