R90/6: Oil cooler or Oil Pan "deep sump" spacer?

[banzaibob]

This winter, my R90/6 is going to feel the wrath of my wrenches. I intend to install a Seibenrock kit and rebuild the heads. Question: Should I find an oil cooler conversion kit (who makes them, by the way?) or should I just opt for an oil pan spacer to increase my volume? I know that the R100 was the only airhead that used or needed an oil cooler. After the build, I assume that because of the increase in power I will have the same needs as an r100 as far as keeping the oil temps under control.

From what I have gathered, converting it to an oil cooler is far more complicated that bolting on an r100 manifold. And using the oil pan spacer is complicated as far as modifying your center stand. Who has experience? Come forth!

 

[beemerphile]

The biggest complication is removing and replacing the oil filter sleeve in the block. Not so bad with the block in an assembly stand, but I'd think a challenge in the bike. The shame is that you lose the simplest oil change of all airheads - and NO $2,000 o-ring! Most will say that you don't need it unless you run the 7rock hard - as in race it. I have not found the oil coolers to do much good in traffic tie-ups (parade duty) because there is no fan to force air thru them when stopped. I have a Siebenrock kit for my 76 R75 that I plan to install with dual plugs if the top end ever needs refreshing. I put a 3 quart Mac oil pan on it that I had on my 77 RS. The RS will get a spacer ring with the current rebuild. I plan to run both with 2-1/2 quarts of oil and the fill level dropped a bit to reduce windage.

If I installed a cooler it would only be after I determined on my own bike and with my own pattern of use that it was necessary. Otherwise, why put up with the aggravation and expense? You might want to install an oil dipstick thermometer for a while to see how your oil temps are running. I don't like them for steady use because they are are to read and inflexible, but I have one that I swap in when I want to do an oil temperature study. You are welcome to borrow it for a week or two for postage if you want to do likewise.

 

[20774]

I know that the R100 was the only airhead that used or needed an oil cooler.

You make it sound like every 1000cc Airhead got an oil cooler. Obviously that's not true. I have never felt the need for any kind of additional oil cooling on my /7. As suggested, if you were to run it very hard especially in high external heat, pull heavy trailer loads, or do a lot of commuting, maybe. Save your pennies and wrenches for something else.

 

[bob_m]

I put an oil cooler on my 84 R100 when I freshened it a few years ago. The oil changes became a real PITA. I subsequently removed the oil cooler. Granted, I did not have high performance bits on the engine, And the bike was ridden exceptionally hard, but there was never a real reason to install it in the first place. I have heard that bikes run a little cooler running synthetic oil.

Good luck with your project.

 

[lkchris]

The bikes that needed the oil cooler were the 1000s with the big valve heads. With that much material gone, they warped. Good idea on R100GS, too, due to high rpm at low ground speed.

 

[banzaibob]

I intend to use the bike for street applications, no racing. The votes appear to be in and it looks as if an oil cooler is more trouble than it is worth. So......any recommendations as far as an oil pan extension? I assume that sine the R90 is bone stock that it will require modification to the center stand. Anybody got a handle on that? Does it require cutting/welding?

 

[pauls1150]

Not your bike but directly related: I installed deep oil pans (with the extended pickups) on two of my airheads (no R90) and had zero issues with the centerstand clearance. Note that the deep pan (or the pan spacer, which gives you another big gasket to potentially leak) not only increases capacity, but the additional exposed surface area also increases cooling.
A very good friend with an R90S insists on keeping his bike absolutely stock... and it will NOT handle the traffic jams here in the summer, it WILL overheat.

 

[pglaves]

I forget what they were called, but I was partial to the spacer that had tubes in it, front to back, through which air could flow to aid cooling. Corks in the front of the tubes in the winter avoided over-cooling.

 

[20774]

A variety of oil pans at the bottom of Anton's page:

http://www.largiader.com/tech/oilpan/

 

[rolyak]

Pan spacer w/three tubes

FWIW My '77 R100S with about 80K has that set up, I've only had the bike for a year so unsure if it really needs the extra cooling? I replaced the Reynolds Ride Off stand that did not interfere with the spacer however I wanted the OE center stand so I had to relocate the interfering cross brace. While replacing the pan gaskets (that had an excessive application of Hylomar, that congealed in balls around the pick up, and some made their way to the filter) I discovered the steel pick up had only one bolt holding it in place. Additionally the steel pick up experienced numerous fatigue fractures (from vibration).

Should you decide to go this route be sure to make sure the pick up bolts have sufficient thread engagement, both of mine were too short!

 

[barryg]

I forget what they were called, but I was partial to the spacer that had tubes in it, front to back, through which air could flow to aid cooling. Corks in the front of the tubes in the winter avoided over-cooling.

Paul, they were the Briel oil cooler. I've been running them on my '74 for 25 years, I guess they work. Never plugged them in the winter due to the Mid-Souths mild winters, although I have thought about it. It came on the bike when I bought it. I've rode the bike over 100,000 miles and the cooler never gave me any problems. Probably the only real down side is you lose a little ground clearance. The bike has evolved over the years from a nondiscript /6 into what I call, a bike with a cool look. The 3 hole cooler is one of the many features that gives the the bike a distinct period look.

 

[AntonLargiader]

I would just go with the stock deep sump and matching pickup and dipstick. It has better baffling to keep the oil around the pickup, the pickup head is not prone to cracking, no spacers are needed, just one pan gasket, and it's simple/light.

 

[barryg]

I would just go with the stock deep sump and matching pickup and dipstick. It has better baffling to keep the oil around the pickup, the pickup head is not prone to cracking, no spacers are needed, just one pan gasket, and it's simple/light.

Anton, I understand what your saying. I used to work at a shop that serviced all German brands of cars and BMW motorcycles. Just normal day to day service, concours resto's, racing and performance applications and upgrades. Two of my specialties was headwork and general BMW motorcycle service. Our customers knew we did a lot of performance work on cars and bikes, so I got a lot of questions about this and that to do to their cars and bikes. I talked more of my customers out of doing things and to leave things as is, than doing all the so called upgrades. Some people see the beauty of a stock BMW, others see it as a base starter kit to start upgrading and farkleing. . One guys gets a bike and adds all the stuff , the next guy gets it and can't wait to remove it. It's a truely funny, never ending cycle.

 

[jforgo]

Oil volume/air volume

The RS will get a spacer ring with the current rebuild. I plan to run both with 2-1/2 quarts of oil and the fill level dropped a bit to reduce windage.

.

I often see this sentiment regarding deeper pans on Airheads; using them as a way of increasing air, rather than oil, volume. People say it will reduce blowby/air pressure in the engine.
So, when you run a half quart low with a larger pan, you are increasing the internal air volume roughly 500cc's. But what are we comparing this to? What is the internal air volume of an Airhead to start with?

 

[20774]

So, when you run a half quart low with a larger pan, you are increasing the internal air volume roughly 500cc's. But what are we comparing this to? What is the internal air volume of an Airhead to start with?

Maybe think of it this way. When the two pistons of an R100 come from TDC to BDC, they will be displacing 1000cc. By increasing the internal air volume by 500cc with the deep sump, you've created a larger space for that to be "absorbed" into. No matter the case, the crankcase breather is supposed to help alleviate this situation. But it can transfer only so much air due to its size. So, by increasing the internal air volume by 500cc, you've reduced the amount of air that needs to be pushed out the breather on each cycle. That will tend to relieve the amount of oil mist that might also be expelled.

 

[8ninety8]

Deep pan or regular, with the stock dipstick the internal volume of air can be checked simply by looking at the dipstick. does that make any sense? I guess with a deeper pan the oil level can run closer to the bottom mark with less danger of sucking air thus increasing the internal crankcase air volume??

 

[47512]

25 years ago I found a hot deal on a OE BMW oil cooler kit. I installed it on a R75/6, with the original 2qt oil pan. I would reach down from time to time and touch the cooler to see if it was working, it rarely got hot.

So I installed a VDO oil temp gauge to see what oil temps were. Most of the time the oil never got hot enough to open the cooler. On a hot day on the freeway or sitting in traffic the cooler would open a about 210deg. One time in Death Valley when it was over 120deg, the oil temp got up to 250deg. Still not hot enough to ruin good oil.

I still have the bike and the cooler is still on it, I removed the oil temp gauge long ago as I don't worry about oil temps any more. The old relic has 175,000 miles on it with no probblems, so I guess it's been happy with the oil temps.

It is a pain to change the oil filter because of the clearance issue between the thermostat and exhaust pipe, I've done it many times, it just takes alittle more time.

In my opinion the old twins don't get their oil hot enough to warrant installing a cooler.