F300 crankshaft thrust bearings

[choogenboom]

All online sources for Yamaha parts show the 2012 F300XCA crankshaft thrust bearings as "unavailable". Not out of stock but "unavailable" or "NO LONGER AVAILABLE". Without this part engines can not be rebuilt. Fortunately I cross referenced the part number and found the exact same part number IS available for other model year 4.2L blocks. Is this an error in Yamaha's parts database? And there are several sizes available, and again, as with my post on the bearing shells, there is no data available as the critical dimensions of the thrust bearings. Does anyone know the thrust bearing sizes and why they would be unavailable ONLY for the 2021 F300XCA?

7

BEARING, THRUST 1 6CB-11426-01-00

Unavailable

8

BEARING, THRUST 2 6CB-11427-00-00

Unavailable

[boscoe99]

Where exactly are you seeing the exact same part number for other model year 4.2 liter blocks?

I am seeing that in the middle of the 0113 production year the bearing part numbers were changed.

Earlier bearing part numbers are no longer available. There is no supercession shown for the old bearings to the new bearings.

bmm

[choogenboom]

"Where exactly are you seeing the exact same part number for other model year 4.2 liter blocks?"

I stand corrected. I am finding the pushing bearing (sorry, system wont let me say the salacious word that rhymes with "the rust") with different suffix numbers as shown in your image, I had assumed they were to show a different thickness but guessing that's not the case? So are those bearings the replacement for the 6CB-11426-01-00? Is it an error in Yamaha's database that they are not shown for the 2012 F300XCA?

[boscoe99]

The part numbers shown in the Yamaha parts catalog are the part numbers that were used in production. In the case of an 0112 production year 4.2 liter F300, bearings 6CB-11426-01-00 and 6CB-11427-00-00 were used. Those bearings are no longer available. There are no superceding part number bearings available to replace what your motor came with.

It is strange to me but I have never seen a specification for the thrust bearing.

[choogenboom]

Pretty sure only the upper thrust bearing is doing any real work as its supporting the weight of the crankshaft. Its thickness controls the crankshaft's vertical offset which is likely not considered a critical dimension. So is it safe to use the bearings used in later model 4.2L blocks?

[boscoe99]

I would think the crank shaft would be resting on the lower bearings.

I have no idea about the use of the later bearings. The way the part number is structured would tend to indicate it is OK but in Yams system the earlier part numbers do not supercede to the later part numbers.

[boscoe99]

At the time the thrust bearing part numbers changed, the block number changed.

[choogenboom]

I would think the crank shaft would be resting on the lower bearings.

Lets use the picture above for reference where the crank is oriented vertically with flywheel up which is the way the engine is oriented in normal running scenarios. In that orientation, if you look at the thrust bearings part numbers 7 and 8 they are located around the center journal, one on the upper side of the center journal and one on the lower side of the center journal. The upper thrust bearing is supporting the full weight of the crankshaft due only to gravity. I do not see anything that would cause a difference between the static and dynamic load on the upper thrust bearing and no source of force that would push the crankshaft up against gravity and put a load on the lower thrust bearing.