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Thread: Rattle under hard acceleration R1100RS

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    Registered User skotlyc's Avatar
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    Rattle under hard acceleration R1100RS

    Hello all, Quick question... Under VERY hard acceleration, I hear a rattling noise for about a second or so and then it goes away. The sound is more of a tinny clanking sound like someone put a few bolts in an aluminum can. Its very hard to tell where the noise is coming from because I'm doing about 80 when I hear the noise. I have to duck down below my windscreen to hear it too. It doesnt seem to be RPM specific although the most vibration under hard acceleration occurs around 3500 to 4000 RPM. Its not a consistent rattle, for a while I thought it was vibration causing my center stand to clank on the exhaust, but I disproved that theory. No metal in the oil either. I'm wondering if it is fuel related along with carbon deposits inside the engine. Any thoughts?

    Scott

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    Small road corner junkie pffog's Avatar
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    Knock, try premium, even then can still happen
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    Registered User skotlyc's Avatar
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    I have always put 93 octane in, but here in northern Indiana, I wouldn't trust it.

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    Quote Originally Posted by skotlyc View Post
    No metal in the oil either.
    ...yet.

    Just kidding.

    Knock, ping, detonation.
    The R1100 needs 90 octane, and really needs non-ethanol fuel if you can find it.

    I don't know about carbon deposits.

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    Quote Originally Posted by skotlyc View Post
    I have always put 93 octane in, but here in northern Indiana, I wouldn't trust it.
    93 ?!?

    Maybe there's more going on?
    There is a small amount of manual adjustment (3 degrees?) available on the Hall Effect Sensor plate.
    Doesn't seem like enough to make it ping.

    Are you using regulation spark plugs?

  6. #6
    Registered User skotlyc's Avatar
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    honestly haven't checked. Still running the spark plugs that came with it. I think they are just the NGK cheepo's. Maybe champions... dont know. So fuel/spark is the likely cause?

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    Quote Originally Posted by skotlyc View Post
    honestly haven't checked. Still running the spark plugs that came with it. I think they are just the NGK cheepo's. Maybe champions... dont know. So fuel/spark is the likely cause?
    Low octane fuel is the most likely cause of detonation by far.
    This engine doesn't need more than 90 octane. You should have to go to 87 octane to get pinging.
    Since you're running 93 octane...
    Theory rejected.

    Back in the day when we had to adjust it, too much spark advance was the second most likely thing.
    However that is supposed to be pretty tightly controlled on this engine by the all-knowing Motronic.
    Rejected.

    The next thing is anything in the combustion chamber that might collect heat to the point of igniting the mix prematurely.
    That would be carbon deposits, or a "too hot" spark plug.

    I would think the detonation itself would blast the carbon deposits right out of there.
    Rejected.

    That leaves me with the spark plug, and I'm reluctant to put my money on that - the "heat ranges" overlap an awful lot and you almost have to put the engine in race conditions for a sustained time to have a problem with a hot plug. A "hot" plug isn't really that much hotter than a "cool" one.
    By the way I like the Bosch 4417.
    ...Rejected.

    So I reject all theories so far. And the post is already a bit long, very sorry, I like to "show my work".
    Let's go back to your original post...
    It seems like you are associating the pinging with some unusual vibration - am I reading too much into that?

    The other thing that can cause detonation is running way too lean.
    I'm wondering if you need a Throttle Body Synch.
    You see, the amount of fuel that both cylinders get is determined by the Throttle Position Sensor that is on the left throttle shaft.
    If the right throttle is open more than the left throttle then the right side will be running very lean.
    If it runs lean enough it will ping and will also not be producing the same thrust that the left side is, and you get vibration.

    There's a certain technique to the Throttle Body Synch that you may or may not want to tackle, I can dig up some instructional material if you like...

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    Registered User dieselyoda's Avatar
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    Some of them do rattle.................

    Pre-Ignition and detonation are distinctly different. They sound the same though.

    If it was me, I'd start with scott.lambert's suggestion, throttle body sync check, throttle position voltage check. If you have a problem with either before any adjustments, you got a bit of clue.

    For me, if I was already into it, I'd check my my valve adjustment and my rocker shaft end play, before I got all crazy with adjustments.

    Octane, percentage of Ethanol and spark plug heat ranges would be something to look at. Maybe..................

    For me, I got barely 5 months of a riding season. I would probably just drop a gear and keep the engine RPM a little higher. I also might by-pass that extra good beer at the bar that adds a bunch of calories.
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    Registered User skotlyc's Avatar
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    Just synced the TB's about a month ago along with valve clearance check. Thinking seriously about doing the water torture to get rid of any carbon build up before I start adjusting things. Planning to check spark plugs tonight too. Any thoughts on the water torture? Bad, Good?

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    Registered User roger 04 rt's Avatar
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    Here's a recent board on another thread you may want to check out: R1150RT Pinging near 4000 RPM in 5th or 6 th

    You can try the water torture which sometimes work and sometimes doesn't. I heard of, but never seen, bits of carbon get broken loose and stuck between a valve and seat. I've done it myself on cars back in the 60s and 70s. On my first 733i there was a recall involved with carbon build up, the dealer mentioned something about running ground walnut shells through the motor--were they pulling my leg?

    Anyhow, as a quick fix, you might try swapping your yellow coding plug (30-87) for a blue one (30-86-87a) and see if that does anything. It's quick and painless. You don't need a BMW plug if you can make up a jumper wire.


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    Registered User skotlyc's Avatar
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    Hey... thats a great document to have posted... Thank you. I'll try jumpering before I buy the plug.

  12. #12
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    I would also suspect pinging/detonation. My 94RS used to do some pinging way back in 95. I adjusted the HES/timing slightly. I run Autolite 3923 plugs (very durable). I also regularly run Techron through the gas to clean the fuel system and injectors (still original to the bike with 172K on the bike). BMW also sells a more concentrated form of Techron that is very effective to clean up the fuel system. It is a good point to avoid ethanol fuels when possible. But I feel it only matters mostly if the bike is left stored for extended periods. As long as you run the ethanol based fuel through the bike I doubt it is detrimental other than reducing fuel mileage.

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    Quote Originally Posted by skotlyc View Post
    Just synced the TB's about a month ago along with valve clearance check. Thinking seriously about doing the water torture to get rid of any carbon build up before I start adjusting things. Planning to check spark plugs tonight too. Any thoughts on the water torture? Bad, Good?
    I'm afraid of the water torture. I just don't know what it's going to do. I have accidently fed mine the contents of a homemade manometer made with water (almost a cup) and it didn't even missfire. A little steam cloud pooped out, that was it.

    I was going to suggest checking the valve lash but I am not sure if having too much lash will raise the compression ratio or effectively lean the mix, or do anything that might induce a ping or knock.

    I have experimented with reducing the lash and I have read up on experiments increasing the lash (to bump the edges of the powerband around) and have heard no horror stories.

    I know that "too tight" lash will (let's go ahead and say will) increase the overall temperature of the combustion chamber and the exhaust valve in particular. By how much I don't know.

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    MOA #24991 Pauls1150's Avatar
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    I've never actually seen carbon stuck between a valve and seat, but I've seen the damage that follows... not pretty. The carbon may have been sucked out of the smog canister; hard to know fer sure unless you compare granules, or the canister's vacuum line has grit or gas in it.
    If you really suspect carbon buildup, instead of water (internal steam blasting), try a little Marvel Mystery Oil in the gas - this is a VERY high-detergent lube that will dissolve "stuff". And your exhaust will smell minty... Some Sea Foam might help too. Techron is great stuff, but I don't know if it actually cleans out old burnt carbon -?

    If you want to inspect for carbon, you may be able to either shine a flashlight, or snake a LED on a pair of wires, down the sparkplug hole (slowly bump the rear wheel in 5th gear to view the valve margins and the top of the piston); another way would be to pull the intake tube and look down thru the open valve. Down side is that the view is still limited, and if it's on the exhaust side, where carbon is more likely, you can't see that. Pulling the headers can be labor-intensive.

    Re plugs - I've had better luck with the right NGKs than I have with Champions (on several bikes), and for the 1100, Autolite's 3923 is unbeatable. (Yes check the gap before installation.)

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