You didn't say what bike or motor you have Jerrymond, it might help, but my guess is that you might have to replace the crank bearing which MAY be the problem.
Do the tests and checks before you worry about the bearings, after all the bearings have a "water resistant seal" to protect them from damage, so you might be OK.
Taking into account the fact that the motor and bearings are water resistant, and therefore "sealed" you would have to have been pretty agressive with the degreaser to damage the bearings.
If after checks you think it might be the bearing causing the problem, you can give it a light spray with lubricant like WD40 (don't go mad). If this improves the problem, they are lacking lubricant. If this turn out to be the case, you will need to replace the bearings, as they are generally sealed.
If you don't know how to do this I would get professional help, otherwise you could do even more damage.
Hope this helps.