Crankshaft bearings , where did they go?

[dr-alpina]

Has anybody an Idea how this could happen?

[johnjsy]

Hi Dr- , possibly the engine had not been started for a long time, the bearings became rusty, then when thr motor was started they very quickly self destructed.  Quite often a head or barrel as well if left off for various reasons, the same thing happens. Remember to use C3 clearance bearings on your re-build. Twostroke crankshaft bearings tend to run rather hot, the C3 bearings are a better choice. Hope this helps.........

[dr-alpina]

2 hours ago, johnjsy said:

Hi Dr- , possibly the engine had not been started for a long time, the bearings became rusty, then when thr motor was started they very quickly self destructed.  Quite often a head or barrel as well if left off for various reasons, the same thing happens. Remember to use C3 clearance bearings on your re-build. Twostroke crankshaft bearings tend to run rather hot, the C3 bearings are a better choice. Hope this helps.........

Hi Johnjsy, i have c3 bearings in another Alpina I restored one year ago and use as daily driver. there is some up and down movement at the crank (very little) thats normal at C3 ?

[grib]

Looks like the bearing cage is missing, could have been a plastic cage that has disintegrated?

[peterb]

Hallo Dr A, even with C3 clearance there should be no up/down play along the crankshaft, I would suspect the bearing manufacturer. Taking in water through the carb and letting it sit in the crankcase would also cause such a problem. Bye, Peter B.