Why Does Yamaha Have So Many Crank Bearing Sizes?

Ever wonder why Yamaha motorcycle, ATV and side-by-side engines have so many crankshaft bearing sizes? And is there really much of a difference between them?

Partzilla’s Yamaha powersports expert John Talley hosts lives Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this session, John was asked why there are so many crankcase bearing variations for Yamaha engines.

Yamaha powersports engine crank bearing sizes

Yamaha Engine Crankcase Bearing Sizes Q&A

Did Yamaha always have 18 different crank bearing sizes in their models? Are case tolerances that varied?

John Talley: They’re covering one extreme to the other. But I can tell you, on just about all the Yamaha engines I’ve built, their tolerances are actually very good, and it’s a little bit of overkill. But you could just about always throw a set of greens over blues, or is It browns? Greens or browns in a case, because those are in the middle and it would be fine, honestly. But they’re so particular and they want it to be so accurate, that’s why they have that wide of a variation. And honestly, it’s really not that big of a variation from their thinnest bearings to their thickest. But they just really wanted to dial things out, and dial things in perfectly. 

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Watch the video below to see how to size the crankcase bearings for a Yamaha R6 motorcycle.

Watch the video below to see how to install crankcase bearings on a Yamaha Raptor 700 ATV engine.

Watch the video below to learn how to size the crank bearings for a Yamaha YXZ1000R side-by-side.

Want to see more live repair questions answered? See more motorcycle and ATV repair questions answered here.



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