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2T Engine Siezed on LH Cylinder

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  • 2T Engine Siezed on LH Cylinder

    Happy New Year to all!

    My 2T has seized, & fortunately freed itself after cooling. I was doing around

    50 MPH & the motor has never seemed "tight" as though running in.

    I have removed the top end & the motor has clearly been re-furbished.

    The LH cylinder has been running considerably hotter, (for example the inlet

    manifold gasket was baked to the metal on that side) The piston has taken

    the brunt of the seizure, & I have had the cylinder professionally honed as a

    precaution, & the bore is perfect. The clearance between the skirt of the new

    piston & bore is .0035". I have been using a 20:1 oil petrol mix. (semi

    synthetic)

    I have not as yet checked the timing or points gap, as I guess this could

    cause the above situation ? (I will do that today).

    The members on the forum have far greater knowledge than I, Is there an

    inherent issue specific to the 2T engine? I was running low on fuel could this

    have a bearing on the situation?

    Is it best to use mineral oil as that would be the original specification?

    I will need to ride as though running in, (I assume) what is the best advice

    for this?

    Your input, guidance & comments would be greatly valued!

    Best Regards Bob

  • #2
    2t engine siezed

    check your ring clearance? mine has other issues but seems happy on 32:1 the book recommends 20:1 run in and 25:1 ?

    Comment


    • #3
      Hi Bob. Sorry to here of your seizure (the bike not you)
      The 2T has always been prone to seizure but mainly when new or after a rebore.
      You say the engine looks as though it has recently been refurbished so presumably its had a re bore. I think piston clearance is a bit tight & needs to be .005" So this looks like the problem. Just needs running in a bit more, I would suggest at least 500 miles & preferably with frequent stops to let the motor cool down. I dont know why one cylinder would be running weak, but this may just be overheating due to the 'tightness' of the piston in bore. You could check the ignition timing as this may have some bearing on the matter. As for oil semi synthetic should be OK & at 20:1 is as Villiers recommend.

      Comment


      • #4
        Originally posted by mikerwt View Post
        check your ring clearance? mine has other issues but seems happy on 32:1 the book recommends 20:1 run in and 25:1 ?
        Thanks for your advice.

        Cheers Bob

        Comment


        • #5
          Originally posted by John Wakefield View Post
          Hi Bob. Sorry to here of your seizure (the bike not you)
          The 2T has always been prone to seizure but mainly when new or after a rebore.
          You say the engine looks as though it has recently been refurbished so presumably its had a re bore. I think piston clearance is a bit tight & needs to be .005" So this looks like the problem. Just needs running in a bit more, I would suggest at least 500 miles & preferably with frequent stops to let the motor cool down. I dont know why one cylinder would be running weak, but this may just be overheating due to the 'tightness' of the piston in bore. You could check the ignition timing as this may have some bearing on the matter. As for oil semi synthetic should be OK & at 20:1 is as Villiers recommend.
          John, Thanks for your advice.

          Cheers Bob

          Comment

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