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Sherpa T / Alpina Motor How Interchangeable?


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Hey everyone. Brand new here and picked up my first Bultaco. It runs and is about 75% original, however knowing this is a trial forum, I am looking to go the other way. I would like to change the gearing some to make it more of a "desert sled", less low-geared trials. I know the 71 Alpina is basically the same bike with higher gearing. Can anyone tell me how interchangeable the gearbox is?

Any input would be appreciated.


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The gearbox from an M85 Alpina should go straight in but later models will have differences in shaft diameter and clutch hub mounting so aren't a straight swap

Much easier to just change the sprockets than gearbox ratios. Standard Sherpa size for that year is 11 / 46 for a 520 chain or 13 / 52 for a 428 chain, just fit bigger front, smaller rear

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You don’t say what model of Bultaco you have. This is key. I have an M98 Alpina that I turned into a trials bike for vintage trials. I used the trans gears and heavier primary flywheel from an M91 Sherpa T to compliment all the other modifications.


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