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Thread: #6

  1. #1021
    Join Date
    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Henderson, Waitakere
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    I'm looking at doing the cam timing and need a boss to mount the degree wheel. Ideally I'd like the boss from the middle of the alternator flywheel. I can machine something to do the job but would prefer something with the slot for the woodruff key but don't want to mess around cutting the slot, besides not knowing how to.
    If anybody has a rotor from a late 3LN that they don't want please PM me. Thanks

  2. #1022
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    12th February 2004 - 10:29
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    I have been thinking about how best to determine TDC for doing the cam timing. For fuel and ignition purposes which are fine tuned on the dyno it doesn't matter much. For exact cam timing and repeatability it is critical. The methods I have been using to date have a small error due to the offset gudgeon pins, and in other engines due to offset bores. Any other engineering that means a reciprocating part connects to the rotating assembly by anything not exactly in line with the bore centreline and crank centreline, which must be the same centreline, introduces a difference in degrees of crank rotation for the same piston movement either side of TDC. If a piston stop is used and the crank rotated in each direction until the piston hits the stop, the crank will be in a slightly different rotation position each side, meaning TDC is not exactly in the centre point between the 2 positions where movement is blocked by the stop.
    I came up with the following solution. There is no doubt that the piston is at TDC as there is a screw in the crown pulling it up. The piston can go no further so it is at TDC. As usual with the FZR engine everything is right on the money. I just need a boss to mount my degree wheel and I'll be away.
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  3. #1023
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    12th February 2004 - 10:29
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    One more little step now that I'm back in Auckland. Made a little alloy boss to go on the end of the crankshaft for the degree wheel. One thing I learned talking with Jim is how tapers are dimensioned. It turns out the taper in the rotor is 4mm larger diameter for a 10mm movement along the axis, to within .01mm anyway so it probably is. Some tapers are at various angles but others are a specific diameter increase per axial movement.
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  4. #1024
    Join Date
    25th March 2004 - 17:22
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    RZ496/Street Triple R/GasGas/ etc etc
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    Wellington. . ok the hutt
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    Sorry to hear that. Didn't know that you had made it out. Back by accident I guess.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  5. #1025
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    13th June 2010 - 17:47
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    TDC is TDC regardless of any piston offset. You'll be moving the cams anyway if it doesn't work at whatever figures you start off with.

    What lobe centers do you propose to start with ?

  6. #1026
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    12th February 2004 - 10:29
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    TDC is slightly different dependent on pin offset as the pin is pulling the rod very slightly to the front or back which will result in the crank being rotated very slightly to the front or back. Simple trigonometry will give you actual numbers. I'll zero it up with the piston installed correctly and then again with the piston backwards. It might be a while as I'm busy working on the scooter at the moment to get it all legal.

  7. #1027
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    12th February 2004 - 10:29
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    The only change between the 2 attached photos is that the piston was turned around.
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  8. #1028
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    20th January 2010 - 14:41
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    Quote Originally Posted by speedpro View Post
    The only change between the 2 attached photos is that the piston was turned around.
    Okay but its only an abitrary reference to set to and then alter to what the engine likes.
    besides i would pick the pins prevent them from turning around during running.
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  9. #1029
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    13th June 2010 - 17:47
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    Quote Originally Posted by husaberg View Post
    Okay but its only an abitrary reference to set to and then alter to what the engine likes.
    besides i would pick the pins prevent them from turning around during running.
    The head doesn't care where the crank is when the piston is closest to it. Airflow timing is based around piston movement which can just as easily be measured in distance down the bore. Crank angular measurement is used for convenience.

    i wouldn't count on the pins restricting angular movement. I well remember looking at a hot RGV250 that Grant Ramage had pulled the bottom head off - and seeing the arrow marking the front pointing to the side....And no, it wasn't his proddy one.

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