Chain Case Bearings?

taped throttle

taped throttle

Member
Joined
Oct 26, 2003
Messages
124
Age
62
Location
Rochester, NY
I took my chain case off today to start a long track project. When I took it out and set it on the bench I was looking at the bearing... and I don't understand why Yami installed them the way they are.

The bearings have a seal on one side, which is OK but the seal was installed facing the inside of the case. And that doesn't make sense. This leaves the ball bearings facing the tunnel, exposed to the elements (water). There is a rubber ring that seals around the shaft that runs through the bearing but that hardly weatherproofs it (I wouldn't want that sealing my rubber raft), I realize that it would be difficult for anything to get at the bearing but why make it possible. This also seals the ball bearings from being lubricated by the gear oil, this would seam reason enough to install them the other way. I could see using a bearing with seals on both sides OR installing the bearing the other way, seal facing the tunnel. Or were they installed wrong from the factory?

Does anyone know a reason why yami would install the bearings this way? :o|

I am seriously considering installing the bearing with the seal facing the tunnel, any reason I shouldn't?

Thanks for any input. ;)!

TT
 
I've kind of wondered about that one too. The only thing I can think of, is it prevents any metal debries from chain/sprocket wear, getting to the bearings. Some 90 wt does get to the bearing through the inner seal. Water is kept out, by the outer seals.
I usually pack the area between the outer seal and bearing with grease, while it's apart.
 
It's really my only beef with my Yamaha sleds. They don't need any extra lubrication getting to this bearing. Leaving it open exposes it to the metal shavings that the magnetic dipstick doesnt catch. Those shavings get into the bearing and cause it get rough and gravelly. I always replace mine with the same bearing number if I recall its 2062RS but the one with seals on both sides.
 
i run my bearings with the seal on the tunnel side, open to the chaincase, but i change my fluid every 1000-1500 miles
 
It was explained to me like this...... They pull only one seal on each bearing facing the tunnel because chain lube will (through capilliary action) find it's way past the chain case and bearing to lubricate the ball bearings... Also, capilliary action between the shaft and the inner race will also let oil flow to the unsealed side of the bearing.... It's claimed that debris and shavings are too large to get past with this capilliary action, thereby staying inside the main portion of the chain case.... Keeping the seal on the gear side of the case, then keeps out these particles thus keeping the bearing lubricated with "filtered and clean oil only"....

This was explained to me by a very senior and experience member from this site... everything he said makes good sense to me...

When I asked the senior mechanic at Yamaha (where I try not to go), he said "I don't know why they leave a seal out... are you sure it isn't the seal on the gear side of the case thay was left out?"....

He didn't even know which seal it was that's removed always....

Let me grab my wallet and go for service at 70 bucks an hour....

hope this helps...
 
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Bearings

TJ500 is exactly right. They utilize the relatively tight slip fit between the axle shaft and inner bearing race as a crude filter to filter out the big stuff. Capillary action ensures the bearings get lube. Pretty ingenious design actually. I still feel that it's better to keep the chaincase lube out so I always install 6205 2RS bearings (2RS means 2 Rubber Seals). I've been doing this for several years with good results. I guess it's really a matter of personal preference.
 
Yup it comes with 6205RU and you want to replace it with 6205RS I gues RU means unsealed??? Anyway it's not really very ingenius if the bearings are getting contaminated with debris and not rolling smoothly after only a few hundred miles. I parted out two Vipers this fall both sleds had 700 miles on them and both lower chaincase bearings were rough already. I've replaced all my Yamahas with the 6205RS and the bearings were still smooth as silk after several thousand miles.
 
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