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Thread: Air-noise

  1. #1
    Rally Rat MAGWA's Avatar
    Join Date
    Mar 2003
    Coarsegold, CA


    In response being informed about a Tech Day next month, I sent the following to Darryl. He responded with some suggestions.

    Since then, I've noticed a little more oil-seep at the bottom of the alternator cover.

    Anybody want to chime in? Thanks.

    "I NEED that tech day!!!

    R100 is *looking* good. Have ridden her about three tanks full since
    the reclamation. Heard some noise from what I think/thought was the
    left head /barrel area.

    Kind of like pinging ...butt in baritone. I thought: "I had the
    heads and barrels off (pulled the wrist pins and left the
    pistons/rings in the bore) to put on new pushrod seals. Maybe I have
    a loose rocker arm bolt?"

    Spun around back home and, as long as I had to ride the bike to get
    back to the garage, decided to diagnose. The noise audibly comes on
    under load at about 4-4.5k. Never in first or second, as much as I
    could tell. At first, that made me think it was a body-part rattle
    telegraphing out to pretend it is a motor part. Bugger.

    Just riding on the flat at 3k and twisting the throttle will get
    discernable noise, even with the helmet closed. About 4k and up.
    Running through 1st gear to 5k and over I don't hear it. I have ****ty
    ears, though.

    Home...on the floor. Check every body part known to man. Get out the
    exhaust wrench. Tight as a drum. Wait for the bike to cool down.
    With for *me* to cool down. Go for a ride on the R1150RS around Bass
    Lake and down to Northfork...with Fronch.

    Back home on the garage floor. Off come the rocker box covers.
    Out with the plugs. Right plug is a little gray. Left is cocoa
    brown. Never did balance the carbs. It ran to well to worry about it.
    Until now . Gotta get the lean out of the right one.....not related,
    I'm sure. Wrong side, wrong issue, wrong manifestations.......

    Re-torqued the rocker arm bolts to about 26ftlb. They were all even,
    butt a little loos. I guess they had "grown a little" in the 300-400
    miles or so. Valve clearances had shrunk I result, I guess.
    I re-clearanced the valves to 10I- 8E.

    Uh oh! A little "seep" on to the front crossover pipe. From under my
    nice, shiny polished alt. cover. Related? Cam chain? The bike has a
    pretty soft 33k on it. I don't know.

    Rode off. Seemed smooth. No noise. Still, I was not riding not
    under load....neighborhood stuff, you know. Kids, etc. Turned north
    on 41. You might remember it goes up hill to a two lane passing area.
    Bike performed well butt back was the noise. No falter in least *on throttle*.

    Rode into Coarsegold a couple of more miles and turned around.
    Backfire on deceleration, It has done that from the start. But not
    as much. I have a couple of small exhaust leaks where the tangs in the
    crossovers have broken off. I had the header and cross-over pipes
    ceramic coated with aluminum impregnation. Pain in the ass.

    Anyway, rough running (nominally) at slow speeds and stalled at the
    new light turning back on the 417. No wonder, since the carbs need
    attention. Certainly more than likely to be the cause of the rough
    idle and low speed "bucking", too. Started right up. Earlier today I
    turned the idle down to try to get rid of a slow return to idle when
    warm....also I believe to be "another story".

    Back at the garage, I saw no more alt cover oil seep. Butt I didn't
    get down on the floor. Also I'm remembering that when I changed out
    that diode board to the Thunderchild, there was some discoloration up
    high that may have come from that breather that is up there. You
    know, the one that helps make changing a diode board so fun?

    I'm thinking my next bet is to pull the jug again...on the left make sure that the wrist pin keeper(s) are seated and that
    I don't have a wrist pin end carving a new vertical oil groove in the

    Any thoughts? Any of your Airhead Bros that might be interested in
    taking a cyber-shot at it. Or suggesting an approach? If it is,
    indeed, the cam does one know that? Do I pull down the
    left side of the motor before I dig into that diagnosis?

    I could use some help."
    Attached Images Attached Images

  2. #2
    Well, magwa, on my bikes, rough running at slow speeds, and stalling at lights is an indication that I have the twin curse of valves out of adjustment AND the point cam rider worn enough to change the timing and reduce the point gap. Maybe your bike doesn't have points. I've never owned an airhead newer than a /6. For me, hard to start is points and rough at idle is valves.

    Backfiring on deceleration is un-burned fuel/air reaching the exhaust. Running rich on one side(spark plug color)would allow sufficient un-burned fuel to reach the exhaust system to back-fire, but so would secondary ignition deficiencies(plugs-wires-coils). These can also result in rigth/left variances.

    I run my valves at .06in/intake and .08in/exhaust cold. Achieving a stable valve adjustment would be a good first step.

    A wrist pin rubbing in a bore would manifest in a serious and rapid loss of performance. The ugly grooves would cause a significant loss of compression in almost no time at all. If you are even a little concerned, lift the cylinder to make sure.

    Something come loose inside the motor would be noisy all the time, so I think your trouble is a combination of fuel/air, secondary ignition electrics, and maybe primary ignition electrics. Make certain that your timing is not significantly advanced at idle.
    Good luck, JAS
    Last edited by woodnsteel; 03-21-2005 at 04:34 AM.

  3. #3
    Rally Rat bprigge's Avatar
    Join Date
    Nov 2004
    North Branch Minnesota


    I would get real serious about exhaust leaks before I pulled the motor apart
    again. Exhaust leaks are the most noticeable under heavy load. My Clymer
    airhead book says to change the compression rings that go under the exhaust nut if you have any leaking up there after a tear down. Bruce

  4. #4
    Rally Rat tvrla's Avatar
    Join Date
    Oct 2004
    Portland, Oregon

    First off, it would help knowing what bike you've got. And what's been done to it. It looks like an 81 - 84 model. Right? That means it's got electronic ignition. But it may be a 79 or 80, in which case it's got the points in a can. A great system, but you'd have the points to check. They don't wear very quickly, but it's something else to check.

    What it sounds like to me is carb adjust and synch. And, regular tune up stuff. Don't start thinking it's a major internal problem when it's running fairly well most of the time.

    Also, these bikes shouldn't be worked hard below 3500 rpm. It's something about boxer motors - just like Porsches and VWs. It's very hard on them to be lugged.

    This could all be due to a tuning issue and then pushing it at lower RPMs. Do you need help tuning the carbs?

  5. #5

    Unhappy Oil seepage

    I also experienced oil seepage from around the alternator cover. Trouble was a leaky master cyclinder.

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