Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Neill C on August 19, 2023, 06:23:43 PM
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Hi all. I've 1500 miles since having an engine rebuild and have a small amount of oil coming out of the crankcase breather. I think this only happens after I've ridden it at higger speeds than normal. Is this something to worry about?
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Check the oil level correctly to start with. It should be just fumes coming out of the breather but raised crank case pressure could cause oil to come out.
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Hi all. I've 1500 miles since having an engine rebuild and have a small amount of oil coming out of the crankcase breather. I think this only happens after I've ridden it at higger speeds than normal. Is this something to worry about?
No, normal.
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Thanks guys. I'll check the oil level in the morning.
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If you keep the oil level somewhat lower than MAX, you will see less oil coming out of the breather tube.
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Hi all. I've 1500 miles since having an engine rebuild and have a small amount of oil coming out of the crankcase breather. I think this only happens after I've ridden it at higger speeds than normal. Is this something to worry about?
The rebuilt engine requires a full service after 500 miles run in period and you would of noticed if it was low then.
You should not have any oil coming from the breather unless the engine is old and high milage. Was the piston to bore clearance correct at the time of rebuild ?
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I think we have to distinguish between oil pouring and tiny oil spats. The latter I have always had after hot rides for 43 years.
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The rebuild was carried out by a classic Honda specialist and had a rebore with larger pistons so I assume they are OK. The oil isn't pouring out. Just enough to wet the end of my finger
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A little oil can depend on a lot of things, including the grade of oil in the engine. If you have drips on the deck, i would suspect that it was not rebored to the correct spec .
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Assuming that is correct and I can't go back to the garage that did it as it was 3 years ago now and seeing as I only use it for coffee and chip shop runs should I just live with it?
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Assuming that is correct and I can't go back to the garage that did it as it was 3 years ago now and seeing as I only use it for coffee and chip shop runs should I just live with it?
I wouldn't loose any sleep over it if you hardly ever use it. But, it may have an issue that will get worse.
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Thanks. I did check the oil and its up to the top on the dip stick(when unscrewed) and would could even go slightly over. It depends on how level I think the bike is when checking it. How do you get it perfectly level in the first place?
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Its normaly checked on the centre stand with dipstick just resting on threads, the difference in angle for the bike to be able to sit on centre stand on slope should make little difference , in theory but we all know about theories!
Most import thing is to check it same way every time so you can see if you are using any
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Thanks. I did check the oil and its up to the top on the dip stick(when unscrewed) and would could even go slightly over. It depends on how level I think the bike is when checking it. How do you get it perfectly level in the first place?
Something about that statement worried me, I presume you mean up to the top of the markings on the stick not to the top of the stick itself. Also check cold not hot.
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Yes. Up to the markings and stone cold.
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Do a compression test, just to be safe. All the plugs out and the throttle wide open.
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CB550s which had the breather tube connected to the air intake - to comply with US law - often had the paper air filter element fouled. A remedy much practised was to have the oil level not higher than halfway the two marks on the dipstick. But as has been said earlier: I wouldn't loose any sleep over it.
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As is often the case my experience is more with cars than bikes fwiw I had an old Merc 300TE 4-matic that when I was driving it at speed would start to throw a massive cloud of black smoke out of the engine at high rpm. First time it happened I thought I had blown the engine on my way to Skegness as my speed dropped it stopped smoking & drove normally.
When I pulled into a lay-by I checked the oil level it was difficult to check due to what I would describe as oil foam on the dipstick - it appeared to be slightly overfull. The dipstick that had a rubber grommet where it entered the block had also been pushed partway out of it's seat.
It appeared to be that the combination of high engine revs using a modern synthetic oil had caused excessive oil mist to get past the rings. I ran the car for a further 4 years without any excessive oil consumption or issues unless I pushed it close to its rev limits.
Thinking about the sort of revs these Hondas reach it strikes me that oil misting might account for some of the fumes from the top vent - I would not be too concerned unless it started smoking excessively as well.
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Thanks all.