Whats Yamahas reason for this?

jmp2204

jmp2204

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Mar 26, 2005
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eastern ont.canada
Lost an axle bearing chaincase side the other night,pulling it apart i noticed the upper bearing (same as lower) has a seal on it (the bearing) facing the chain ,but no seal on the clutch side ,Doing some research ,yamaha states in there manuals ,make sure you put the seal towards the chain,Why is this so importtant? i picked a 6205 bearing (double sealed) and am going to pop one seal off and use it.But it cannot get lube through the seal so why not use a double sealed bearing? Any body know what the theory is here?
 
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The seal will keep contaminants in the chain case from getting to the bearing.

Also the chain lube will get thru the seal.
 
if u change ur chain case lube regularly u can run a non sealed bearing. yamaha uses the seal on the inside "IMO" so that the mettal filings from the chain doesnt make its way into the bearing. but if u do ur oil once a year or every 500 to 750 miles "what ever comes first" ud be fine without any seals on the bearing and ur bearings would last longer then if they were sealed. we use unsealed bearings on our race sleds at work but changed the oil after every week end.
 
The theory is that, since there is no seal between the inner race and either axle where it goes through the bearing, that the chain case oil will make its way to the back side of the bearing and sit in the space between the seal and bearing(one in the chain case). This lubricates the bearing. The reason for not removing the front seal is that there may be small metal filings from chain and gear wear that will make its way into the bearing and cause premature failure. Also, when your cruising along that chain is throwing all the chain lube away from the bearing hence no lubrication. Hope that make sense. I had the same question one time.
 
jmp2204 said:
why don't they just run with a doulble sealed bearing then? thanks!
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I have done this and didn't seem to have any problems. I'm not sure why they don't do this though. Maybe the grease in the bearing does not react well with the chain case oil or something or maybe the chain case oil does a better job than the grease that comes in a sealed bearing. The bearing on the chaincase side always seems to last longer than on the clutch side.
 
jmp2204 said:
;)! thanks
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on all other brands I have seen the seals open to the inside of the chain case. Changing chain case lube is simple, and I have not ahd any chaincase side bearings ever go on any sled of mine. now the clutch side is another thing. Those seem to be the first to go (right after skid wheel bearings) even if lubed regularly.

I think keeping the side open to the chaincase lube also helps longevity due to more fluid to cool the bearing.
 
There is more to it than that, do a search and you should find lots of info.
 
The NTN double sealed bearing are cheap. The "Yamaha" branded bearings made by un-named company cost an arm and a leg. Go with the NTN's. They are the same bearing, just double sealed. IMO it is a better bearing than the "Yamaha" ones.
 
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