engine won't crank manually

Discussion in 'Mechanics Garage' started by lnb001, Mar 29, 2010.

  1. lnb001

    lnb001 New Member

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    I have a 1984 VF750 that I have slowly been working on. This past weekend I finally dropped the engine from the frame. I want to assess the integrity of the engine and try to do some compression testing. I have tried cranking the engine via the rotor bolt but it won't budge. I've tried clockwise and counter clockwise. Is this a bad sign? Does the transmission need to be in neutral for this? Sorry if these are stupid questions but I figure this is the best place to ask.
     
  2. squirrelman

    squirrelman Member

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    Pour some oil and kerosine down the sparkplug holes, let it sit a few days, and try again.

    Your engine is frozen up, most likely piston rings rusted in place, but it could also be a damaged transmission.

    Engine should turn easily in either direction.

    Good reason to ALWAYS verify that the engine will turn by hand or by pushing b4 any purchase.

    Grab something off CL if you want to ride this year.
     
  3. GreyVF750F

    GreyVF750F Member

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    yes put the trans in neutral. then try again. If nothing do what squirrel says with the oil. use WD40 or some penetrant type.
     
  4. donald branscom

    donald branscom New Member

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    You should not turn the engine over backwards. A little bit is ok, but you can get the cam chain to jump a tooth if you turn it backwards too much. Also if you try to turn the engine backwards it could loosen the rotor bolt. The tensioners are not made to run the chain backwards.
    If you remove the spark plugs it will be much easier to turn over.
    Put the engine in neutral. just use the shift lever and turn the counter shaft sprocket by hand if you have to to get it to shift.
    Sometimes the shift dogs wont line up with the holes and you can bend a shifting fork if you try to force it in or out of gear without the clutch. That is why you might have to rotate the countershaft sprocket a little.
    It would have been better to put it in neutral before removing the engine.

    Do not force the engine to turn over if it has a known defect, because you could bend a valve if the timing is out.

    You should have done the compression test BEFORE removing the engine. Now it will take two people.
    To do a compression test the engine must rotate at a fast enough rate and the throttles must be open.
    One person to hold the engine and one person to use the compression guage. and you will have to use and automotive style remote start button switch tool.
    To do all that you will need to hook up a good battery.
     
  5. lnb001

    lnb001 New Member

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  6. Jakobi

    Jakobi New Member

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    Yes.

    -Jake
     
  7. dino71

    dino71 New Member

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    How the heck are you going to do a compression test with the engine out of the frame of the bike??? Correct me if I am wrong but doesnt the engine have to be at temp (160-175 f) in order to do a compression test? The rational is that the piston/valves/cams etc etc have expanded from the heat and the clearances have closed up a little therefore giving you the best compression.
     
  8. Jakobi

    Jakobi New Member

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    I've done compression tests on cold motors. If things are seriously out of whack it will show up. Do expect lower numbers than what you would normally see.

    -Jake
     
  9. donald branscom

    donald branscom New Member

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    Last edited: Mar 29, 2010
  10. donald branscom

    donald branscom New Member

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    NO..... the engine can be stone cold. It doesn't care. Will make almost no difference.
    The throttles have to be open, the battery has to be fully charged up. All spark plugs out.
    NOTE: Some engines and some books require that the plugs stay in, but in actual practice there is not much difference and with the plugs in it just wears the battery down faster.

    "Valves expand from heat" Well that might be able to be measured but the compression would be the same .
    Of coarse a valve adjustment and prior slack taken out of the cam chain (cam chain tensioner adjustment) will make a difference. But not that much. I would just do the compression test and see if there is a major defect. Because if one cylinder only has 40 lbs compression then you are going to have to take it apart anyway, so why go through a valve adjustment and cam chain adjustment to start with. Do it after you find out if things are reasonable.
     
  11. lnb001

    lnb001 New Member

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    Wow thanks for the great info. I will try this out this weekend, assuming I can find a relatively inexpensive battery.
     
  12. donald branscom

    donald branscom New Member

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    Just use any car batttery.

    Hook the ground of the car battery to the motorcycle engine block and hook the remote start button between the positive of the car battery and the stud sticking out of the motorcycle engine starter. Make sure no flammables are in the vicinity in case there is a little spark. Sorry I had to throw that little disclaimer in there.

    Make sure to put a NUT on the starter terminal of the motorcycle so the threads do not get zapped. That could cause trouble getting a nut on the threads later on.

    You can just use a set of car jumper cables and use your remote start button from the positive jumper cable from the jumper cable to the stud on the motorcycle engine starter terminal. Make it easy on your wallet.
     
  13. captb

    captb New Member

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    Since the engines out I would pull the valve covers and see if the chains look tight (loose is bad) then you can look and make sure all valve springs and keepers are ok, if you get it to turn over you can verify cam timing, then check/set valve clearance, easier with the engine out.
     
  14. squirrelman

    squirrelman Member

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    IF u can't spin the motor by hand with a socket and breaker bar, there's NO WAY the starter motor will turn it over......no matter how big the battery. Don't even try.

    Anyway, there's NO NEED for starter switch......just touch +12 volt to starter terminal, but it's hopeless unless you can turn it by hand.
     
  15. lnb001

    lnb001 New Member

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    Im thinking, like you said, that the piston rings are rusted in place. Last summer I was able to manually rotate it, so maybe like you suggested after some kerosene and oil it will free up after a couple of days. If not, guess I am screwed.
     
  16. TOE CUTTER

    TOE CUTTER Mullet Man

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    Do not try to turn it over and disassemble and inspect. If rusted, run a hone through it, I have been suprised many times how superficial the the damage is. Good luck.
     
  17. squirrelman

    squirrelman Member

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    IF you turned it b4, chances are favorable..... PB blaster may have more penetrating power....but who really knows??
     
  18. mrich12000

    mrich12000 New Member

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    Take the heads off. go from there .Just like Toe said.
     
  19. squirrelman

    squirrelman Member

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    Heads off wont help much if rings are rusted or trans is locked up.
     
  20. mrich12000

    mrich12000 New Member

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    Go with heads off split the cases.!!
     
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