Hello folks!
So far I have read several threads on this site about wich bearings I am supposed to / can use when I am rebuilding my engine, and I find them really useful.
I have owned my bike, an XT600-2KF, -89 since 2002 and about a year ago i decided to rebuild it with original spare parts from my local Yamaha dealer. And I still remember the cost... A couple of months ago I bought one more bike, same sort, different color, and this time I wanted to keep the price of the rebuilding parts down by buying all bearings in a separately bearing store. Not japanese bearings so to speak.
Im writing this thread as ment to be an object of discussion, what bearings XT600 owners can or should use in their engines. And offcourse The so called C3 play question: to have or not?

Here comes something to start with:

Crankshaft:
Must be C3 bearings, I believe that no Crankshaft is absolutely 100% straight, even if it is brand new you bend it a few 1/100mm anyway when youre doing high rpm:s, if you dont use C3 you worn out the crank-journals on the axle that lies inside the bearing.
Another reason, offcourse, is the heat!
6306-C3
6307-C3, Yamaha pdf says: 6307SH2-9TC4, C4-play=expensive!!= I dont think so...

Balanceshaft:
Question: Why does Yamaha use Koyo on the right side and NSK on the left side of the balanceshaft? They also have different Yamaha art. numbers, but i really cant find the difference between them. Cant even measure the difference in the play with a special 1/100 mm clock...
I have been told and have seen for myself that the left side of the balanceshaft can be worn..? C3 bearings or not?! Does this axle bend itself under high rpm:s? I have anyway hard to think so. Standard play for me.
6305
6305

Transmission, In: clutch axle
6305N-C3 pdf-file from Yamaha says: 6305NRX1C3 so i think C3.
Other reason why it needs to be C3 is that it is possible that the axle bends itself a few 1/100mm or so when you drop the clutch standing still in first gear, thats when the highest amount of torque goes in to the gearbox.
6004-RSR, Oil Sealed bearing, works best with small play?!! Otherwise the sealing will be wornout very fast. I think?!

Transmission Out: sprocket axle, driving chain
6305-RSR, the original bearing from Yamaha have rather small play, i choose standard. Also because of the oil Sealing in the bearing.
6004-C3, Yamaha has changed the original part to a C3, thats 100% sure.

Gear Drum:
16005-C3 Stamped on the original bearing. I changed it "just in case"..

I can also tell I found out one of the significant differences in the number of balls in 6305 bearings. You know there can be 7 or 8 balls?!
Found out that a 6305 bearing with 7 balls can take 2000Newton = 200kg more in Dynamic Pressure( When it is rotating fast, with lubrication) But why does Yamaha still use 6305-bearings with 8 balls? Exept on one place in the engine: the one behind the sprocket/driving chain, it has 7 balls??!
My first thought was: It could have happened someting in the bearing industry in the last 20 years, but then I bought brand new (Yamaha original spare parts) japanese ones with 8 balls....

If there is someone who thinks they know something useful, maybe that can change what I wrote above, then I certainly would like to hear it!!
Get the words out!! Speak up!!

Best regards from "the swede"

Carl Henrik

could you give us a bit more info please ?

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Yamaha TT600RE 2004
Yamaha YZ250 2 stroke 99

Hehe

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2006 XT660R daily ride, 1994 XT600E about to be reborn, Blog: http://goingfastgettingnowhere.blogspot.com/

Would you really like some more info about bearings?

If this looks too much to everyone, maybe I can give you a shorter version, that seems to have worked out fine for a few others:

Crankshaft bearings must have C3 play. Also the Gear drum.
To minimize the wear of the 4th and 5th gear sprockets in the gearbox you can put in the rest of the bearings with standard play!
Thats All!

You just have to change the service interval, mostly the oil changes, whats in the oil, and it just got more important to check the oil level...

And some people also say there is no point to have a C3 bearing if you have a regular bearing in the other end of the axle, vice versa.
That seems logical to me.

After all the research i have done in this subject maybe the most simple solution is the best... Also the cheapest.

Any other thoughts about the XT600 Engine bearings??!

/ Carl Henrik

Carl Henrik.

Thanks for this thread. Most interesting.

I read someplace that crankshaft bearings are “special” bearings that you should not buy from the local bearing house?? (This was not for an XT, but a 2-stroke MX bike, but I guess the same should apply) Have you heard this? Do you know if there is any difference in “genuine” bearings from the dealership and “ordinary” C3 bearings from the local bearing house?

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Yamaha XT600E '01, Honda XR400 '03, Yamaha XT550 '83

Hi Carl Henrik,

Please excuse our British sense of humour.

Cheers.