Author Topic: Oil Pressure  (Read 554 times)

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Offline FTBY55

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Oil Pressure
« on: October 11, 2019, 03:41:56 PM »
 Have a '96 FLSTF that I think needs a new oil pump. Factory manual says 15 to 35 PSI @ 2000 rpm. Running 20W50 Amsoil Synthetic and I don't see over 22 even up to 4000 RPM.
Cruising at 3500 and I'm lucky to see 22psi. If I stop at light and idle it goes down to 10-12 cold after heated up to 100 deg. it will drop to Zero at idle.
Looking for suggestions/ recommendations. Considering an S&S High Pressure High Volume replacement.
When I tried 20w60 I did see 60 psi cold, could I have overpressurized something and now be bypassing oil somewhere.

Offline Deye76

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Re: Oil Pressure
« Reply #1 on: October 11, 2019, 04:00:57 PM »
The oil light on my old Panhead would flicker at traffic lights, ran it like that for 11 years, then sold the bike still going strong. 
East Tenn.
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Offline thumper 823

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Re: Oil Pressure
« Reply #2 on: October 11, 2019, 04:06:41 PM »
Some people install a stronger Pressure relief spring.
Some say it is bad.
Some say it is good...I have not ever checked the oil schematic .
I did it about 5 years ago and 20K miles back.
The results have been spectacular.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Amateur engineering with bad math.

Offline FTBY55

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Re: Oil Pressure
« Reply #3 on: October 11, 2019, 04:23:48 PM »
thumper 823,

 It seems when the oil gets hotter pressure drops. 20W50 thinning out, just changed and less than 200 miles on it. Oil oil pump springs, ball check and screen recently changed.

Offline thumper 823

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Re: Oil Pressure
« Reply #4 on: October 11, 2019, 04:42:58 PM »
Most oils (if not all) have the same pour points after heated up..
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
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Offline Ohio HD

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Re: Oil Pressure
« Reply #5 on: October 11, 2019, 04:55:42 PM »
I'd ride it.

Unless things change, or you have noise, ride it.
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Offline Thermodyne

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Re: Oil Pressure
« Reply #6 on: October 11, 2019, 06:00:11 PM »
What /\ he said.  Just ride it, anything over 7 is fine for an Evo.


Offline Hossamania

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Re: Oil Pressure
« Reply #7 on: October 11, 2019, 07:56:26 PM »
How old is your gauge? What did it run in the past, when did it change, did you notice a difference in running or sound when it did?
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Offline FTBY55

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Re: Oil Pressure
« Reply #8 on: October 12, 2019, 01:28:00 AM »
Gauge is new, changed out twice as the first leaked. second was supposedly reading incorrectly. shop confirmed this one with their gauges. Bike used to run twenty PSI higher and had hit sixty on startup. Now 22 to 25. The drop to 0 on warm idle worries me. Been doing some research and realized I can't do a full change out without removing engine. Will have to use existing drive shaft. Oil returning to tank is well aerated, Many little bubbles. Wondering if I am somehow getting crossover, internal leaks..

Offline thumper 823

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Re: Oil Pressure
« Reply #9 on: October 12, 2019, 03:40:03 AM »
Try a new Oil Pressure relief valve spring.
As i said, a new slightly stronger one fixed all my low P problems.
D Troop 3/5, - C/16 ,162AHC, Mekong delta.
Amateur engineering with bad math.

Offline hbkeith

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Re: Oil Pressure
« Reply #10 on: October 12, 2019, 05:47:26 AM »
I'd ride it. :up:

Unless things change, or you have noise, ride it.
       :up: Hell , my last EVO bagger with a gauge ran at barley over 5psi at idle when hot , was like that for 50000 miles , its a Harley

Offline Dan89flstc

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Re: Oil Pressure
« Reply #11 on: October 12, 2019, 05:52:52 AM »
Throw the oil pressure gauge into the scrap bin, or keep it as a tool, but take it off the bike.

If the pressure is too low the lifters will tell you right away.

Don`t wast your money on the S&S high volume pump, it is unnecessary.
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Offline FTBY55

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Re: Oil Pressure
« Reply #12 on: October 12, 2019, 08:02:06 AM »
Try a new Oil Pressure relief valve spring.
As i said, a new slightly stronger one fixed all my low P problems.

 I replaced the spring and check this spring with no change. Does somebody make a higher pressure replacement?

Offline thumper 823

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Re: Oil Pressure
« Reply #13 on: October 12, 2019, 01:05:07 PM »
Ebay.
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Offline screem

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Re: Oil Pressure
« Reply #14 on: October 12, 2019, 03:40:06 PM »
Throw the oil pressure gauge into the scrap bin, or keep it as a tool, but take it off the bike.

If the pressure is too low the lifters will tell you right away.

Don`t wast your money on the S&S high volume pump, it is unnecessary.

I made the switch to Synthetic Oil on my evo some years back .. same issues as the OP a guage that would read zero at hot idle, changed the spring, to a little higher pressure spring with little to no change... the red idiot never ever came on and the lifters never got loud. I changed the guage out with same result of zero/hot.
   Just to make sure there was no other oiling issue, i dropped the synthetic oil and filter and put 20-50 dino oil back in it and the oil pressure went to 8lbs at hot idle, and 28 or so running on the highway.
   I have never put Synthetic back in it... over 150,00 miles, took top end off 110,000, everthing looked great, cleaned up the jugs, re-ringed, new studs and slapped it back together.
   

Offline thumper 823

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Re: Oil Pressure
« Reply #15 on: October 12, 2019, 04:14:59 PM »
I use amsoil and have zero problems
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Amateur engineering with bad math.

Online Burnout

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Re: Oil Pressure
« Reply #16 on: October 12, 2019, 04:21:41 PM »
Often incorrect application oil light switches are substituted for the Low Pressure Switch used on a HD.
The switch has to tolerate the high pressures found at start up yet only turn on the light at very low (3psi?) pressures.
I won't trust offshore light senders unless they specifically state the pressure.
There are many senders that look identical to a HD sender but have a different pressure rating.

Oil pressure gauges are useless. A 60 or 80 psi gauge will show zero at the low hot idle pressures seen on a HD.
A low pressure gauge will be damaged by the cold oil pressures at startup.
They don't call me Ironhead Rick just because I'm "hard headed"

Offline FTBY55

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Re: Oil Pressure
« Reply #17 on: October 12, 2019, 07:35:20 PM »
Replaced the pressure switch with new HD unit. Light would come on and not go off with rpm rise. 0 psi at traffic light. Took to shop and they replaced both new switch and new oil gauge that I had installed. Will see 25-30 on cold start, 28 mile run and gauge is staying about 22 at 3500-4000 rpm. When I stop at destination 0 on gauge , no indicator light lit. Start bike back up after a coffee and bagel and oil pressure is about 10 and takes a while to come up at 3-4K rpm. I see that they suggest a 0.40" shim for T/C plungers. Someone posted to add 0.20' shim to evo spring. Another suggested a #10 washer. Bought a few but they don't fit in plunger or cap. Put 2 #6 washers in and didn't see any real change so I sat down and decided to modify a 1/4-20 SS allen head bolt. I used a drill and file and took the diameter down until it fit smoothly inside the plunger. Next I took the head height down to 0.185" and filed the threads smooth o as not to bind on the spring. Inserted into plunger and placed spring over it. Hoping this will bring my hot idle oil pressure up to around 10 psi at idle.

Offline thumper 823

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Amateur engineering with bad math.

Offline FTBY55

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Re: Oil Pressure
« Reply #19 on: October 12, 2019, 09:02:32 PM »
 Thanks thumper, saw that earlier while searching.
Does raising the spring pressure starve the lower end and cam?  Any thoughts on ERT's adjustable spring pressure unit? 

Online Burnout

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Re: Oil Pressure
« Reply #20 on: October 12, 2019, 10:35:24 PM »
Replacing the pressure relief spring will not raise idle oil pressure.
It relieves high pressure it won't make up a lack of pressure.
They don't call me Ironhead Rick just because I'm "hard headed"

Offline FTBY55

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Re: Oil Pressure
« Reply #21 on: October 12, 2019, 10:51:57 PM »
Replacing the pressure relief spring will not raise idle oil pressure.
It relieves high pressure it won't make up a lack of pressure.


The mod I did just raised my start up oil pressure 10 PSI. Will try again tomorrow when cold.

Offline Benjie40

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Re: Oil Pressure
« Reply #22 on: October 13, 2019, 01:30:20 AM »
If the light ain't coming on at idle, your good to go... It's not a typical SBC with clevite 77 bearings on the journals. So it ain't gonna build pressure at idle.. 5-6 psi at idle is normal..

Offline thumper 823

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Re: Oil Pressure
« Reply #23 on: October 13, 2019, 02:57:06 AM »
Here is some things to think about in all of this -
With the Evo, HD said "dont idle it to tooo SLOW as it will be damaged because of LOw OIL P.
So by obvious deduction, assimilation, and a contraction or too,,we can deduce that no oil P for any reason at an idle is prolly a bad thing.
Being there are no flat bearings in an HD engine to actually create a hydraulic separation of parts using Oil P,  we can arrive that it is not engine tolerances issue causing the low readings once we have verified  no oil P..
If you have checked relief valves , springs ETC  and all is well, i would have to suspect a pump.
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Amateur engineering with bad math.

Offline MIKEL

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Re: Oil Pressure
« Reply #24 on: October 13, 2019, 04:30:23 AM »
Them old Detroit Diesel 2 strokes would run 5psi at idle hot and they had babbit bearings. Might try 60sae oil. I put Amsoil 60 sae in all 3 of my Twin Cams and Shovel.
Like what has been said if the valves aren't clacking Run it!!   


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