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Thread: Crankcase Breather

  1. #1
    Living the Legend Bigrider's Avatar
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    Crankcase Breather

    I've read in several articles that the old style crankcase breather valve (R90/6)can be (should be) replaced with the newer style reed valve. I have not read anywhere how this is done. I can see where would have to remove the post (it's pressed in), but since the new reed valve sits higher, will the cover have to be replaced also, or does the three hole orifice pop out someway and the reed valve sits in the old location. Thanks

    Dave H
    Colorado Springs, Co

  2. #2
    Administrator 20774's Avatar
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    I don't know about "should be". Unless there's some reason to believe the current breather is sticking open, letting oil mist by, or generally making a turkey gobbler sound, it could be left alone.

    However, there should be a housing over the breather valve. If I'm not mistaken, the vertical profile of the new reed type is actually lower...there's no middle post sticking up. Once you pull the old valve out (I used a make shift slide hammer affair), the new one just presses into the same place as the old valve. Be careful in orientation of the opening of the reed valve and/or the screw that holds the fixed end to the base. On my /7, I had to put the screw in the 5 o'clock position or nearest to the right footpeg. Otherwise, there was going to be clearance issues with the cover.

    HTH...Kurt in S.A.

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    breather valve

    I'ts been over 10 years years since I changed out the old breather to the "newer" design. I believe I heated the area around the post with a heat gun, then pulled the post with a homemade puller. I can't remember having any problems.

  4. #4
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    The post was no problem, it popped out with a pull of the pliers. The original valve disk is about 1/32 thick. The reed valve is probably around 1/4 in thick. Although the new valve "fits" in the old location (same diameter), the housing cover does not fit flush over the new valve. Sounds like a need for a new cover.

    Dave H
    Colorado Springs, Co

  5. #5
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    When I removed my old breather, it was not only the post but an entire assembly. The center post was connected to a round flange via three spokes...it's difficult to describe and I'm trying to remember things. The disc was connected to the post and was held down to the top of the case/flange with a spring. I first removed the circlip so the spring could be released and then the disc could be slid off. I then used the slide hammer to remove the remainder of the and a big hole was left. The new breather just tapped down into the hole and ended up being essentially flush with the top of the case. The old cover fit just fine. Maybe things are different on a /6...but the parts CD seems to show basically what I'm talking about. There should be nothing left in the hole once you pull out the old breather. Do I have that all wrong??

    Kurt in S.A.

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    breather

    Kurt, I couldn't have writen that any better than u just did. I think u covered the subject quite well. The parts microfiche shows this on p.11/5 & 11/18.

  7. #7
    Registered User donbmw's Avatar
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    I changed mine on my 75 R90/6 to the newer type, the new type reduce the amount of oil that would come out. Did not have to change cover.

    Don

  8. #8
    Living the Legend Bigrider's Avatar
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    Quote Originally Posted by 20774
    ... The center post was connected to a round flange via three spokes... I then used the slide hammer to remove the remainder of the and a big hole was left. The new breather just tapped down into the hole and ended up being essentially flush with the top of the case. The old cover fit just fine....
    Kurt in S.A.
    We are talking the same thing. There is a three hole item (plug) that the post sits in. My question was does this three hole plug come out to facilitate the new reed valve. From your discription, it does. I just need pull the three hole plug out. Thanks

    Dave H
    Colorado Springs, Co

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    breather valve

    The reed valve sets on it's on round aluminum housing(plug) . The part # 11 11 1 335 712 shows that being 3 parts. The round aluminum housing, the reed valve, and the screw to hold the reed. So the old housing comes out and the new one is pressed in. The reed is screwed down to the new housing and the breather housing cover is bolted down over that. Hope that helps. Go to one of those dealers that have the parts fiche on the net and look at those pages I gave in a previous post. That might make it clearer.

  10. #10
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    [QUOTE=barryg]The reed valve sets on it's on round aluminum housing(plug) . The part # 11 11 1 335 712 shows that being 3 parts. The round aluminum housing, the reed valve, and the screw to hold the reed. So the old housing comes out and the new one is pressed in. [QUOTE]

    The part we are talking about is the three part piece you refer to. My problem was that I didn't know you could take out the old three hole plug to fit the new reed valve assembly. I'm not messing with the reed valve, it came as an assembled piece. Thanks

    Dave H

  11. #11
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    Suggestion...put the new breather in the freezer for a few hours before you press it into the top of the case. It should make the job go a little easier and minimize any damage. Both items are aluminum IIRC. Just make sure you tap in the new breather fairly square.

    Kurt in S.A.

  12. #12
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    Success

    The old plug popped out rather easily (with light use of the hammer slide) and the new reed valve tapped in just as easily. Mission complete. I wish I had known about the old plug removal procedure earlier, didn't have to remove and ruin the post. Thanks to all for your advice.

    Dave H

    Coloradoo Springs, Co

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    Thank you all - info and advice helped a lot.

    I read I shud replace the old breather valve with the new reed type. Didn't have a clue until I read the forum threads.

    I just rented a dent remover slide hammer - $10 per day. And then I went to Home Depot to buy a J-hook bolt, 1/4 inch and 20 coarse threads. This screwed onto the end of the removable nut which then screwed onto the end of the slide hammer. Old valve popped out just like everyone said. Also froze the new reed valve and it just tapped right in.

    Ok - now one thought. Last year my right side exhaust valve burned up. My left side exhause valve was ok. I replaced both anyway.

    However, on replacing the breather valve, I noticed its feeder tube fed into the right cylinder and only the right cylinder.

    Is it possible that the right side burned hotter because the fuel mixture had some oil in it from/via the old crankcase breather valve?? I was wondering where and why I used about a pint of oil every 1000 miles.

    Hope the new reed valve answers the question.

  14. #14
    Administrator 20774's Avatar
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    Quote Originally Posted by topoutat76 View Post
    Is it possible that the right side burned hotter because the fuel mixture had some oil in it from/via the old crankcase breather valve?? I was wondering where and why I used about a pint of oil every 1000 miles.
    I doubt it...until I believe 1981, they ran the breather output to the right carb only. With hundreds, possibly thousands of bikes of the '70s still on the road with that setup, there must be other reasons why you had a right side problem and all the others didn't...or haven't reported it.

    Actually, a pint every 1000 miles is not too awful. Are you filling the oil to the very top mark on the dipstick each time you find the level down? Lots of anecdotal information that says you should fill to around 1/2 on the dipstick...less oil volume, more air volume, less foaming and thus less oil mist. Also, some oils tend to burn off their additive package quicker than others. Use a quality oil and this tendency might reduce.

    Have you done a compression test or leakdown test either before or after the valve replacement? You may have excessive blowby on the rings, increasing the crankcase pressure thus resulting in more oil being pushed out.

    What year bike do you have? There was a run of bikes (my /7 has it) where the oil mist that comes out of the breather is funneled forward and down into a cavity in the block. Just forward of the breather is a depression which has a small hole in the bottom of it. This cavity/hole was designed to allow the oil mist to settle and condense out, dripping back into the crankcase. If this hole is plugged on your bike, this could be a source of excess oil to the right carb.

    I would look for other things to have cause the right valve to burn up. Probably carburation, valve settings...maybe just luck of the draw - the left side of the bike was built on Monday and the right side was built on the previous Friday??
    Kurt -- Forum Administrator ---> 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!

  15. #15
    Bill Burke
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    Gentlemen-
    A bit late, but James Klossner prepared an excellent photo essay on the subject. Read the commentary, then click on pictures to enlarge.

    http://tinyurl.com/5c94su

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