Ofcourse, obvious that the service intervals and the way you treat the bike has its part in this. And that makes the life of the engine unpredictable.

Suggestion in how your buddys bad-luck-bike became worn in about 20k km:
When i spoke with my local yamaha dealer about the differences in bearings, he told me that the japs manufactures a real BIG amount of bearings and it is known that they have some quality problems with the material, for that reason a few bearings can be made out of bad quality steel. With a lack of hardeness so to speak. But its VERY VERY rare.
His bike could have got one of those bearings...
Another reason could be that he has been riding a few times with low oil level...

A standard bearing has the tolerance play between the bullet and the inner and outer surfaces that is called C2. All standard bearings have it and therefor no one speaks about it.
A bearing with a heatplay is called C3, there is a bigger play when the bearing is cold. When it heats up the play disapears and there is just precise enough space to lubricate the bearing correctly under operation.
Another great thing is that its more tolerant if the axle is bended a few 1/100mm.

Why discovering this facts about bearings? I say that i know 2 european manufaturers who dont have any hardeness-quality-problems in their bearings. I just have to find out what type the original mounted japanese ones are, so I can choose the right kind of bearings. Then I can buy better bearings for aproximately half the price, at the same time that i almost eliminate the risk to buy a bad manufactured genuine Yamaha bearing!!

Not that i think the japs have bad quality, its just that I KNOW these 2 european bearing manufacturers have atleast the same quality, if you only choose the right bearing for the right place...!
s
No one who knows something more?

/ Carl Henrik

Can you tell us who the two European manufactures are? Are you talking about FAG and SKF?

I was hoping the standardization of bearing was more advanced. So two C3 6306 bearings from different manufactures are only alike regarding tolerances and dimensions? The quality and “hardness” (wear resistance) may differ? I don’t think the bike manufactures will make the bearing specifications available for obvious reasons.

As Panzer said some bearings in jap bikes are non-standard. For example the crankshaft bearings in my old KX250 were of non-standard dimensions, only available from Kawasaki…

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

Yes, the manufacturers i had in my mind was SKF and FAG.
Can anyone say that they makes bad bearings?? In that case they would not have lived today. I know that these manufacturers bearings are often used in the heavy industry, they dont have a bad reputation so to speak...

The size of the outer dimensions of the bearings (in XT engines) are built in a standard ,as 6004, 6305, 6306, 6307 and ofcourse 16005. But whats inside thats so special about the ones KOYO and NSK manufactures???

I have thought about if the number of balls in 6305 (for example) has a difference:
7 bullets, that I know SKF and FAG use in this bearing have a higher Dynamic bearing capacity, but the ones KOYO and NSK delivers as Yamaha genuine parts with 8 balls maybe are suitable for higher rpm:s ??!! Anyone??
But thats not the big difference in the other bearings, its only 6305.

Ofcourse, the manufacturers are trying to sell as many genuine parts as possible, and some of them are often trying to hide the specifications of the bearings that comes as standard in a new bike, thats for sure, I agree. But within our bike we have an opportunity to get even better bearings if we discover whats the big difference!!!
And its presumably more than we have discovered so far... If there really is a difference. Or is it just a matter of choosing the right bearing with the right tolerance to the right place as I have mentioned before?

Anyone have any idéas about it?

/ Carl Henrik

Two 6306 C3 bearings from different manufacturers are APROXIMATELY alike regarding tolerances, IF you know they have them! It couldnt be the same cold-play if its not the same hardness and hardening in the metall, and if there are different sizes on the balls.
The outer dimensions on these bearings are the same, they are made in the standard 6306 and these digits say so.
The quality and hardness (wear resistance) COULD differ from one manufacturer to another. Doesnt have to differ.

And if your old KX250 crankshaft bearings were made in non-standard dimensions, bad luck. Thats not the case with our XTs, atleast not anywere in the engine, the swingarm bearings I dont know yet... havent done any research about those!

Another thing that crossed my mind is the difference in hardness that may appear from japs bearings to the european bearings:
If the european ones are made of harder material, they may be more sensitive when it comes dirt in it. The metal surface in the bearing maybe could get cracked more easily?? :confused1: Now im only guessing...

Even with this idea in my mind, I still believe the answer are to be found in this threads biggest returning question: C3 or not?

More qualified suggestions? Any thoughts about what I have written?

/ Carl Henrik

Could you share some of your chat up lines ?

Just go and buy the Yamaha parts, XT's and TTR's are not the highest quality Bikes Yamaha have made but I'm sure the engine internals will be Japanese quality.

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Yamaha TT600RE 2004
Yamaha YZ250 2 stroke 99

Carl, thanks for this thread. Really good.

Btw, sometimes the manufactures don’t make the right choice. I bought a new KTM520 in 2002. It had some crap camshaft bearings. The bearings were made in TAIWAN, I don’t remember seeing any numbering/id on them at all, so I don’t know who made them. Many KTM’s in 2001 and 2002 suffered major engine damage when these bearings came apart.

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

Ofcourse it happens from the start that the constructor choose the wrong kind of bearings, as in the KTM520 -02 maybe the camshaft bearings where too weak, they maybe would have had a longer length of life if they had higher Dynamic bearing capacity, a bigger size so to speak. And maybe the wrong tolerance play in the bearing is a part of the solution in that case. Even the lubrication of that bearing could be a part of the solution.
But thats not the case with our genuine bearings in our XT engine. They tend to do the job allright, but I believe it could be better ones.

I dont really think there is a specific reason for us to be negative regards "non genuine bearings". Specific to the 2 manufacturers i have mentioned before, their reputation is just too good for that.

Would you guys buy a bike with genuine japanese bearings if you would have the chance to buy the same bike model with european bearings that YOU KNEW lasts just as long(or even longer) but for lower price??? Sorry, but maybe im just not stupid enough to do so, I hope you've noticed it...

Im just beginning to think this "length of life" bearing-question REALLY IS just the matter of doing the right choise of bearings, and how we are going to discover whats the exact specifications of the "genuine" bearings in our engine are. Im not going to buy all of them genuine bearings again just to measure them up, because that can only be done when the bearings are brand new and unused, but maybe thats the only way to find out the exact specifications(even the hardeness), IF we cant argue our way forward to the right ones!!

This is almost beginning to be an industrial spying business..

/ Carl Henrik

Gentlemen,

Sorry for replying late on your questions - travelling you know.

As said, new original Yamaha crankshaft main bearings were put in in Colombia. The official Yam workshop manual definitely specifies C3 or C4 even - I have seen it but cannot recall exactly which. The original Yamaha bearings themselves are not marked with the C - number.
The failed bearings were of German manufacture - a well known brand but again forget which one.
The story about European bearings being better than Jap ones seems highly unlikely to me. Vice versa, the story that Yamaha gets especially good bearings from their Jap friends as well.

In my almost 240.000 km Tenere / XT600 experience I have found out that in the end the genuine Yamaha stuff proves to be better: gaskets, bearings, valves, you name it. If you stay close to home and continuously have access to repair facilities and parts, by all means go for the non-genuine. When travelling, or just not want to spend a lot of time getting hands dirty, go for the genuine stuff.

Auke

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Auke
http://aukemarieke.blogspot.com

Hello again folks!

I have been checking out the XT600E service manual(that can be found in another posted thread in here ) a few times and it tells me about the same facts that I allready have discovered before...

On the older XT600-2KF the specification of the bearing on the left side of the crankshaft is unknown.. But the eyes can tell atleast its a 6306. But the right side seems to have the same specification as the E models both bearings on the crankshaft: Bearing 6307SH2-C4. In my research I have discovered that this bearing 6307(and others) C2-C3-C4 tolerance depends on the manufacturer who made the bearing, its not always C4 !! Or C3 or C2. The same letters doesnt need to be the same tolerance play under measure! (I hope my point got through before in this thread.) Another thing I have discovered before: C3-coldplay is made to disappear when the bearing operates at high temperature, while the C4 play maybe never disappears totally. Thats why the C3 mostly goes by the name "heatplay" and the C4... I dont know. Yamahas mechanics only told me it was "special".. This could be a reason(one of them) of the shorter length of life when we use bearings with ordinary heatplay instead of C4... as in the manual... Maybe I have to do some more research about C4...

Ofcourse, I agree, mostly the Yamaha Genuine Parts as gaskets, valves, springs, pistons, clutch-parts, steel-wires and more is the best for the bike. Also little more expensive. And maybe not as exciting to use either
Have to say that I always have used genuine parts, no matter what the bike or manufacturer, but sometimes EXEPT for the bearings!
This kind of experiments is only recomended when you use the bike inside your own country, wouldnt recommend to do it longer round trips abroad.

The quest for the exact bearing-specifications continues. Only maybe a little bit slower than before...

/ Carl Henrik