Author Topic: CB550 oil leak from sump bolt/washer  (Read 1599 times)

Offline Harold 400/4

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CB550 oil leak from sump bolt/washer
« on: September 08, 2025, 02:04:46 PM »
Looking for advice pls.
I’ve got an annoying oil leak from my sump bolt. It’s only a minor leak but I need to sort. The sump threads look fine and the bolt torques up OK. I have tried a new crush washer, but to no avail. There is no sign of any cracking to the sump.

What I have noticed is the surface on the sump where the washer sits is scored, and the old washer I took off is also scored. I am thinking this may have happened as a result of the sump not being properly cleaned of muck when previous oil changes were done??

Is this scoring enough to cause the slight leak I am experiencing? If so, what’s the best way to sort??
Cheers
Harold

Offline Johnny4428

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Re: CB550 oil leak from sump bolt/washer
« Reply #1 on: September 08, 2025, 02:58:03 PM »
This is maybe stating the obvious but make sure the washer or bolt is not riding up against the raised edge of the bolt flange. Also make sure there is not another old crush washer still on the drain bolt.
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1961 Matchless G3
1974 Honda CB550K1
1978 Honda CB550K3
1999 ST1100 Pan European 50th Anniversary.
1975,1984,1986 Honda C90’s
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1977 Honda CB550 (almost)

Offline McCabe-Thiele (Ted)

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Re: CB550 oil leak from sump bolt/washer
« Reply #2 on: September 08, 2025, 03:48:43 PM »
I think the washer should be made of Aluminium, a use once type.
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Online Bryanj

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Re: CB550 oil leak from sump bolt/washer
« Reply #3 on: September 08, 2025, 04:21:07 PM »
It is supposed to be a single use ally washer but copper should do, maybe trya dowty hydraulic sealing washer