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Thread: Matt P's Flywheel Issue

  1. #1
    MOA #24991 Pauls1150's Avatar
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    Matt P's Flywheel Issue

    In the November ON, Matt talks about a strange alignment (or lack thereof...) of the timing mark on a '92 R100GS.
    QUESTION: It's been a long time since I've been inside an airhead, so - Is it possible that the factory (or somebody) installed that flywheel "backwards", that is, with the wrong "face" forward? (And then it would be impossible to align its timing marks to TDC.)

    FlywheelSketch.jpg

    And as long as I'm displaying my ignorance... Wes's sketch on page 40 does Not show a "flathead" screw top: that's a "Straight Slot" head. The only way to see that a screw is a flathead would be by rotating the view 90 degrees in any direction.

  2. #2
    Liaison 20774's Avatar
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    Would there be the mounting locations for the clutch on the reverse side of the flywheel? Seems unlikely.
    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!

  3. #3
    Registered User Rinty's Avatar
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    That's an interesting problem he's got. And several Airhead experts have been consulted as well. That's the first time I've seen Matt get stumped by something.

    I've only seen this happen one other time with a BMW; and that was on a K75S that had a mysterious vibration.
    Rinty

  4. #4
    MOA #24991 Pauls1150's Avatar
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    I think the housing cover screws into the pressure plate - not the flywheel.

  5. #5
    Registered User
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    Can't be the flywheel. The bike was running after being tipped over and hydro-locked. It stopped on the way to Matt's house and had to be pushed the rest of the way.
    1980 R100T
    1971 R50/5
    G650GS
    1967 R60/2, 1947 James ML

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    I don't know crap about BMW crankshafts, but I never had seen an engine where you could flip the crank end to end and make it work. Mounting for the flywheel, drive sprocket or gear for the cam drive is always specific.
    Last edited by PoorUB; 11-14-2019 at 03:11 AM.
    From the only real Fargo, ND!

  7. #7
    MOA #24991 Pauls1150's Avatar
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    Yes it was running before the tip-over... but this timing issue was discovered in the course of troubleshooting. It's probably not a "Root Cause", but it certainly demands investigation (which could in turn lead to the cause of the no-start) and correction as long as things are apart.

    Of course the crank cannot be flipped end-for-end; but the flywheel mounting does indeed have FIVE possible solutions, 72 degrees apart each ... and that's before considering if it can be flipped wrong face forward, which, if it can be, makes for ten possible positions. Note that some airheads have been found to have had their wheels incorrectly installed by the factory's assembly line.

    I wonder if anything "different" might then show up on the starting ring's teeth...? Maybe not, if the wheel is symmetrical front-to-back, or its position on the shaft was otherwise altered.

    "Many of us are more capable than some of us, but none of us is as capable as all of us." - Tom Wilson

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    Ahh, I get your drift. I got hung up on Harley lingo where the flywheels are the crankshaft.

    Are the holes equally spaced? Typically when a part like this needs to mount in one position there is a locating pin, or one hole is moved slightly so the part fits in only one position. I would think German engineering would do something to ensure it gets mounted properly.
    From the only real Fargo, ND!

  9. #9
    Quote Originally Posted by PoorUB View Post
    Ahh, I get your drift. I got hung up on Harley lingo where the flywheels are the crankshaft.

    Are the holes equally spaced? Typically when a part like this needs to mount in one position there is a locating pin, or one hole is moved slightly so the part fits in only one position. I would think German engineering would do something to ensure it gets mounted properly.
    Nope. It can be mounted in any of 5 positions.
    Paul Glaves - "Big Bend", Texas U.S.A
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    '99 '03 '06 National Co-Rally Chair Friedle's Avatar
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    Quote Originally Posted by PGlaves View Post
    Nope. It can be mounted in any of 5 positions.
    But only one of those 5 possible positions will show the OT mark in the timing window when piston is at TDC. Both have to happen to be correct. If flywheel is mounted incorrectly, you can paint your own little "f**ked up" dab on the flywheel.

    Friedle
    Ride fast safely

  11. #11
    Quote Originally Posted by Friedle View Post
    But only one of those 5 possible positions will show the OT mark in the timing window when piston is at TDC. Both have to happen to be correct. If flywheel is mounted incorrectly, you can paint your own little "f**ked up" dab on the flywheel.

    Friedle
    Of course. I was attempting to answer the question as to whether it would only mount one way.
    Paul Glaves - "Big Bend", Texas U.S.A
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    '99 '03 '06 National Co-Rally Chair Friedle's Avatar
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    Quote Originally Posted by PGlaves View Post
    Of course. I was attempting to answer the question as to whether it would only mount one way.
    We are saying the same thing Paul....in two different languages. Midwestern and Northeastern.

    Friedle
    Ride fast safely

  13. #13

    Matts problem

    Quote Originally Posted by Friedle View Post
    We are saying the same thing Paul....in two different languages. Midwestern and Northeastern.

    Friedle
    My question: if you set the pistons at TDC and mount the flywheel with the timing mark near the inspection hole in the flywheel cover, how do you get to be out 120 degrees?
    It seems to me you can only be out either 15 degrees or so (i.e. the advance) or you're out 360 degrees because your on the wrong stroke (compression vs. exhaust)? But isn't that a camshaft to crankshaft timing issue?

    It is baffling but I'm with Friedle on this one.

  14. #14
    jimmy armour
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    mats problem

    Hello, I was thinking, the bike ran ok until the crash I believe, then ran almost back to Matts home, then refused to start ,perhaps the exaust has gotten blocked with dirt or bashed enough to block the exaust, this will stop fresh air etc entering the combustion chamber stopping the engine from starting, we did this in Ireland when we were kids stuffing a potato up the muffler of a car it would stop after a few minutes, just a thought looking forward to his return to see what he finds, bye for now Jimmy

  15. #15
    Registered User STEVENRANKIN's Avatar
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    Timing mark alignment

    In the case of the mis aligned timing mark, everyone has to remember, there are people who work on their engines who should not be working on their engines.

    If someone cannot figure out if the engine is at top dead center, or does not take the time to determine if it is, they have no business working on an engine.

    Case in point, my friend's R80RT, the flywheel was installed incorrectly, just as you are talking about. This was done during an oil leak fix. The previous owner changed the oil pump gasket, but did not change the leaking rear main seal. When he put the fly wheel back on, he had it out of alignment and the timing marks did not line up.

    When my friend an I changed the leaking main seal, we put thing to right.

    The people I feel sorry for are the new owners of bikes worked on by careless, incompetent, dishonest people, who find themselves trying to figure out what the heck is going on with their new to them bike. A bike that should be giving them joy not heartbreak.

    Repair guides are not expensive and they are available. Yes, sometimes you need to have two of them because they might just once in awhile conflict with each other or, one may show a slightly different way of doing things but everyone should have one for the year make and model of the bikes they are working on. Even if it is just to do an oil change.

    There are a fair number of people who can in fact do repairs without guides, due to experience or talent, the fact is, most of us do not have this trait. Contrary to belief, it is a good thing for a man to read the directions from time to time. St.

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