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277 A gearbox info?

in 2 Stroke Technical Questions 3 weeks ago
I have a 277 on my ultralight, and am trying to hang the A gearbox.
 
I'm told that they don't need the spacer, but the drive gear on the engine seems to be too long, but I have a spacer that I can use.
 
Looking at the drive gear, the center bolt is not there.
 
Can someone confirm the size of that bolt? The one PDF that I've found referencing it ways that it's a 1/2-20 UNF 50 -- REALLY? An English threading on a German engine?
 
I ran a 13x1.25mm bolt in, and it seems to be the right threading.
 
One way or the other, I have to buy the bolt, but want to get the right one.

  • Re: 277 A gearbox info?

    by » 3 weeks ago

    The correct part  no./size for the Type A crankshaft gear bolt is (No. 841 656)

    1/2-20FX50.  The 1/2: UNF bolt and the 13mm x1.25 thread metric bolts share the same thread

    pitch.

    Hope this helps

     

    Bob R

    Light Engine Service

      
    Report

  • Re: 277 A gearbox info?

    by » 3 weeks ago

    For a bit of explanation on the bolt size.  This engine, the type 277, was originally developed for the SkiDoo snowmobiles made in Canada.  The drive systems, a variable speed belt system, was made by Bombardier in Quebec Canada.  Given this they selected a bolt size that was easy to source in the North American market. 

    Cheers

      
    Report

  • Re: 277 A gearbox info?

    by » 3 days ago

    UPDATE:

    I got a 1/2-20 bolt.  It DOES NOT thread into the hole -- goes in maybe a turn and jams. 

    Now I have to find a 13mm-.25 the right length and try that.  I'm suspecting that it will be the right fit (the one I have is too long, but it threads all the way in and bottoms).

      
    Report
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