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Author Topic: Oil Cooler Question - do Honda OEMs restrict flow?  (Read 1362 times)

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Offline raymond10078

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Oil Cooler Question - do Honda OEMs restrict flow?
« on: December 02, 2011, 05:13:53 PM »
Please - let's not let this become a discussion of whether our bikes need one or not!

I see that some use newer Honda OEM oil coolers.  In looking at the oil lubrication system for many of these bikes (with oil coolers), I see that the oil cooler had a separate discharge from the oil pump, with the oil cooler loop dumping back into the sump.  The oil to the bearings was not routed through the cooler.

So, that got me wondering about the oil flow capabilities/restrictions of the newer (as in CB650's 750's, 900's of the eighties) oil coolers.

My question is:  has anybody noted a significant drop in oil pressure (as in before and after comparison) when using one of these OEM coolers? 

My question is based on what appears to be smaller inside diameter tubing used on these OEM coolers - when compared to the original Lockhart coolers (that were marketed for our SOHC 750's).
« Last Edit: December 02, 2011, 08:23:02 PM by kandrtech »
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1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline FuZZie

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Re: Oil Cooler Question
« Reply #1 on: December 02, 2011, 05:20:33 PM »
Quote
My question is based on what appears to be smaller inside diameter tubing used on these OEM coolers - when compared to the original Lockhart coolers (that were marketed for our SOHC 750's).

Wouldn't the smaller diameter equal increased pressure in the cooler?  Maybe reduced flow?
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Offline raymond10078

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Re: Oil Cooler Question
« Reply #2 on: December 02, 2011, 08:21:52 PM »
The basis for my question is the expected reduced flow.  The oil "port" at the oil filter (on the engine block) is certainly larger in cross-section that the "ports" of the Honda OEM coolers - thus the question.
« Last Edit: December 03, 2011, 03:36:13 AM by kandrtech »
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1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline MCRider

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Re: Oil Cooler Question - do Honda OEMs restrict flow?
« Reply #3 on: December 02, 2011, 08:23:36 PM »
Put a gauge on it and see. I doubt it.
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Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline MCRider

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Re: Oil Cooler Question - do Honda OEMs restrict flow?
« Reply #4 on: December 02, 2011, 08:24:23 PM »
Oh, my bad. You may not have it yet. Never mind.
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Ride Safe:
Ron
1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline FuZZie

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Re: Oil Cooler Question - do Honda OEMs restrict flow?
« Reply #5 on: December 02, 2011, 09:17:32 PM »
It comes to mind that restricting flow trough the cooler could be done to match heat dissipation of the rad? like surface area vs flow. I'm only guessing but I think the exposed surface area of the rad could be could be a factor.
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Offline Kanticoy

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Re: Oil Cooler Question - do Honda OEMs restrict flow?
« Reply #6 on: December 02, 2011, 09:53:13 PM »
I dunno about the stock units.  I have a vintage Lockhart for my cb400f and the lines coming out of the filter adapter are the same as the ones going into the cooler. 

edit:  meaning the outlet nipples vs. the inlet nipples.
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Offline bwaller

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Re: Oil Cooler Question - do Honda OEMs restrict flow?
« Reply #7 on: December 03, 2011, 07:24:45 AM »
I'm using a 80's CB650 cooler. The original adaptor plate has a 10mm bypass hole so not all the oil flows through the cooler. I was torn over whether or not to do the same but decided against it. I'm using a 650 oil pump and was concerned about the opposite, pressure maybe too high especially on start up. I mounted a guage at the pump for the initial run in and the pressure was +- 70lbs at operating temps. & 5000 rpm.

On teardown after one season of serious flogging the engine is clean, cam & rockers are still like new, certainly no lubrication issues.
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