Upgraded bearings¿

[spyderdrifter]

I just did a search for this, but nothing came up. So I was thinking about all my upgrade plans and thought about some of the Parts I bought last year. I bought 0.020 over bearings to go with the 0.020 pistons thinking for some reason I had to because of the larger piston size. Obviously I was wrong about that. Was wondering though, what would be a reason to up-size the bearings? Never found a reason for this. Thanks.

 

[bryanwheat]

You only need thicker bearings if you have the crank cut. You need standard size bearings if the crank hasn't been cut.

 

[spyderdrifter]

Yeah, I've been made aware of that point since last year. What would the point of doing it be though? What's the gain? I do see how it would make any difference in performance.

 

[BogusSVO]

You grind the crank when it is worn past spec, then you use the over sized bearing on the under sized crank to restore vert oil clearance.

 

[WES_393]

You grind the crank when it is worn past spec, then you use the over sized bearing on the under sized crank to restore vert oil clearance.

Bingo.

When the crank journals have been damaged or worn down, they are resurfaced which takes some of the material off. To keep the correct oil clearances, the bearing must replace the amount of material taken from the crank. Even micropolished cranks need "undersized" bearings to maintain correct oil clearances.

 

[spyderdrifter]

Spiffy. That clears that up.