Crank bearing.

[evo550]

Currently chasing some bits for a Rotax 406 rebuild and have come across the crank bearings at $80 each for genuine !!!
the size is available at the local bearing shop for less than half the price, but the sales guy warned me that they may not be suitable for a two stroke crank application.
They are c3, 30x72x19, Des anyone know of other manufacturer that runs the same size crank bearings?
Thanks in advance.

[pokey]

23.6306C3   YAMAHA   SR500   1981-1982   SR 500 E / F / G / SP   Crank Bearings   30x72x19
23.6306C3   YAMAHA   YZ490   1982-1990   YZ490      30x72x19
23.6306C3   YAMAHA   XT200   All   XT200      30x72x19

http://www.bbimporters.com.au/search/index.php?step=5&make=YAMAHA&model=All&year=1982&category=Bearings+Crank

Should get you started on that

[evo550]

Thank you kind sir...

[Hoony]

6306 is a very standard bearing, C3 clearance is what you need and you are good to go, should be in stock at ANY bearing service. assuming there is no circlips on outer or recesses

https://www.thebigbearingstore.com/6306-2rs-6306-zz-radial-ball-bearing-30x72x19/

[evo550]

The Yammie ones come in at about $45 each, so sorry Rotax but not this time.
At $550 for a piston kit, pity I couldn't get on of these at the bearing shop...
Thanks gents.

[Nathan S]

Any decent 6306 C3 bearing will work perfectly.
There's no magic to main bearings - the manufacturer specced a certain size, with a certain clearance - there's no invisible "2T main bearing spec" specification...

[80-85 husky]

depends how long you want them to last Nathan. chinese metallurgy is not yet up to speed in some bearing applications.

[evo550]

Any decent 6306 C3 bearing will work perfectly.
There's no magic to main bearings - the manufacturer specced a certain size, with a certain clearance - there's no invisible "2T main bearing spec" specification...

Thats what I thought, but the bearing guy said that even though the fitting dimensions are identical there can be a difference in how many bearings they can fit inside the race, some applications require larger /less bearings, some require more/smaller bearings....

[Lozza]

No way I would put a C3 crank main in a Rotax engine. Been there they will last less than 100km C4 with a polymide cage or a NJ series cylindrical roller

6306 C4 TN9 or NJ306 ECP/C4

[FourstrokeForever]

No way I would put a C3 crank main in a Rotax engine. Been there they will last less than 100km C4 with a polymide cage or a NJ series cylindrical roller

6306 C4 TN9 or NJ306 ECP/C4

And that's the difference right there!

[evo550]

No way I would put a C3 crank main in a Rotax engine. Been there they will last less than 100km C4 with a polymide cage or a NJ series cylindrical roller

6306 C4 TN9 or NJ306 ECP/C4

And that's the difference right there!

It's what ATK spec'd

[Lozza]

I have yet to see C3's in crank mains in any Rotax engine

[Nathan S]

depends how long you want them to last Nathan. chinese metallurgy is not yet up to speed in some bearing applications.

Which is why I used the word "decent"...

[80-85 husky]

I missed that distinction, so quick to jump up and down in indignation my apologies

[pokey]

With a wrinkled brow my mind has developed a question. While i accept C4 are a better or upgrade from a C3 bearing in this situation.. yet yamaha and I presume most makers specify C3 for mains . what makes a rotax bottom end any better to warrant the use of C4? I havnt heard of many jap bikes having catastrophic bottom end failures and I assume they would do the same RPM and have the same loads as a rotax. What am i missing?