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Tecumseh TVS 600 2-stroke kickback - not flywheel key

Discussion in 'Mechanic and Repair' started by landspeed, Feb 12, 2010.

  1. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,249

    Good catch, Fixdiss. It has been such a long time since I have seen an old Tecumseh 2 stroke that I had forgotten that the engine was equipped with the flywheel bushing key and I didn't even bother to check the parts diagram. This was typical of the Tecumseh 2 strokers on older single stage snow blowers. Only problem is I don't remember the configuration of the indentions to align the flywheel and crank. Certainly another option to consider.


    FIXDISS LawnSite Senior Member
    Messages: 445

    The one I have is in good shape and is stamped "01".This one is on an old post-hole auger. I acquired 2 of those a few years ago in some surplus equipment and I just couldn't let this one whip me.
  3. landspeed

    landspeed LawnSite Member
    Messages: 7

    Fixdiss - on my mower, it has the same kind of flywheel key - it is actually more like an almost complete tube, with a lump on the inside, which fits into the notch in the crankshaft, and a lump on the outside, which fits into the notch on the flywheel. The two notches are 90 degrees apart, apparently an 'index flywheel key'. The key is in good nick (a little tiny bit worn), and, if I have the flywheel on without the nut in place at the top, the flywheel won't move freely (the key does lock it into place on the crankshaft).

    If I could get a different key which isn't offset by 90 degrees, it would actually solve my problem! Except for the fact that I still wouldn't know why the timing went out by 90 degrees in the first place?

    I think it must be the crankshaft, becoming bent in some way, but it has become twisted by exactly 90 degrees, while still remaining 'true' with absolutely no bend, so that the piston is still at TDC and BDC as it should be, just 90 degrees out, and there is no resistance at all when the sparkplug is removed (suggesting no sideways bending of the crankshaft). I didn't even think it was possible to twist a crankshaft 90 degrees like this - but I can't think of any other explanation - so that must be what has happened!

    Currently thinking of getting a decent 4-stroke Honda mower, and will likely pull the Tecumseh apart in a weeks time if I can't figure out what has gone wrong, to see if I can fix it!

    Unless anyone else has any ideas as to what might be wrong?

    Thanks for your help so far :) Learnt a lot about 2 stroke engines, even if I can't fix this one yet!

    FIXDISS LawnSite Senior Member
    Messages: 445

    Ok, I just checked this one I have again. When the piston is at top dead center,the key-way in crankshaft is over 1/4 round past the center of the ignition coil and when flywheel is slipped on with key properly in place the magnet on the flywheel is past the center of the coil to the point that the Center of the coil and the 1st fin on flywheel are lined up. Where does yours line up in relation to TDC ? Also check and see if there is a # stamped into the key/bushing . Mine is stamped "01" and the part # for mine and yours are not the same according to the parts illustrations I have checked.
    Last edited: Feb 14, 2010

    FIXDISS LawnSite Senior Member
    Messages: 445

    Before you tear into it try replacing the shear-key/bushing. I still believe that to be the problem rather than the crankshaft.
  6. VegetiveSteam

    VegetiveSteam LawnSite Senior Member
    Messages: 296

    Is the blade now in fact tight??? Anyone who has ever tried to start a lawn mower with a loose or with no blade on it can tell you they thought they might have lost some fingers when they tried to start the engine. With a loose or with no blade they kick back quite violently and will rip the starter handle right out of your hand.

    Now with all that being said, the key/adapter even with slight damage can cause similar problems. Also what color is the key/adapter? If it's a gold color your have solid state ignition. If it's just a plain silver or gray color it is more than likely a point ignition.
    Last edited: Feb 15, 2010

    FIXDISS LawnSite Senior Member
    Messages: 445

    Landspeed,did you ever get a new flywheel bushing to see if that corrected your timing problem ?

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