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.
Another trial is converting the crankshaft from plain bearings to ball bearings. This is parallel to the above project to manufacture new plain bearings.
Using the same approach as the Pantah, the left side will have the same steel bearing housing as the pantah (and subsequently all modern beltdrive ducs) together with the angular contact bearing (7207). This is because the angled primary drive pushes the crank to the left under accelertion and therefore almost all of its rotating life.
The right side will get a conventional ball bearing to take the radial load and the occasional axial load during engine deceleration.
The crank does need modding to get the oil into the crank (right side) and to both bigend journals. Oil supply will be from the oil gallery where the oil pressure sensor is located.
right side welded up to add material