Topic: Oil Cooler or Not?

[DennyK]

Folks,
Putting our 1974 750K back together and I am wondering if I should re-install the Lockhart oil cooler that some PO put on the bike.  As you can see the cooler has been squashed a bit on the bottom, but it did work when we road tested the bike, before we tore it down for the build.  It looks pretty easy to remove the lower portion on the block and forget the oil cooler.  I saw a couple of old used coolers on EBay.  Just wondering what advice some of you may have.

[Davidov]

I have an adapter on my oil filter location.
It converts to a spin-on filter and has outlets for cooler lines.

I have yet to get a cooler, but I think I will after fixing up a few other things.

If you think you'll be riding in high heat summer weather or stopped at traffic lights, a cooler is wise choice in my opinion.

[70CB750]

Some people use oil coolers, some believe they are not needed.  Do a search, it was discussed before.  I think majority goes without oil cooler, even guys with over 100 000 miles on the clock.

[oldhatt45]

DennyK,

I have the very same Oil Cooler setup on my K6.
Has been on my bike since it was brand new.

If you decide to take the Adapter off, please don't just throw it away.
They are hard to find in the original form and there are many that would buy it in a heartbeat.

That said, I do like having it on the K6 especially in the Summer.

Charlie

[Bodi]

"I have an adapter on my oil filter location.
It converts to a spin-on filter and has outlets for cooler lines.
I have yet to get a cooler, but I think I will after fixing up a few other things."

Curious about this. Adapters route the oil flow from the engine to one hose fitting and to the filter from the other hose fitting.

Do you have a hose connecting the two fittings to allow oil flow?

[RRRToolSolutions]

Honda did a great job of designing the cooling fins and oil flow for the stock CB750. In stock form, these are under-stressed and will live for almost ever. Fresh oil of the correct grade and viscosity are far more important.

Now, if you've got a side-car, one of those big Vetter Fairings, haul two-up, or run for long periods in extreme high temps - I'd say good idea. The downside of some installations is the lack of thermostat control. Too Cold is a problem too. An engine needs air, fuel, and temperature to have proper combustion.

I have one on my hot-rodded 836, but I will tell you that it's probably doing more harm than good. Mine is a Honda factory cooler from a CB650 Nighthawk with one of Terry's adapters that uses a K&N Chrome spin-on filter. It's a nice set-up, but using my little RayTek infared gun, I get 160 F on the oil cooler after a 30 minute ride. The temp goes up a little on longer 1 and 2 hour rides, but the highest I've ever measured was 180. The problem with that is it should be in the 190/200 range. Just look at the newer water-cooled bikes and you'll find that 190~210 F is their targeted range - this promotes clean burn and more power from your engine. If your bike is making more power running cooler - then there are some jetting problems.

I would not install one unless you have some extreme operating conditions in mind. Cooler is not better -

Best Regards, Gordon

http://www.rrrtoolsolutions.com/articles/honda-1974-cb750-four-cb750k4/

[strynboen]

a oil cooler dont Work vhen the bike is standing still. or drives slow.it need a elektric blower and a termostate..to funktion perfekt. in a traffic jam etc...
.this komplikates the simpel idea..
mine bikes have been hot once in 4 years..so hot i start smell the leaking oil at the head ...but still the bike run perfekt

[na3s]

Splice a themostat switch into the oil lines going to the cooler. The oil will auto bypass the cooler when cold

[70CB750]

Clever

Splice a themostat switch into the oil lines going to the cooler. The oil will auto bypass the cooler when cold

[SOHC4 Cafe Racer Fan]

If you are in a warm weather region, like the Southwest US/SoCal AND you are using an overbore kit, a cooler is a good idea. 

I am using a Seatrab.  My current 836 runs on the warmer side without one on hot Summer days.

[Mitchell]

When i bulit my turbo set up on my 750 i put an oil cooler on cause turbos like to get real hot and was always under the impression i needed it. there is no where to mount the cooler it self cause of the turbo and header being all in the way to mount it up high where you would normaly mount one so i mounted one down low and it only took about two weeks for a rock to fly up and busted it, well i took it off on the side of i 20 on the way to the batber vintage fest and left it. It took me 2 years before i put another one back on and ive never had a problem. The one i have on it now is very small and mounted off to the side on the motor mount and its on there more for show then its cooling abilities. My sandwich adapter has a t-stat in it. I think oil coolers look awesome so to me its more of a looks thing and im sure if you leave it of you will never have a problem and if you put it on it will just look trick.

[754]

Dont measure the cooler temp,measure temp in the oil tank..sounds like the cooler was working..

[RRRToolSolutions]

Here are some pics of the Nighthawk cooler I've got on mine. Again, I don't think my bike needs it since I'm not beating on it. As some say though, it is something to look and talk about.....

This bike also has a Gordon Frame Kit - Model #1. You cannot see it once installed, even from underneath. Gordon/RTS

[Old Scrambler]

Sanitary..........you missed a spot on the inside of the fender

The oil cooler would be a LOT more effective if mounted higher and farther forward..............otherwise they are 

[Retro Rocket]

Dont measure the cooler temp,measure temp in the oil tank..sounds like the cooler was working..

Bingo, I was going to state this earlier...  I have NEVER seen an engine failure attributed to an oil cooler, I always use them and so did most air cooled bikes built after the old SOHC bikes. If anyone is really worried, use a thermostat..

[socal1200r]

Altho I don't have an oil cooler on my CB650, I did put one on my 2014 Yamaha Bolt.  I decided to go with a vertical cooler, like they use on Harleys.  I don't ride the CB650 all that much, but if I did, I'd probably invest in an oil cooler for that bike as well.  My Aprilia RSV has a factory oil cooler, so right now the CB is the only one missing.  While on the subject, does anyone have a source for the oil filter adapter plate/fittings that would fit my '79 CB650?

[DennyK]

Hey Guys,
Thanks a ton for all the comments.  I did decide to remove the old Lockhart oil cooler system.  It took a 32 mm socket and breaker bar to get it loose, but no damage, the stock oil filter parts went right back.  I am pushing to get our build done, but will likely sell the old Lockhart system.

Denny K