SOHC.co.uk Forums > CB350/400

Oil flow schematic

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Matt_Harrington:
Is there a diagram showing the flow of oil in the 400 like the one that is available for the 750? I don't seem to be able to find one.

The reason I ask is I'm trying to understand how so much metal got pumped around the original engine rather than the filter / strainer stopping most of it.
Does all oil go through the filter? Or does some bypass it?
It was highlighted by the fact that the oil restrictors for the head had half of the holes blocked on one of them with tiny metal fragments.....

Oddjob:
All the oil goes through the filter, unless the valve in the oil filter bolt is stuck, in which case it will bypass the filter. Maybe check the valve is moving?

I had the genuine oil flow schematic for the CB500, printed on a large cardboard plate. Nicked it from Queenies when they were throwing it out along with one of the full engine in an exploded diagram. Unfortunately the shed roof leaked on them and ruined them  :( :( :(

Isn't there one in the workshop manual? the 500 has one.

Matt_Harrington:

--- Quote from: Oddjob on August 16, 2023, 05:55:31 PM ---All the oil goes through the filter, unless the valve in the oil filter bolt is stuck, in which case it will bypass the filter. Maybe check the valve is moving?

I had the genuine oil flow schematic for the CB500, printed on a large cardboard plate. Nicked it from Queenies when they were throwing it out along with one of the full engine in an exploded diagram. Unfortunately the shed roof leaked on them and ruined them  :( :( :(

Isn't there one in the workshop manual? the 500 has one.

--- End quote ---

Mmm, just seen a flow chart - the implication is that if the relief valve operates, then the oil returns to the sump. (unless I'm mis-reading it)

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I have just taken the oil bolt out and the 'cup' the spring rests in has quite a deformed edge to it. so I'll replace that just in case.

Oddjob:
That's the oil pump relief valve Matt.

All the gearbox and primary shafts are lubricated by the oil splashing around. The 550 got a small little pump on the end of the countershaft, I don't recall the 400 getting that

Just a thought but maybe the filter blocked at some time in it's life, the valve opened allowing all that swarf to pass around the engine before the filter was changed again

Matt_Harrington:
Yes, that is a possibility. I threw out the old filter by mistake otherwise I could have inspected that.

The whole bolt assembly isn't that expensive, so may just replace completely.

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