Re: yamaha 650 engine bearing noise?
I doubt he heard an engine berring noise, what he probably heard was a pump noise,, to inspect the main crank berrings you must break down the engine and spin the berrings with your finger,, here is what you can check, with the starter in you can first do a compression check, if that is ok you can check end play in the conecting rod berrings, with plugs out, rotate the engine by hand when the piston passes top dead center hold the rear flywheel tight and push down on the top of the piston it should be tight if you feel a clunk there is a problem with the rod berring, do this to each piston and see if it is tight. if there is no free play you have checked about all you can accept for pulling the front and rear seals and visually inspecting those berrings then install new seals, you may be able to see the berrings in the case by removing the reed valves and look for rust but it is difficult to see a slightly bad berring that way, I have looked at a lot of berrings but without spinning them individually out of the engine it is a guess at best. if an inner berring is bad you really can't replace it by yourself any way since the crank is a pressed crank it usually calls for a new crank or a rebuilt crank. most high pitched squeeling is caused by the pump so he probably guesed wrong as to the origin of the noise.
