Main bearings

Of all the parts used in a parallel twin, these are on the top of the list of hard to find items. Not a single bearing distributor nor manufacturer has these bearings in their standard supply, so the best (economical) decision is to make them yourself.

The design has been slightly adjusted with more lubrication groves in the flange to accommodate the axial load of the crank, and the groove in the inner diameter is now whole as compared to the original. The first test samples were made of Aluminium bronze, which was used as bearing material in heavy gas powered combustion engines for the crankshaft and camshaft and rocker arms, hens the first reason for selecting them.
The did not pass the test, as the crank locked up twice on the dyno once above 4000rpm. The cause was found to be the wrong material, and this was supported by literature on bearing designs and backed by experience from several engine tuners.


So with more information I set out to find more suitable material and have at this moment put out quotations. While the test specimens are made, a separate engine will be put together with these new bearings and bolted into leftover GTV frame for dyno endurance testing.

2 thoughts on “Main bearings

  1. Hello Andre,

    I would like to contact you to ask you for a small help. I need to
    advise about Ducati 350 GTL engine repaire. The engine got stucked during
    race and it is needed to replace main bushings of crankshaft.
    Unfortunately original spare parts are not available on our market in CZ.
    Is that common also for your market?
    How do you solve such a issue? Do you produce the bushings completely new
    or just provide new surface treatment of existing ones?

    I am looking for your feedback. Thank you very much in advace.

    Best Regards,

    • Hi Vitek,
      Same issue here in NL: no main bearings available.
      I am in the process of engineering new main bearings but need to test them aswell, so i am making a test engine for these new bearings for dyno endurance. The only thing is it will take some time for sourcing the correct material.

      I might have some used (but in good condition) main bearings, and a 350 GTV crankshaft if you are interested? You can contact me for further details at
      Regards, Arthur

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