I'm sure someone out there has the answers. OIL PANS & BMWs On the twin-shock BMWs; R65 and R80, what are the largest capacity oil pans that can be used? What oil pick up pieces are required? Does it make sense to consider the "spacer" that adds depth to it? I want to maximize the oil capacity of the engine (yes I know an oil cooler can).
I'm not sure what the maximum stock oil pan capacity is, I've seen a website somewhere that list that, along with dipstick info. Available as after-market items there used to be (and may still be) "three quart sumps" which nominally increase the oil capacity by one quart, to 3 quarts, and have an oil pickup extension (this was from the /6-/7 days). In theory, added oil pan area gave cooler oil, but in practice it wasn't but a couple of degrees cooler. I have one on my /5, and it's primary use has become to lower the oil level in the crankcase by a cm or two, thereby giving a but more ullage volume and much less tendency to blow oil mist out of the crankcase breather. I also use a later-model dipstick, which is a little longer and gives the "correct" reading when checking the oil level (which gives an oil volume of 2.75 qt, up from 2.0).
The maximum stock Airhead capacity is 2500cc, or 2750 cc with the oil cooler added to that. If you're serious about heat in your oil, the first things to do are ... 1. Use synthetic motor oil 2. Fit nikasil cylinders Compared to those, a few ccs more oil capacity is of way less benefit. And, of course, the only Airhead that has worries as regards oil heat is the R100 ... and obviously that's the only one ever factory fitted with the oil cooler. Also, there wouldn't have been an R80G/S were it not for nikasil cylinders.
Here on the idiotnet (not that any of us right HERE on the idiotnet are idiots!), there seems to be a popular consensus that more oil is a waste of space. There are very real reasons why our bikes have as much oil capacity as they do and not half as much. I have worked on race airheads that needed increased oil capacity. It was absolutely essential. One of the biggest advantages of increased capacity that is rarely mentioned is the fact that with increased capacity, the oil goes through the pump less often. The pump itself heats the oil considerably! Many a tuner has got more power to the ground AND decreased oil temps by downsizing the oil pump. I have worked on one such airhead. Lowering the sump level away from the crank is often a good thing when you have the room but don't forget that these engines are plain bearing engines. There are VOLUMES of oil squirting out of those rod and crank bearings like putting your finger over the end of a garden hose. All that oil squirting out becomes a big blob of oil that hangs around the spinning crank and rods and actually pulsates and moves around. ALL the while this blob is loosing as much oil as what is going into it from all the oil squirting out of the plain bearings. ALL that oil is up there and ALL around your crank breather until your sump level gets down below the oil pickup. I don't recommend lowering your sump's oil level that far! Your right rod big end is sure to go first and other things will follow!
Back then, we found that the oil level would drop to about mid-point on the dipstick and stabilize. Ending up with an oil level 1-2 cm lower than "full" and a capacity of 1.7-something quarts. That sump song-and-dance at least got the oil pickup submerged a better amount and bumped the oil capacity back to the design-level. Also it was argued that more oil capacity was good, since more oil volume allows more contaminants to be assimilated. But whatever. It's worked well for 30-odd years...
Usually I am backing up my opinions with the experience I have gained through working on tons of airheads. My opinion on stabilizing oil usage is largely based on my personal experience with three beemers I have logged a lot of miles on but my opinion does rest some on customer reports. All three of my own beemers have had good, tight top ends and I have never noticed my oil usage stabilize at the half way mark. My bikes will go below the half way mark about as fast as they get to it. I have heard many similar reports from customers although I haven't any way of confirming it. I have seen quite a few airheads run completely out of oil. I hope they didn't think they were going to stop using oil at the half way mark!!
GREAT description of the physical state of the oil in operation. The older bikes are even more dependent on the agitation factor. Low pressure oiling wants to be dipping into the bath...the R60 deep sump doubles the capacity 2 to 4 qts, but still requires the oil pickup "extender".
The later model oil pans were the highest volume, and they had a baffle to prevent oil migration to the front of the pan under really hard braking. The later oil pickup had an integrated extension requiring only one gasket. The above could be combined with one of the sump extensions, assuming adequate centerstand clearance. Some say additional oil capacity offers little benefit, but it doesn't seem like it could hurt anything.
You must be talking about iron cylinders. My RS with nikasil cylinders and about 75K miles has never needed me to check the oil level between changes. My G/S on the other hand shows a little oil consumption, but of course it's always running 1000 rpm faster than the RS. Again, if you're worried about heat and oil consumption, in this order 1. Use synthetic oil 2. Fit nikasil cylinders 3. Fit oil cooler 4. Fit larger oil pan
No, I am not talking about iron cylinders. I am talking about iron cylinders AND nikisil cylinders. Believe me, if you rev them enough, ANY beemer is going to use some oil one way or the another. If I was worried about heat, I would recommend your suggestions in reverse. If I was worried about consumption, I would freshen up my engine.
Interesting...I have a few R80G/Ss that can go 5-7K miles between oil changes and the level never changes. All are Nikasil 800 or 1000cc engines and live at redline quite a bit. I just took one engine down that had 35K miles but that was not because of oil consumption. No oil coolers...just good old Mobil 1 after the rings set.
