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Thread: 1974 R90/6 Engine Chirp

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  1. #1
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    1974 R90/6 Engine Chirp

    Hi folks, I?ve got a nice-running 74 R90/6 that makes an engine chirp
    I do not have another airhead to compare this to, but it does not seem normal.
    This bike has done this as long as I have owned it (about 2 years) and only when it is warmed up. When the bike is warm, it chirps, and the sound persists for as long as you ride it.
    The noise is most obvious (easiest to hear) at idle, especially right as you kill the engine. It will do this in gear and in neutral.
    The bike has about 40,000 miles (but not sure if the odo is accurate for actual miles on the bike). Engine has BMW 20/50, and I live in Texas.
    I made a video of the sound this morning. Bike was idling, I revved the engine, then let it idle and killed it.

    Anybody seen something like this?
    Any advice on whether or not to do something about it?
    Thanks so much

  2. #2
    JoeDabbs
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    I have heard in the past that the tube (or the little valve that feeds the tube) that returns oil spray from the crankcase into the right carb can chirp. I have a /6 and it hasn't chirped, but I believe there was a kit you could get for this condition. Otherwise, the bike runs fine, right?
    Joe Dabbs
    2011 RT
    1975 R60/6

  3. #3
    #4869 DennisDarrow's Avatar
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    I have a hard time defining what a "chirp" is; but there is a bird like sound that some have called the turkey gobble. Yes, this is the reed valve that allows the engine to "breathe" vapors from the crankcase/engine and dump it into the right carb. The fix is an upgrade of new reed valve. A pretty simple fix that requires one to pull the tank, remove the starter cover, pull the valve, install the new one correctly (there are a couple of tricks here), and reassemble. You might do a search for this or perhaps Kurt will chime in with his valuable pages and references.......God bless.......Dennis

  4. #4
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    Joe, thanks, and yes, the bike runs great.
    I was wondering if this was something I should address, or if it is just one of those things some airheads will do.
    Any idea on where to find one of these kits? Or if there is a name for the kit?

  5. #5
    Registered User
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    Dennis, I just saw your post and thanks for the good info.
    That sounds like a reasonable fix. I will start some research on the parts and process, and would appreciate anyone other input on getting it done.
    Thanks!
    In the meantime, here is a photo of the bike this morning

  6. #6
    Administrator 20774's Avatar
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    I had a hard time hearing any kind of chirping. If not the engine breather valve, then if the engine is overfull of oil, it will create high internal pressure when the cylinders get to BTDC which can then create problems with seals, such as the rear main seal.
    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!

  7. #7
    JoeDabbs
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    From what I've heard, the sound is just an annoyance...my '75 must have had the newer valve.
    Joe Dabbs
    2011 RT
    1975 R60/6

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