lightened flywheel

Discussion in 'Airheads' started by chasbmw, Jan 18, 2013.

  1. Kai Ju

    Kai Ju Long timer

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    Except when you're in chasbmw's shoes where you have a modified flywheel that was balanced with the rest of the engine.
    #21
  2. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Yeah, but what's more work; assuming his teeth are actually beyond repair, finding another flywheel with "good" teeth and 1) lightening it or not... or 2) pressing the ring gear off the new one, pressing the ring gear off the old one, and finally pressing the ring gear on the new one and hoping/assuming it's still balanced?
    #22
  3. Kai Ju

    Kai Ju Long timer

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    All good questions, the most important one being whether he has a flywheel or a starter problem.

    Reading some of the comments it seems that the v-notch may actually be normal. If so then I have to agree that the teeth don't look any worse than the ones in the pic I posted.
    Which in turn means that this is a starter/battery problem.
    #23
  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I don't recall ever seeing a flywheel without the angled tooth faces. They have always looked similar to the ones in question.
    #24
  5. Kai Ju

    Kai Ju Long timer

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    Wirespokes, I've had four different flywheels pass though my hands in the past 6 months and none of them had the v-notch type tooth that chasbmw's wheel has.
    Mind you, they were all '77 vintage as far as I know.
    #25
  6. chasbmw

    chasbmw Long timer

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    It's an interesting discussion about the design of the flywheels. Mine is from a 92 tooth early flywheel, did BMW change the design? Did the design of the starter motor gear change at the same time?

    Mind you on my flywheel the V notch looks to be unworn. They main damage on my flywheel is to the front of the teeth, where it looks to have been bashed by the starter.
    #26
  7. disston

    disston ShadeTreeExpert

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    I found almost 25 flywheels on Ebay in a search. There were even more found on Google. Some of these flywheels have the V shaped cut, or V notch. Not all but many of the unlightened 93 tooth flywheels have this. See;

    [​IMG]

    If there is damage from a 9 tooth starter being used on a ring gear designed for an 8 tooth starter the damage will progress as the flywheel spins. It will appear at one edge of the notch in some places, the middle and then the other edge. Now I've never seen this but it makes mathematical sense. I've never seen a ring gear that didn't work. A few stories about this but nobody has ever taken a picture.
    #27
  8. chasbmw

    chasbmw Long timer

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    Dissiton,

    Any chance of that photo without the cobwebs, I can use a file to put back the facets on the lead edge of the tooth.

    Cheers
    #28
  9. chasbmw

    chasbmw Long timer

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    I have cleaned up the ring gear on my flywheel, with a combination of hand file and Dremel.

    It looks much better now, just have to wait until everything is done and we shall see how well the starter works.

    [​IMG]

    [​IMG]

    [​IMG]
    #29
  10. disston

    disston ShadeTreeExpert

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    What do the teeth on the starter look like? Also the part directly under the teeth of the starter is a one way clutch. It should spin freely in one direction only and it should not be cracked. Often when these go bad they are cracked.
    #30
  11. chasbmw

    chasbmw Long timer

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    Starter motor is fine
    #31
  12. igormortis

    igormortis Long timer

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    Did you ever resolve this? I wonder if I may have a similar problem. Just waiting on a new starter to be sure.
    #32
  13. chasbmw

    chasbmw Long timer

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    The cleaning up with Dremel and file seems to have worked and the starter has got quieter and quieter. The bike is 3500 miles into a trip to Greece and the starter gives me no concern, it's not really under much stress as the bike starts in an instant.
    #33
  14. Voltaire

    Voltaire Bored Of The Rings

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    Could you get the later ring gear and have the old one machined off and the later one machined to fit?
    Reason being is my engineer mate did that to a VW flywheel, put the type 1/2 outer of the flywheel on the Type 4 one. In woodworking terms a lap joint. then he welded it.
    My R90s has a flywheel like yours, sure makes a difference to engine response and gear changing.:D
    #34
  15. Rob Farmer

    Rob Farmer Long timer

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    Why not just fit the later clutch and flywheel? I know you need to fit a later gearbox but the clutch is so much better on the later bikes especially if you're tweaking the engine.
    #35
  16. chasbmw

    chasbmw Long timer

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    I'm finding that a heavily lightened heaven flywheel just hits the sweet spot in terms of smoothness, engine performance and gear change quality! Jim has been known to fit lightened heavey flywheels to the post 81 bikes!

    I did not want to go down the replacement of the ring gear because the flywheel was lightened and balanced with the engine and did not to risk upsetting that.
    #36
  17. Dirt_Boy

    Dirt_Boy Been here awhile

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    Hi Chas, love the swiss cheese flywheel.. I had mine for a R90S lightened back in the day by 750 grams or 1.65 pounds. It should have been more but they told me it takes time to machine the big holes. I noticed that it was smoother under 3,000 revs. :rofl
    #37
  18. chasbmw

    chasbmw Long timer

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    Loved the India pics, brought back interesting memories of the 70s
    #38