SOHC.co.uk Forums > CB750
top end oil feed problem
UK Pete:
yep it has to be oil jets, a very common problem, the engine has to be spotless when rebuilding, and always check the jets are in and clear, also worth turning the engine over by starter or hand before running to see that oil is making it up the top, any future engines that i build will be bench run to save any hassles which require engine out
pete
Bryanj:
As stated the smallest particle of gasket debris will block those jets as will any silicone gasket that gets there
K2-K6:
You wouldn't see this loss of flow with the oil pressure light in any normal event.
The jets as far as I know are there to maintain the oil pressure to the crank bearings which is measured by the oil pressure switch. Past those oil restrictions is essentially a low pressure area that leaks out slowly from the cam bearings and leaves a pool of oil for the cam lobes to dip into.
The blockage of one or both jets is likely to have come from one of the gasket faces during assembly as it would not usually pass through first the oil pickup screen then the oil pump rotors and then via oil filter to get to the jets. so you are really looking at maybe joint face of crankcase or base gasket of barrels or the head gasket as the primary suspect.
mike the bike:
I always crank the motor over on the starter to check if the oil is reaching the camshaft. I feel your pain though.
adriangsmith:
Hi All,
Thanks for the replies and advice,
That jet was definitely blocked with some gasket debris. now kicking myself for not ensuring all was clean.
Took all top end apart and now decided on a full rebuild of the engine as detected some play in the main bearings.
More work and new territory for me as never done any bottom end work on an engine before!
Still looking for a replacement cam tower and camshaft ready for the rebuild if anyone has one lying around in a box of spares!
Heres hoping for better luck this time round.
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