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Engine bearings XT600-2KF
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!! :clap: Best regards from "the swede" Carl Henrik |
could you give us a bit more info please ?
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Hehe :)
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Would you really like some more info about bearings? :biggrin:
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! :thumbup1: 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... :unsure: 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? |
Hi Carl Henrik,
Please excuse our British sense of humour. Cheers. |
Carl Henrik, I sent you a PM, please be kind enough to take a look.
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Hmmm. I was not joking. I never have found out if “genuine” crankshaft bearings are indeed somehow different from “regular” bearings, or just three times more expensive.
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Hello folks!
Straightening things out: The bearing-standard-number that is stamped on a genuine Yamaha bearings outer ring doesent always say if the bearing are having the C3 play or not. Mostly cases it dont say. You have to measure it up yourself. But I suppose this could be different from Yamahappy to another brand, when the bearings are not japanese, FAG or SKF maybe. I have been lucky to have been helped by the local Yamaha dealers own mechanics :biggrin: who have told me specially that a crankshaft bearing always needs to have C3 play, because the crankshaft is never doing high rpm:s being 100% straight. even if it is brand new. Too much weight and force going on in there. AND ofcourse the heat, that will take away the play and just precise give enough space for lubrication. The conclusion would be: You should have C3 play on a 2-strokers crankshaft because the oil is only 2% mix with the gasoline, this makes the C3 play ( by the mechanics called "heatplay") even more necessary. And yes, it should be enough with a "standard" bearing from the local bearing store. :thumbup1: Someone who know something I don´t?? Regards Carl Henrik |
In my opinion Standard bearings from a local bearing store could be made of even better material than japanese ones mounted as "Yamaha Original".
You know the japs arent leading that development anymore. Depending on what bearing-brand you choose, you should look up the specific facts about the brand your local bearing-store sells, for example 6306 that are often used as crankshaft bearings, in this case you could check for the C value, Dynamic bearing capacity, and compare it to the same 6306 in the other original mounted brands list. If there is a difference, there you have it. I have learned in my former studies at The Royal Technical University in Stockholm how to test the hardness in a piece of metal, but in this case I leave that assignment to someone else, when I dont have access to the right equipment anymore... But I know Swedish bearings are good :biggrin: I hope this sounds what you asked for?!! Or even better I hope! Come on now, give me some info I dont allready know!! / Carl Henrik |
When I used to buy things like swing arm bearings for Jap Motorcross bikes they tended to be a funny Japanese size and you couldn't get them from a normal bearing supplier.
Yeah I was only joking Carl Henrik :) |
crankshaft bearings
Well, we are travelling on two Tenere´s - one has the original Yamaha crankshaft bearings in, the other had aftermarket bearings (german I think from Kedo). On this last one we had to change the bearings in Colombia - believe me, they felt like sandpaper when turned by hand. I estimate the lifetime of the original Yamaha bearings now in at about 70.000 kms - and still going strong. For the aftermarket ones, I reached 50.000 kms and was just in time changing them before anything worse happened.
I will go for the Yamaha originals in the future! BTW, the new bearings were marked with the 4 number code, no inidication of C3 or C4 and the letters ´SH´apparently indicating that they are specifically made for Yammie. Auke |
This is the kind of comments im looking for!
Witch bearings in the engine took the most damage? All of the engines bearings worn or just the crankshaft bearings? Do you remember whats the brand of the bearings you bought? The ones you bought, where they regular or stamped C3 ? And what was the condition of the gears in the gearbox? Mostly interested in the 4th and 5th gear sprockets. I can imagine this happens when the wrong kind of bearings are used, and thats why im trying to find out what is the big deal with the "genuine" ones. I mean, it seems a bit secret whats with the Yamaha genuine ones. One more bullet (8 instead of 7) for ex. in the 6305 bearings cant be the answer... In my case my last bike has done about 65.000km, and the oil I poured out told me I should give it a real survey. And if I still own the bike when it has gone about 50.000km or more, Im probably going to disassemble it again anyway... And then I can afford to switch the bearings again :biggrin: Now this is getting interesting. Regards Carl Henrik |
Oh, sorry i didnt see you wrote "were marked with the 4 number code, no inidication of C3 or C4 and the letters".
Probably were those ones not C3 IF they were something else than japanese... Could be a reason of the wear you describe. / Carl Henrik |
I bet, oil, service intervals,defensive/ofensive driving and so on has a lot to say to. Meaning its wothless to change bearings, if you run it like ypu stole while the bike being cold, low on oil, and with tight valves and so on.
Even theese things in low scale, could be the difference between 50k km and 100k km, no doubt about it. My 03 has done 72k km, ive ridden the last 22k of 'em with frequent oilchanges. The sucker has attended 2 enduros, and stuff like that, and still use no oil and sounds really healthy (fingers crossed) My buddys startet knocking before 20k km. Guess some are just unlucky :( When that beeing said, please contunie the debate and keep us posted. Uh, and it ya wanna, please explain the c3-thing stuff, gues it has something to do with tolerances? Im wondering, if you know the stock ones work, arent it worth paying for it you know for sure it'll work? :) |
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... :oops2: 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!! :thumbup1: 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 |
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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… |
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 |
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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. |
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. |
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.. :rolleyes2: / Carl Henrik |
bearings
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 |
Hello again folks!
I have been checking out the XT600E service manual(that can be found in another posted thread in here :thumbup1: ) a few times and it tells me about the same facts that I allready have discovered before... :rolleyes2: 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... :rolleyes2: 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 :biggrin: 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 |
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