BMW R100 blocked ?

Discussion in 'Airheads' started by Nijn02, Jan 6, 2019.

  1. Nijn02

    Nijn02 n00b

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    Hi to all,

    I am rebuilding a BMW R100RS mono of ’88. The build is almost finished. Now I noticed that it is not possible to turn the rear wheel when it is in gear and clutch is engaged when ignition plugs are removed.

    When I try to turn the wheel, I feel some play (assuming that this is the play on the hole rotating part up to the blocking part). At both ends of the play I feel resistance building up. It does not feel like play and then 100% blocking.

    The motorcycle is resting on the engine with rear wheel hanging over the table.

    Diagnose:

    1) Wheel spines free when in Neutral, or in any gear when clutch is disengaged.
    Conclusion: Brakes, rear differential, drive shaft and transmissions are free.

    2) Motor spines free when in Neutral, or in any gear when clutch is disengaged.
    Conclusion: Crank and cam is free, checked chain and alignment, all is correct.

    3) Clutch is working correct to me, removed transmission to inspect, but cannot identify an issue.

    Here is some information about the works done on the engine and transmission. Cylinder head rebuild, new rod tubes, new engine gaskets, new chain + tensioner, new clutch. Rear swing arm has been removed. Rear differential removed and opened it to inspected due to blocking rear brake axle.

    Anyone as an idea, a tip?

    thanks!
    #1
  2. SportsterTom

    SportsterTom Been here awhile

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    Did you remove the flywheel? If so did you block the crankshaft from moving forward while the flywheel was off? There is a crankshaft endplay spacer that can fall off it's pin and then it gets pinched when the flywheel is re-installed. Hopefully that isn't it.
    #2
    FR700 likes this.
  3. Nijn02

    Nijn02 n00b

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    thanks for your input.
    I did not remove the flywheel.
    #3
  4. PaulRS

    PaulRS Dutch fool

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    In what gear are you trying to turn over the engine?
    Put it in 5th and try again.

    If it turns, go down a gear and try again, al the way back to first gear.
    Mind, with every step down a gear, the force required to turn the wheel increases.

    If still no joy, try rotating the engine by the rotor bolt through al the gears.
    Easy, as not to break that bolt.

    Paul.
    #4
  5. Nijn02

    Nijn02 n00b

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    I tried it in 1st or 2nd gear only. at the moment the gearbox is removed and I can spin the engine by hand at the flywheel. no obstructions.
    #5
  6. PaulRS

    PaulRS Dutch fool

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    Ok, so now try the box, spin it via the input and output shaft and go through all the gears.

    But I think your problem is really no problem, just a case of trying things to move in a too low a gear.

    Paul.
    #6
  7. Nijn02

    Nijn02 n00b

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    I think you are correct. all gears seem to work. I will assemble the rear again and test it in higher gears.
    #7
  8. Turtletownman

    Turtletownman Been here awhile

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    When turning an engine over even with plugs removed, you still need to compress the valve springs. Top gear and still need to bump rear wheel.
    #8
    tire joe likes this.
  9. Nijn02

    Nijn02 n00b

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    reassembled the rear and it spins in 5th gear.
    so it was not an issue.
    still happy I removed the gearbox as I forgot to grease the axle that connects the output of the gearbox to the clutch plate.
    thanks for your inputs.

    now I can start to worry about something else like selecting a battery : gel installed bellow the gearbox or Lithium under the saddle...
    #9
    WooPig and aptbldr like this.
  10. Plaka

    Plaka Brevis illi vita est

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    Why would you put a lithium under the saddle?
    #10
  11. Nijn02

    Nijn02 n00b

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    the rear frame is modified and now I have room to put the battery there.
    #11
  12. Plaka

    Plaka Brevis illi vita est

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    do you have a picture of that? I have an 88 and want to put a larger battery in it.
    #12
  13. ME 109

    ME 109 Long timer Supporter

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    Bigger than stock dimensional size?
    #13
  14. Plaka

    Plaka Brevis illi vita est

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    yup. Not interested in Li. I don't think that technology is mature enough yet.
    #14
  15. ME 109

    ME 109 Long timer Supporter

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    Why not a bigger alternator? Unless you're going to make a real cafe bike with a 12 volt espresso machine on it?
    #15
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  16. Plaka

    Plaka Brevis illi vita est

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    first, cash. Big alternator is costly. Second, efficiency. When you USE that big alternator the power has to come from somewhere. I put so many lights on a VW once it would slow down when I turned them all on. The big battery can sip power then drain down when there is a big load. Third, security. Got no kick starter so no battery means no go. Might be warm headed out on the camping trip but frosty the next morning. Lithium no good in the cold. Have to sit around camp with no beer waiing for the battery to warm up enough to start the bike.
    #16
  17. ME 109

    ME 109 Long timer Supporter

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    I don't know where you'd put a bigger battery except on the pillion seat. Maybe a second battery.
    Motobatt MBTX30U is in my bike with heated grips, led head and driving lights. Used to run two 100 watt halogens before the led's. Stock alternator.

    Why don't people use those mini jump start packs for a discreet battery. I don't know if the bike could charge the battery but it would probably start it a few times. If it was in good tune....
    #17
  18. Plaka

    Plaka Brevis illi vita est

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    the '83 has a big battery. 25+ lbs worth. I want one lik tht. The '88 has this limp little thing.
    #18
    ME 109 likes this.
  19. Arktasian

    Arktasian Lets call it Naturalized

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    If you have high draws, then you'll pull more HP off the crank turning a bigger output alternator. Otherwise, apart from mechanical losses its a wash.
    Try the Odyssey PC925, I'm sporting that & just slightly lighter at 23.8lbs (:fpalm). Also have 900watts to charge it.:hide
    Odyssey PC925.jpg

    I'm just trying to model Jeff who carries enough accessories to start a small village at his camp sites
    #19
    ME 109 likes this.
  20. Plaka

    Plaka Brevis illi vita est

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    nice chunky battery. Matter f will it fit in an '88 frame and is it not lithium. I don't have 900 watts but if I wanted them I could carry a generator. I do Have LED lights but if I go off touring again I'll be carryig a small fridge, beats dealing with ice.

    The weight of the alternator rotor is added to the weight of the flywheel. It matters. THEN you lose power to magnetic friction anytime you are drawing power..
    #20