850 commando oil pump issue

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Hello all, Newbie here. My 850 had a sudden drop in oil pressure again. This is the second time over many thousands of miles that the pressure dropped in the same way. Was 60 cold, 40 at 3K rpm, 20 at idle now after last ride 40 cold, 10-20 at rpm 0 at idle. Frothy oil returning to hold a good level, does not drain the tank just off the dipstick overnight. I have lapped the pump at least 3 times. It has been 2000 miles since the last time this happened All seals etc were replaced but no sign of gasket/seal failure that would cause this. The pump was as snug as I dared lap it. I have heard about O rings for the pump but could not find any details.
I just changed the oil and filter and inspected the other strainers and plug and no improvement Any help will be appreciated
 

L.A.B.

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Have you checked if the pressure relief could be sticking?
If in doubt, replace it.
The O-ring seal mods would be unlikely to affect the running oil pressure I would have thought?
I take it you have checked/replaced the crankshaft oil seal?
 
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850 oil pump issue

what type and weight of oil are you using?, a thin synthetic may have tendency to froth in a loose pump,when I lap an oil pump I have it so that it will NOT turn by finger pressure,I put a wrench on the nut and use LIGHT pressure to turn the pump.How reliable is the gauge that you are using?, oil pressure gauges on our older bikes worry me,as long as you get a good return flow to the tank forget the pressure gauge -- that statement will promote argument I'm sure!!. Recheck your pump,tighten it up as described, Good luck.Ride safely. James.
 
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oil pump lapping

I only lapped the pump until slight resistance to turning was felt so perhaps it was nowhere near tight enough. I will check all seals etc and perhaps renew the relief although I only cleaned and inspected it last time and the pressure did return for a few k miles with golden spectro oil I think Thanks
 
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I do as James, lap till just can't turn by had but can using spanner with light pressure, but more likely your pressure release is at fault or your feed pipe is failing internally and closing up under sucton or a piece of rubber is coming away from the inside and blocking the flowto the pump.
 
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