Crankshaft main bearings

[samandkimberly]

So I noticed that one of the main bearings on my crankshaft is looser than the other so I'm replacing it. It's a Koyo 6307 SH, and I just spent a bit of time trying to figure out what the "sh" stands for. It took me twice as long because I originally thought it was "HS". Long story short; SH stands for "special heat" treated, and these bearings are rated for 6 to 10x the life over standard Koyo bearings:

http://www.koyousa.com/brochures/pdfs/cat199ex.pdf

These don't seem to be available outside Yamaha; I decided paying 2x the price over a standard 6207-c3 bearing for potentially 10x the life was worth it. Might just be marketing by Koyo, but it worked on me.

Sam

[DAVID THOMPSON]

i read some where that the wheel bearings on a bmw had a very long life span if greased proper
it was an unreal life span rating
i have over 600,000 miles on bmw and the only set i have ever had go bad was when
i hit a pot hole on i77 in ohio going to national rally at Shreve
it shattered both front bearings and the fork neck bearings were also replaced that fall just to make sure
plus xrayed the triple clamps wayne kelly in Pittsburgh pa took the kink out of the rim he was very good at that
dave

never did think being a cheap skate on bearings was a good idea

[Bill Jurgenson]

I wold say that is advertising hype.
Good industry bearings are just that, good bearings.

I use: 6307 C3 - you will find the bearing under this number regardless of maker. Both sides are the same.
C3 denotes the tolerance of the ball race; 1 very tight to 4 very loose, C3 is normally used for such purposes, C4 very often for 2-stroke racing cranks.

I use this bearing on the flywheel side but on the drive side I use: NU 307 ECJ

a roller bearing with loose inside ring. this bearing is much used in racing engines because it can take a much higher load and assembly and disassembly is much easier, too; the ring goes in after the crankcase is assembled.
It is, however almost twice as expensive.
I use SKF bearings myself.