Author Topic: mysterious oil leak  (Read 316 times)

Offline mickwinf

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mysterious oil leak
« on: August 07, 2025, 04:03:55 PM »
I have been chasing oil leaks on Lazarus the 500 four, not the usual top end ones but from undrneath. Ended up replacing the sump and then had to get a genuine seal as the pattern one still seemed to leak, then realised the clutch cover was also leaking so maybe sump was ok after all. I did use sealant this time and after a test ride it looks like success. However i noticed some oily stuff on the top of the crankcase and around the starter motor cover. Double checked the head and rocker cover joints and tappet caps and all looked dry. Then I thought it may be from the breather as I dont have a pipe on it at the moment but would expect that to send iot all over but no sign anywhere else. I checked my fuel tap and it was damp and the pipes seem a bit sticky. I used the silicone pipe that is supposed to be ethnol safe but could it be that?
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline Athame57

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Re: mysterious oil leak
« Reply #1 on: August 07, 2025, 05:18:49 PM »
When I had something a bit like this on my CB400F it turned out that the oil pump needed new 0 rings.
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Offline Bryanj

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Re: mysterious oil leak
« Reply #2 on: August 07, 2025, 05:44:09 PM »
Is this when standing?

If the outside of the pipe is stickey where all along it suggests failure also if soft on the spigots.
Reason i ask about standing is years back i had lots of fuel dripping when the fibre washers under the tap holding screw heads cracked, i found generic 6mm fibers were too thin and cracked when tightening then fuel came down the sxrew threads continuosly filling the carbs and pipes

Offline Johnny4428

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Re: mysterious oil leak
« Reply #3 on: August 07, 2025, 08:55:57 PM »
On the subject of oil leaks, it would appear that some aftermarket sump gaskets are too thin. I just used the one from the gasket set but ended up buying the correct OEM one and all was fine. Think it was a Vesrah set.
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Offline mickwinf

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Re: mysterious oil leak
« Reply #4 on: August 07, 2025, 11:37:56 PM »
Bryan I have that problem too, I rebuilt the tap but still drips when tap turned off.think I used douty washers.
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline deltarider

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Re: mysterious oil leak
« Reply #5 on: August 08, 2025, 08:04:45 AM »
Does the oil on the dipstick smell of petrol?

Offline Bryanj

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Re: mysterious oil leak
« Reply #6 on: August 08, 2025, 12:22:02 PM »
Dowty washers only work about 60% of the time, it depends on the quality of the tap casting, i am sure that original dowty washers were ally with rubber insert but they now seem to be steel with rubber insert.
The honda part is damed expensive for what it is but does work
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Offline mickwinf

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Re: mysterious oil leak
« Reply #7 on: August 08, 2025, 05:38:16 PM »
Hi Bryan, I did order some original sealing washers but they seemed to be different to the originals I have had before as a lot thinner. And they leaked
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline Bryanj

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Re: mysterious oil leak
« Reply #8 on: August 08, 2025, 05:53:37 PM »
Wonder if the dealer you got them from just sent crap? I would be tempted to wind some gas fitters ptfe tape arround the screw thread, yes there is a different tape for gas and water

Offline mickwinf

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Re: mysterious oil leak
« Reply #9 on: August 08, 2025, 10:21:25 PM »
Got them from silvers
Love the 500 and 550 have a 500 called Lazarus under restoration

Offline Bryanj

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Re: mysterious oil leak
« Reply #10 on: August 08, 2025, 10:58:02 PM »
I would complain to him

Offline McCabe-Thiele (Ted)

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Re: mysterious oil leak
« Reply #11 on: August 09, 2025, 06:37:57 AM »
Wonder if the dealer you got them from just sent crap? I would be tempted to wind some gas fitters ptfe tape arround the screw thread, yes there is a different tape for gas and water

Water is usually white PTFE tape.

Gas is usually yellow PTFE tape.
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This is a neat 500 restoration in the USA.
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Offline JezzaPeach

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Re: mysterious oil leak
« Reply #12 on: August 09, 2025, 01:33:58 PM »
My 500/4 had the cam top breather pipe missing and I think an oil mist had circulated around causing filth to stick in lots of places. Also a drop of oil hanging off the sump fins but not really dripping turned out to be oil pump seals, but only while running, losing a lot of oil. Seals from Julie.
My fuel tap was letting by, not good. Seals from DSS and I used a little PTFE cycle grease just because it’s what I had to hand and it’s lasted well.
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