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Discussion Starter #1
I dropped a spare engine in my bike after a drastic failure....any idea why with everything put back together I am having a low oil pressure problem. With a cold engine the light comes on below 2k RPM. as the engine heats up the low pressure light only stays off with more RPMs....is this anoil pump problem or simply moisture and air in the crankcase ? I have run 16 quarts of oil through the engine. When I start the engine the oil in the window becmes cloudy. plus the bike holds 3.1 liters according to the specs... hwever it shows overfull after adding 2 quarts. any idea?
 

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Could be:
A) Defective oil pressure sensor. Temporarily replace with an actual gauge to see what you're actually getting for pressure.

B) Defective/plugged oil filter. IIRC, they have a bypass in 'em so they won't clip your oil pressure, but it may be bad.

C) Oil pressure relief valve in the oil pump may be stuck open. Or it's spring may be broken or weak.

D) Strainer screen may be gummed up or plugged up with debris. This is a common problem with 'spare' engines. I have FHE.

What's the history of this replacement engine? Did it have good pressure in the past?

A general rule of thumb is at least 10 psi for every 1000 rpm. That's kind of a car hotrodder number, but it's not bad.

My S4 Service Manual says:

Cold engine, oil pressure should be over 37 psi at 1100-1300 RPM, and between 59 - 88 psi at 3500-4000 RPM.
With the engine hot, pressure should be over 16 psi at 1100-1300 RPM, with the same 59 - 88 psi at 3500-4000 RPM.
 
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Discussion Starter #3
Engine had 3600 miles on it when bike was totalled. I got it as part of the race kit. The thing that concerns me is the milky color the oil takes on when it runs. Does the oil pump go bad on these? I rinsed the crankcase with diesel fuel twice and the milky color still appears.

It takes 2qts for engine to show full.

Should take a little over 3 quarts. Why is adding the recomended amount causing it to be overfilled?

I will get pressure gauge to check that problem. I used 2 different sensors and both of them give the same reading. Where could I be losing pressure?
 

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As a first step, remove the oil strainer that I mentioned in (D) of my first post. If that looks OK, then check the oil pressure relief valve as I suggested in (C) of my first post.

AS far as the cloudy oil is concerned, does it stay cloudy? Usually the cloudy oil window is from condensation in the crankcase, and as soon as you get a good bit of running on the motor and get the oil hot, it evaporates out that little bit of water and the window stays clear.

The oil filter holds some oil, and the crankcases too, when you drain the oil. I think the 3.1 liters is correct as long as you change the filter too.

How long did the engine sit?
 

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Does the oil remain cloudy? It sounds like it might be foaming ,air mixing with oil causing low oil pressure problems and clouding when running. Could be a leak in the pickup tube or bad gasket on oil pump. Good luck Tim
 
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Discussion Starter #6
Combination of problems! :eek:

A) It was a stuck relief valve

B) It was a crappy-O ring on the oil pump

Thanks for all your help!

She's purring like a Duc.. any suggestions on an oil pressure gauge that I can put on permanently? I would like to eliminate the idiot light and go with real time information!
 

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These guys have a good selection of gauges (as well as nearly everything else!):
http://www.mcmaster.com/

"hotrod" car accessory places usually have a decent selection, but usually it's bigger gauges...

I'd recommend using metal line or braided stainless line, I've never trusted the wimpy nylon line that comes with most car gauges. If you use the braided stainless, make sure it can't rub on anything, with vibration it acts like a file...I've got FHE on that.
 
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