Results 1 to 7 of 7

Thread: Crankcase vent & oil usage? '78 R100/7 - other airheads

  1. #1

    Crankcase vent & oil usage? '78 R100/7 - other airheads

    I saw another thread that the poster had mentioned that he was experiencing oil coming out of the airbox, due to the crankcase vent.

    This aroused my curiosity to ask the rest of you this quesiton:

    How much oil does your bike use? I have had all sorts of advice here because when I fill oil to top of mark on the dip stick (with the stick sitting on top of the hole - as opposed to being fully screwed in) I use oil and it goes down rather quickly. I don't have any leaks, so my conclusion is that it is being "sucked" out and back into carbs and burned. However, the advice has been is to leave the oil level down somewhat (like to lower mark) and don't worry so much about it. It should use considerably less oil.

    In order to try to help remedy this, I purchased and installed a new "reed" type breather valve, but nothing changed in respect to oil usage.

    Someone else has also suggested oil usage due to worn valve guides which still could be, but I doubt it.

    Why? Because when I installed new Needle jets, and jet needles in my carbs the other day, the left carb was visibly saturated with oil, which could only have come from the air box through the carb tubes. Ironically, this was only visible in the LEFT carb and not the right carb.

    When discussing oil usage with Rusty @ Max's, he says that according to BMW, acceptable oil usage is approx. 1 Qt. per 600 miles - waaaayy too much to me. He suggested to simply run a lower amount.

    What do all of you experience in regards to oil usage and crankcase breather oil misting?

  2. #2
    Registered User kwb210's Avatar
    Join Date
    Jul 2009
    Washington, the state

    1/8 down

    I have a 1977 R100/7. For years I would arrive at the destination after any number of miles and check my oil in the morning. It was always down about half way on the dipstick. And I always filled it up. Then the next was down and repeat. It was suggested to me to add oil only to about 1/8 from the top add mark. The crankcase was simply building up to much pressure when she was full and it had to go somewhere. Now at 1/8 down from full I probably travel 4x the distance before she is down to 1/3 to 1/2 on the dipstick. Simple. Give it a try and see how it works. One danger on higher than normal crankcase pressure is the oil trying to get out somewhere that causes more damage like a camshaft seal! Right into the points area!
    1977 R100/7 1971.1972.1972.1973 R75/5
    1974 R90/6 multiple boxes
    Airhead Revival
    "Objects in the mirror appear to be losing" unk

  3. #3
    rsbeemer 22600's Avatar
    Join Date
    Jan 2011
    New Braunfels,Texas/Taichung, Taiwan

    Past reply to a thread

    I put a later mdl pan and pick-up on my '78rs only for the following reason, and I quote Largiader,

    "The deep pan and cast pickup are better than the earlier designs, so you can get more reliable oil delivery using the newest parts. Additionally, the greater air volume in the sump means less fluctuation in crankcase pressure and therefore less oil lost through the breather."

    My bike was blowing a lot of oil through the breather into the air filter area; the larger pan with the baffle seemed to help. I still use same amount of oil and dip stick as I did with the old pan. I just took notice where it came up to on the dip stick when I first changed it and added full oil change.

    You can find them on ebay or IBMWR Marketplace; just make sure it's '81 or newer and comes with the adapter and pickup parts.

    1978 R100rs MOA#22600 125cc Kymco , 180cc Kymco Racing King
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.

  4. #4
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    Early on with my /7, I thought I was using too much oil...a quart per 1000 miles IIRC. I put in Luftmeister 3-piece oil rings, but it really didn't seem to help much. When on long trips, I usually take 1-2 quarts of oil with me. I think I might have been adding a quart per 1500-2000 miles...I never really kept exact track...just as long as I got home with the amount of oil I was carrying. I wasn't religious about filling to the top when I filled, but during my long trips, I didn't really add any until it got below the one half mark. Then I'd usually more or less top it off. With the new top end, I don't have enough miles to know if that's going to change.

    One thing that I've read has to do with the additive packages...some oils tend to burn that off more quickly than others. That could be the reason for the dropping levels.

    Jimmy, does your /7 have the oil mist tube going to the left carb? That would be different for the '78s in my mind...mine only dumps to the right carb. If you had oil visible in the left carb and your breather output is to the right carb, then you might have bigger problems and it might have to do with the valve guides.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  5. #5
    jdubeemer jdubick's Avatar
    Join Date
    Feb 2008
    Boaz Alabama
    I have a 78 R100/7 with 55k miles and it uses very little oil. My very knowledgeable BMW mech told me that the MAXIMUM amount of oil to put in this engine is two quarts with oil and filter change. Look at your dip stick when it is changed and you will see it is at the full mark when screwed in and note where it is when not screwed in. Never fill above that amount or it will blow it out. According to him you can damage the engine by adding too much oil. This has worked for me for several years on several airheads.
    Jim Dubick
    Boaz, Alabama

  6. #6
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    Best way to deal with oil consumption IMHO is to fit nikasil cylinders.

    My '78 used oil and then I ran an '84 R100RS for 27 years and there was never any need to check oil as it was never low.

    Iron liner bikes put the heat in the oil; nikasil bikes dump it on your feet.

    Of course you should consume less using synthetic.

    Airboxes are not the issue. Keep the components in shape and then any excessive blowby is due to worn rings. You won't fix that with ventilation mods. You'll have way significantly less cylinder/ring wear with nikasil components, too.

    The late, angled front pan is a good idea, moreso with the 900s and 1000s. It's not clear the original motor design anticipated these changes. Comes with a spacer to lower the pump pickup and a different dipstick, of course. It's not about more oil, since if you fill to the same level you have the same air volume.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  7. #7
    Registered User
    Join Date
    May 2008
    B.P., MN
    always been curious about this, so, last spring made a crankcase breather expansion tube, fastened onto the right rear frame member and have been monitoring what collects in the tube. so far water with a hint of oil.Probably just what vapors off when cold. I check by removing a plug at the bottom. after a couple hundred mile ride just enough to wet a rag, maybe half an once. But it didn't go throughout the right carb.

    I also run a deep pan and 2 1/2 quarts. the deep pan at two and a half quarts gives more air volumn to the crankcase, as said by others, and seems to control crankcase pressure better than a topped up standard pan. I think a standard pan would run the same way If the level were kept to half way between full and fill marks. But then the amount of oil would be less than with a deep pan. '74 900.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts