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Thread: EGR question on a R75/5.

  1. #1
    Registered User 10drum's Avatar
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    EGR question on a R75/5.

    Greetings, I'm trying to understand the EGR on this R75/5. I have oil in the right intake tube. There's not much to that valve. Can that reed wear out?

  2. #2
    The valve is pretty trouble free. Some oil mist will be evident in the intake tube where the crankcase vent delivers the fumes/mist. If the amount of oil seems excessive then that would indicate excessive blowby past the rings. I would think that a compression test followed by a leakdown test would be in order.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://web.bigbend.net/~glaves/

  3. #3
    Liaison 20774's Avatar
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    To answer your question, yes the original printed circuit board material can wear out or chip, not to mention the spring that holds it down against the engine case. BMW came up with a reed valve which is less prone to wear out and is a direct replacement. Contributing to the additional oil mist can be a number of things. As Paul said, you could have significant blow-by on the rings causing oil to be further frothed up. Filling the oil too high reduces the air volume inside the engine casting which then promotes added mixing of oil and air. Dropping the oil a bit on the dipstick to say mid level might help. People add a deep oil pan (and pickup extension) but then only put in the original 2 liters of oil which increases the amount of air in the engine thus reducing the frothing.
    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!

  4. #4
    Registered User 10drum's Avatar
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    Thanks for the replies. This is a reed type egr. The bike has good compression 150# on both jugs. I installed rings less than 1000 miles ago. It was boarder line for a rebore. For this bike it was fine. As for a leak down test, I'm not sure if I have what I need to do a leak down test.

  5. #5
    Liaison 20774's Avatar
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    The reed EGR (for our bikes, it's really a crankcase breather valve) should be a good replacement...unless it's broken off and I suppose anything's possible! If you're working on a replacement rings, it's likely they have not seated in and you're getting extra blow-by which may slow down as the rings seat in. Plus new rings on a near need for a rebore, you might be on the ragged edge. See how things are in another 1000 or 2000 miles.
    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!

  6. #6
    Registered User ebeeby's Avatar
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    Simple first: The tube within the intake tube must be positioned correctly. If is is touching the intake tube, it will cause any oil mist to condense at a higher rate and congregate at the bottom of the intake tube, then dripping out the junction seams onto your garage floor, rather than being burned as part of the air mixture entering the intake from the intake tube. Tend to that first.

    Second: There is an upgrade for the crankcase vent valve, but the originals rarely fail. Telltale signs are chipping, and sometimes they gobble like a turkey. Inspect the valve for condition/freedom of movement.
    1973 R75/5

  7. #7
    Liaison 20774's Avatar
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    Looks like he's already upgraded...says he has the reed "egr".
    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!

  8. #8
    Registered User 10drum's Avatar
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    Mine does make a chirp sometimes when it is started, but nothing like it did before I did the top end. I was looking at the parts breakout, and I have the straight tube, with the right angle cap. I think the trap of upgraded hose should reduce the amount of oil to the carb tube, but that cap is $72. Man I like this bike, but the parts are a killer.

  9. #9
    Just for the record, it is PCV. The bike does not have EGR.
    Lee A. Dickinson - Danielsville, GA USA
    Airheads #3480 | Iron Butt Assn. #8914
    1976 R75/6 - 1992 R100RS - 1993 K1100RS - 2013 R1200GS

  10. #10
    Registered User 10drum's Avatar
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    Quote Originally Posted by beemerphile View Post
    Just for the record, it is PCV. The bike does not have EGR.
    Duh! That's correct. Positive Crankcase Ventilation. EGR is Exhaust Gas Recirculation. At least all involved knew what I was talking about. Out of curiosity, how was the airhead crankcase vented prior to the PCV?

  11. #11
    Liaison 20774's Avatar
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    Technically, the "Airhead" started with the 1970 models. It had the older round spring-loaded board covering the hole and moved up and down with changes in crankcase pressures. The /2s just before the /5 had a different mechanism. On the front of the engine is a rotating plate with holes in it. It was designed so that when the plate/holes reached the correct point, another hole in the case lined up, letting the pressure escape through the aligned holes. The pressure didn't vent directly to the atmosphere but ran through a series of channels until it came out of a small breather tube on the lower left front side of the engine block.
    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!

  12. #12
    Registered User 10drum's Avatar
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    Quote Originally Posted by 20774 View Post
    Technically, the "Airhead" started with the 1970 models. It had the older round spring-loaded board covering the hole and moved up and down with changes in crankcase pressures. The /2s just before the /5 had a different mechanism. On the front of the engine is a rotating plate with holes in it. It was designed so that when the plate/holes reached the correct point, another hole in the case lined up, letting the pressure escape through the aligned holes. The pressure didn't vent directly to the atmosphere but ran through a series of channels until it came out of a small breather tube on the lower left front side of the engine block.
    Similar to the Triumph twins, there was a rotating disc on the end of the intake cam.

    Thanks for all the replies. I really like this bike, it may be the best all round bike I've owned. It's great on the highway, as well as the back county roads here in Illinois. I'll ride it a bit longer, then I may bore it out, and install new seats and valves.

  13. #13
    Registered User tanker4me's Avatar
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    From my own experience on a '92GS, '72/5, & '76/6 I was surprised at first that there was oil present in the tube.

    In all 3 bikes the valve was working as designed. As stated before there will be some blow by even in normal operation.

    Two things that I have learned with these bikes that cause oil consumption to vary.

    Kurts reply X1.
    1. I noticed when the oil was kept "topped off" oil was consumed at a rapid rate until the oil was at about halfway between the high and low marks on the dip stick.

    2. When riding my first Airhead, while on the road I kept the rpm around 4000 or 4500. The local mechanic said he decarbonized the heads and pistons when he did a top end reseal at 30,000 miles. The question I asked him was, what could be causing the carbon buildup? I thought that the cause might be crappy gas or incorrect tuning.

    He asked what rpm I ran at.
    Then he said to run at 5000 rpm.

    I've noticed a small increase in oil consumption at 5200+ rpm but the bikes run in a sweet spot around 5000 rpm.

    Bill
    Last edited by tanker4me; 10-26-2018 at 11:35 PM.
    We are all here for a spell, get all the good laughs you can.
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  14. #14

    OIl Consumption

    Quote Originally Posted by tanker4me View Post
    From my own experience on both a '92GS & '76R90/6 I was surprised at first hat there was oil present in the tube.

    In both cases the valve was working as designed. As stated before there will be some blow by even in normal operation.

    Two things that I have learned with my bikes that cause oil consumption to vary.

    Kurts reply X1.
    1. I noticed when the oil was kept "topped off" oil was consumed until the oil was at about halfway between the high and low marks on the dip stick.

    2. While riding my first Airhead, I kept the rpm at 4000 or 4500. The local mechanic said he decarbonized the heads and pistons while doing a top end reseal at 30,000 miles. The question I asked was what could be causing the carbon buildup expecting that it was crappy gas or incorrect jetting.

    He asked what rpm I ran at.
    Then he said to run at 5000 rpm.

    I've noticed a small increase in oil consumption at 5000+ rpm but both bikes run in a sweet spot at 5000 rpm.

    Bill
    I learned at my first Reg Pridmore Trackday (CLASS) that RPM's are your friend.

    RickR90s

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