Originally Posted by
Hyjinx
Hey all
Got a thought that lead to a question. Hobbsy posted a shot of a page in a magazine that made an interesting statement concerning crankcase lubrication.
Indicated the front bearing sheilded both sides and the rear shielded on the back( crankpin side).
I have done lots if used e bay motorbearings on Saitos. I have not done any motor I bought new yet. In motors purchased new, what do you guys find concerning shielding in motors factory assembled.
And secondly, the article indicated the crankcase vented between the bearings via the nipple (factory) between the bearings in the bottom of the case.
Wonder if the motors that vent through the rear cover may be shielded different?
What have you noted Saitoheads?
I can't remember all the bearing variations in used Saitos I've rebuilt and never rebuilt one that was rear cover vented. 4 strokes have more positive crankcase pressure than negative (barely) so I install double sided sealed bearings in the front (2RS) to keep from spuing oil everywhere. In the rear I install open retainer bearings.
Some have said that leaving a shield or seal on the front side of the rear bearing is a good idea for the rear cover vented saitos. I've also read to leave it on the back side for the same reason, that it helps to retain more oil in the crankcase but it doesn't make much sense to me. The source of the oil is behind the rear bearing (ring blowby) and the place that needs the most oiling is the valve train. That's why saito moved the vent from the rear cover to the cam gear housing, or at least that's my understanding. Based on that premise I would install open retainer bearings in the rear regardless of vent location.