TS 125 gearbox

Forums Technical Two Stroke: Help needed TS 125 gearbox

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    • #5023

      Now rebuilding my motor with new seals, bearings, big end & a rebore. Having carefully vernier / feeler set the various gear to gear gaps according to the OEM / Haynes manuals I find that there is no gear change operation after replacing the RH crankcase. The change sort of worked when loaded into the LH casing – I expected it would improve with the proper shaft alignment & support when the other casing fitted.

      I was careful to ensure the gears & shafts went back in as they’d come out (as bike a non-runner when bought it’s possible there was something wrong before). The arrangement checked out with the various pics & drawings in the manuals.

      There are no damaged teeth or shaft wear I can see and the shift mechanism all appears to be in good condition.

      If I tip the motor one way I can get the primary shaft to rotate by hand & the gearbox output shaft to move at the same speed.
      If I tip in the opposite direction I can hear a gear slide to a different position, which then locks the gearbox up, with neither shaft able to rotate. This doesn’t feel right – a floating gear able to move along its shaft according to the orientation of the engine!?

      Any gearbox gurus out there that can give me a steer on this? – clearly no point in progressing the motor build any further until this is fixed.

      Many thank for any suggestions or comments.

    • #5034
      A A A Dummy

      Sounds like the selector has slipped off the geartrain its a funny thing that moves both top centr gears and bottom centre gears (2nd and 3rd gear only) you can suss it out with all the gears in the left case
      The neat thing is that each gear selects in turn along the shaft from left to right
      After the cases are together in top gear I adjust the selector rod (directly below the clucth) screwing clockwise until third and fourth are just touching then back off about 1/4 turn the gears should work ok then
      Remember the clutch centre locknut should be tightened as it holds the top shaft in position
      Hope this helps

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