Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Dolomite_ on March 29, 2026, 12:14:42 PM
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What I thought might be a leak from the oil pan turned out to be from the oil pump. I've not had a chance to start it up with the chain/sidecover off to see where the leak is coming from but I suspect its from the oil pressure switch. When I stripped it I used Julie's O-ring kit and replaced them all.
Whats the best way to way to help prevent oil seeping up the thread of the oil pressure switch? Would PTFE tape be fine?
If its not the oil pressure switch what would be best to add some more seal protection to the surfaces of the oil pump?
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Did you clean the oil relief valve & check it operation?
Unless it's a new switch it might be leaking at the terminal & oil seeping down, never needed PTFE tape on the threads.
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More common is the gearchange shaft seal under the same cover, you can use ptfe tape but it is a tapered thread and should not need it BE CAREFULL as it is tapered doing it too tight can crack the housing of oil pump
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I rebuilt the engine just under 2 years ago so all the seals are pretty much new.
Ted
Is the oil relief valve in the oil pressure switch?
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Wouldnt be the first new seal i had leak!
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I rebuilt the engine just under 2 years ago so all the seals are pretty much new.
Ted
Is the oil relief valve in the oil pressure switch?
Iirc it's built into side of the oil pump, I could be confused with the 500 oil pump.
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The pressure relief valve is in the pump as Ted says.
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I cleaned the oil from the pump, checked the bolt toque and seals. It all appears fine.
I went out for a ride today and checked when I got back, it's coming from the oil pressure switch. I'm going to check the oil pressure switch is torqued correctly later this week.
Are there any other measures I can take? Or is it a case of replacing the switch and testing it?
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Torque on that part wont work as it is a tapered thread, new switch with a small amout of liquid ptfe or tape and not super tight or you can crack the casing