Oil Cooler System on a 1979 CB750K

[sgtslag]

http://s1136.photobucket.com/albums/n489/SgtSlag/Oil%20Cooler%20Project/

Not the best for organization, but it gives a pretty good look at the system.  I need to hook up a pressure gauge to see what effect the System has on oil pressure, but otherwise the System is done.  I have 1,500+ miles on it, no leaks, and the oil temperatures dropped from 250 F, riding two up @ 55 MPH with full saddlebags and trunk (riding on a trip for 5+ hours, 250 F average temperature), to ~210 F, same load, same time, same speed.

It is less expensive to install a cooling system by replacing the oil pan with one from a CB900, but I did not know about that until recently.  The Oil Cooling System I have, was installed in Spring of 2010.  This complete system cost me around $220 in parts.  That includes everything, including the oil temperature gauge, which is purely optional.  The Thermostat is not required, but it makes it much easier, and faster, as the oil warms up quicker, and I only have to cover/uncover the Radiator when the air temperature gets below 60 F, and I am not running at highway speeds (the oil/engine never reaches operating temperature below 60F, riding around town).

The real value of this Cooling System is that it will extend the life of the engine.  Seals and gaskets degrade with high heat (hardening).  Dino oil breaks down into carbon and varnish at temperatures above 250 F, as well.  This System saves the engine internals, as well as extending the life of the oil.  Besides that, it was a very fun project.  Cheers!

[Re-run]

Where did you get the parts for that or did you make them?

[sgtslag]

All of the parts were purchased.  The spin-on filter adapter with cooler ports, was made by a now-out-of-business machine shop.  The Oil Thermostat is made by Perma-Cool Company, #1070 model with 1/2" oil paths.  The Radiator was purchased off of e-Bay, it came off of a Honda CB900C motorcycle.  The only thing I made, was the mounting bracket, which was aluminum bar stock, cut to length, drilled, and U-bolted to the frame.

If you are asking whether it was a kit, or did I put it together on my own, the answer is the latter.  I studied oil cooling systems on other bikes, and then I assembled the parts I wanted in my system.  I went through a bit of hose length before I got it right.  I installed the Oil Temperature Gauge so that I could demonstrate the value of the system with scientific facts (real world numbers), rather than assumptions, and conjecture.  The Temperature Gauge also serves to help me monitor the engine in slow traffic situations, to avoid overheating.

[DesignBuild]

(82' CB750F)

Could you elaborate on what you mentioned about the cb900c oil pan conversion being cheaper? I've been interested in putting an oil cooling system on my bike for awhile but the only thing i ever find are things like cycle X's SOHC converter (similar to what you've done here from what i can tell). Although this is basically the spark of inspiration for actual research.

Did the 900C's oil pan have the leads for the hoses stock? And do you happen to know which pans swap out between which models?

Awesome job though.

Thanks.

[sgtslag]

The CB900C had an oil cooler, stock, from the factory.  My research into using this bike's oil pan is in the early stages.  It is mentioned in another forum, as being less expensive than what I did.  However, there are several caveats:  the 900 uses a dual oil pump, with one pump pushing oil up the cooler, and the other, larger pump rotor/impeller, pushing a larger quantity of oil up to the engine.

I have been told that the CB900's cooling lines have no impedance to oil, and that there is both low pressure, and low volume, in its oil lines.  From the FSM's diagram, the gentleman is correct in that it has relatively low pressure.  It also has no thermostat to bypass the radiator when the oil is cold.  To use the CB900's system, you would need to use its oil pump, as well.  It simply pumps oil out of the sump, into the radiator, and back to the sump.  It is not pumping 100% of the oil through the radiator for cooling, it just bleeds off an unknown amount to the radiator, which is less efficient.  It really mixes cooled oil, with hot engine oil, in the sump, which is not my idea of a good way to do it.  Without a thermostat, I suspect the CB900 takes a while to warm up...

The dangers my system has, according to a very knowledgeable CB900 owner, is that I am using the radiator off of a CB900.  This radiator, and hoses, are not designed to be used in a high pressure system.  I wonder, therefore, how much pressure the radiator, and the OEM hoses on it, are rated for.  I have 1,500 miles on my system, and I check the cooling system for bulging hoses, and oil leaks, before every ride -- nothing yet.

The old Lockhart systems were apparently known for blowing hoses due to the 71 PSI generated by the CB750's oil pump.  They also were known for blowing their hoses off of the hose barbs -- USE T-BOLT HOSE CLAMPS ONLY!!!

I will report back here when I find more on the CB900's cooling system.  This gentleman states that it actually flows a very low volume of oil through the radiator, and that it provides little cooling to the CB900!  I really need to learn more of it before I worry about replacing my radiator with something else.  Cheers!

[DesignBuild]

Considering all that, it does sound significantly less efficient than your set up, which would equate to a waste of time to do the 900 conversion if true in my opinion. The difference in cost just doesn't seem to be all that much of a deterrent between your system and the conversion if yours has the efficiency to justify the work. I look forward to what you find out.

As far as the radiator and hoses from the 900 on your system goes, i suspect the 900C manual might (should) have it's oil pressure rating somewhere in there; as for the hoses, that info should be printed somewhere on them and if not you could always swap for a higher PSI rated line at a hardware store. You've driven quite a bit on them so far, and it sounds like they are doing fine, but only extensive wear and tear would tell.

[sgtslag]

You are correct:  I found the flow volumes, and the main oil circuit's oil pressure, listed in the FSM for the CB900.  Here is what I found:  FSM (page 2-6), clearly shows that the dual oil pump is a rotor type (rotor oil pumps are high pressure, and high volume); page 2-1:  Engine, 43 US qt/min. @ 7000 RPM; Cooler, 19 US qt/min. @ 7000 RPM; 78 PSI at sensor (produced by the main circuit of the oil pump, coming out of the filter, going to the engine).  The CB900's cooler flows around 44% of the volume flowing through its engine oil circuit, which is nearly one-half the volume pumped through the engine.

Changing the oil radiator hoses is challenging:  Honda used a proprietary connector type, which I could not find anywhere.  It would be easier to replace the radiator, but it would also be costly, probably more than $100 in parts.

The radiator has narrow oil paths, which will increase the pressure in the radiator, and its lines.  The pump on the cooler is a rotory pump:  high volume, high pressure.  Honda engineers must have designed the hoses, and the radiator to withstand a fair safety margin of pressure.  Still, the weakest link is where the oil will leak from, if it leaks.  I suspect Honda used those radiators on other bikes, with different pressure requirements, as well -- cheaper to use one design for all, as opposed to making multiple designs which are not interchangeable.  A lot of assumptions on my part.

I would recommend using a non-CB900 radiator, to be safe.  I don't care to invest another $100+ in my system, unless I know there is a serious risk.  So far, I have not found evidence to support a dangerous risk.  I am comfortable, at present, with my choices, and my design.  Cheers!

[TOOLS1]

My 76 Hondamatic (which has even more oil pressure then a K, or F model) Has had a Lockhart oil cooler on it for decades now. Every once in awhile I have to tighten the clamps. I am planning on changing the hoses this winter, since they seem to be hardening. What are these T-bolt clamps you mention? Are they the type used on fuel injection systems?
TOOLS

[sgtslag]

Exactly!  The first T-bolt clamps I found, were for a car's fuel injection system (typically 40-45 PSI, largest was 16mm).  I had a tough time finding them in the 25mm-27mm size I needed for the Honda radiator's lines, though (1"/25mm OD, 1/2"/12mm ID).  These T-bolt clamps are da' bomb!  Nothing holds like they do, for a reusable clamp.  Be careful not to tighten them to the point of cutting into the rubber hoses...