Ninja 250 engine rebuild: how do I rotate crankshaft?

Discussion in 'Motorbike Technical Discussion' started by dg1261, Apr 21, 2006.

  1. dg1261

    dg1261 Guest

    I've been tasked with the project of rebuilding the top end on my daughter's
    '91 EL250, which I understand uses the same engine as the Ninja 250. In
    order to get the cams out I need to rotate the crankshaft so the valves are
    closed, but it's not obvious how to go about rotating the crank. Is anyone
    familiar with this engine?

    I assume I'm going to put a wrench on either the left or right end of the
    crankshaft, but I'd like to know what I'm aiming for before I start tearing
    open side cases unnecessarily. It's been 25 yrs since I've rebuilt a
    motorcycle engine, and these engines today have so much junk that has to be
    removed just to get at anything.

    Yes, I did buy the factory service manuals (set of two required)--no Clymers
    or Haynes for this bike, so I had to spend the $75 for the factory manuals.
    Sadly, they're nowhere near the quality of manuals of old. It just says
    stuff like, "turn the crankshaft counterclockwise until the valves...", and
    "turn the crankshaft clockwise 90 degrees...", but no clue as to HOW one
    would turn the crankshaft. It doesn't even give me a clue which side of the
    bike I'm supposed to be on, so who knows which direction "clockwise" and
    "counterclockwise" is!
    dg1261, Apr 21, 2006
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  2. If you really can't find the nut to turn the engine over, and are
    stumped by such a simple task, then I'd suggest that rebuilding the top
    end is way beyond you.

    However, you could always stick the bike in gear and turn the rear
    The Older Gentleman, Apr 21, 2006
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  3. dg1261

    Wudsracer Guest

    Not sure about your bike, but most 4-strokes have a plug in the
    ignition cover that will let you access the end of the crank, where
    you can put a wrench on the flywheel nut to rotate the crank with a
    standard 1/2 drive ratchet handle and socket.

    Jim Cook
    Wudsracer, Apr 21, 2006
  4. dg1261

    NA Guest

    Same procedure for the EX250, Jim described it accurately above...

    In the Service Manual (99924-1066-01), look at photo (right-middle)
    showing the alternator cover on page 8-16 and the photo (right-lower) on
    page 3-7. The plug is in the center of that cover, with the slotted groove.

    The photo (right-top) on page 4-9 shows the timing marks to look for as
    you turn the crankshaft. That inspection 'window' is located between
    the 10 and 11 o'clock position on the alternator cover shown on page
    3-7. It's under a smaller plug with a slotted groove too.
    NA, Apr 21, 2006
  5. dg1261

    NA Guest

    AM EDT:

    The manual specifically states 'counterclockwise' under the Valve
    Clearance Inspection procedure on page 4-15 of the Service Manual. Like
    Mark said earlier, one does need to read through the manual
    cover-to-cover to fully understand the procedures...
    NA, Apr 21, 2006
  6. dg1261

    SAMMM Guest

    if i recall, the left side has a removable cover.

    timing is not particularly tricky.

    make note of bolt lengths on the cam bearing bolts.
    some jerk mixed up these and stripped out a couple of threads
    on the one i fixed up.

    as to when the valves are closed, just look at the cams when you turn
    the crank and observe the cam lobes.
    good luck, sam
    SAMMM, Apr 21, 2006
  7. dg1261

    dg1261 Guest

    Yeah, well my x-ray vision isn't working as well as it used to. You
    conveniently snipped the part of my post where I said, "I assume I'm going
    to put a wrench on either the left or right end of the crankshaft, but I'd
    like to know what I'm aiming for before I start tearing open side cases
    dg1261, Apr 22, 2006
  8. dg1261

    dg1261 Guest

    Thanks, NA, Wudsracer, and SAMMM.

    I do see the plug, but didn't see a description of what it was for. None of
    the old CB750, CL360, KZ400, KZ900, GS750, or GS1000 engines I've rebuild in
    the past had a plug like that.
    dg1261, Apr 22, 2006
  9. dg1261

    dg1261 Guest

    The task I was working on was camshaft removal. On page 4-8, under
    "Camshaft, Rocker Arm Removal", the manual specifically states, "Turn the
    crankshaft clockwise about 90 degrees."
    dg1261, Apr 22, 2006
  10. I rest my case.
    The Older Gentleman, Apr 22, 2006
  11. dg1261

    dg1261 Guest

    Then it's a good thing you didn't become an attorney!
    dg1261, Apr 23, 2006

  12. What did you do after the Comedy Store fired you for being unfunny?
    The Older Gentleman, Apr 23, 2006
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