346 Crank Bearings

[blsnelling]

I recently rebuilt a non NE-346xp, and it had plastic cages. I took the bearings to a bearing supply house and they both cross-referenced to FAG 6202.c3. I specifically wanted metal cages. The two saws that I've seen with cage failure had plastic cages, a husky 350 and a stihl 180. I was told most c-3 bearings are good to 14-15k rpms. If you want to upgrade the bearing I was told it would cost 4x's more for a bearing with tighter tolerances, i.e. ceramic.

Since then I've been using c3 bearings with the seal on the outboard bearing side. I pack the the space between the the bearing seal and the crankshaft seal with a high grade/ high temp bearing grease. I don't race saws so reliability has precedence. I don't want any air leaks. The two saws that's I've done with the new bearings w/lip seal both run very smooth and I have yet to see any grease coming out from the crank seals so the pressure from the crankcase is not blowing by the bearing lip seal.

I wouldn't recommend this setup for a race saw as there is friction from the contact seals and the Kluber grease. I can feel it when you turn the crankshaft by hand, no piston or cylinder installed, so I would assume the unloaded rpm could be reduced. With the saw running I couldn't tell a difference though.

A ceramic bearing does not equate to tighter tolerances. That's what the tolerance of C0, C3, etc, is about.

Also, neither grease, oil or air should ever escape past a crank seal. If it does, it's a problem with the crank seal, not an indication of a bearing design flaw. You do not need sealed bearings or grease to prevent air leaks, nor should you rely on sealed bearing for that purpose.

 

[vw_motorsports]

A ceramic bearing does not equate to tighter tolerances. That's what the tolerance of C0, C3, etc, is about. A

lso, neither grease, oil or air should ever escape past a crank seal. If it does, it's a problem with the crank seal, not an indication of a bearing design flaw. You do not need sealed bearings or grease to prevent air leaks, nor should you rely on sealed bearing for that purpose.

The bearing is not a fully sealed bearing it's more of a hybrid. The bearing is open to the crankcase and the mix for lubrication. The grease is to keep the crank seal properly lubricated since the seal is no longer getting lubricated from the mix. The crank seals have a very hard life, and they can be damaged fom debris, saw dust etc. Without the grease I believe the seal would run dry and lead to failure.

 

[blsnelling]

I remove any seals on a crank bearing for those reasons. I believe Stihl did away with them as well. I understand what you're doing, just don't think it's necessary.

 

[vw_motorsports]

you may be right...it could be overkill

 

[blsnelling]

you may be right...it could be overkill

And you may be onto a good idea. It would take many hundreds, or thousands, of hours of testing to find out though.

 

[andrethegiant70]

Since then I've been using c3 bearings with the seal on the outboard bearing side. I pack the the space between the the bearing seal and the crankshaft seal with a high grade/ high temp bearing grease. I don't race saws so reliability has precedence. I don't want any air leaks. The two saws that's I've done with the new bearings w/lip seal both run very smooth and I have yet to see any grease coming out from the crank seals so the pressure from the crankcase is not blowing by the bearing lip seal.

Remember that this "pressure" is negative pressure. There is vacuum at the seal. Centrifugal force probably does the trick, though. The grease would probably want to spread out along the crank in this area.

I think you just came up with the numbers Mr. Snelling was looking for! Good job!

 

[blsnelling]

For my purposes, I definately do not want seals on my bearings. More seals equals more drag.


Here are some interesting tid bits about ceramic bearings.

Wikipedia:
Silicon nitride ball bearings are harder than metal which reduces contact with the bearing track. This results in 80% less friction, 3 to 10 times longer lifetime, 80% higher speed, 60% less weight, the ability to operate with lubrication starvation, higher corrosion resistance and higher operation temperature, as compared to traditional metal bearings.


From another site:
-Ceramic bearings have 1/10th the friction of steel which means faster ET's and lap times! Can you push your car with one hand?

-Silicon Nitrate balls weigh 60% less than steel balls of the same size. Reduce your bearing rotating weight!

-Ceramic Bearings last up to 5 times longer than steel!

-Ceramic Bearings have no micro weld adhesion between the balls & races which means lower friction. Ceramic also has a lower amount of thermal expansion which also reduces temperatures. Bearings run cooler and vibration levels are lower at high RPM

 

[vw_motorsports]

For my purposes, I definately do not want seals on my bearings. More seals equals more drag.


Here are some interesting tid bits about ceramic bearings.

Wikipedia:
Silicon nitride ball bearings are harder than metal which reduces contact with the bearing track. This results in 80% less friction, 3 to 10 times longer lifetime, 80% higher speed, 60% less weight, the ability to operate with lubrication starvation, higher corrosion resistance and higher operation temperature, as compared to traditional metal bearings.


From another site:
-Ceramic bearings have 1/10th the friction of steel which means faster ET's and lap times! Can you push your car with one hand?

-Silicon Nitrate balls weigh 60% less than steel balls of the same size. Reduce your bearing rotating weight!

-Ceramic Bearings last up to 5 times longer than steel!

-Ceramic Bearings have no micro weld adhesion between the balls & races which means lower friction. Ceramic also has a lower amount of thermal expansion which also reduces temperatures. Bearings run cooler and vibration levels are lower at high RPM

Have you been quoted a price on these bearings??

 

[andrethegiant70]

The other question is.....

Is the tolerance (c3, etc) a factor anymore, since the bearings will probably not expand the same way as steel ones?

 

[blsnelling]

Have you been quoted a price on these bearings??

I already have the balls. (Don't even go there, lol!) I just don't want to tear down my saw and find that it has steel retainers and can't be rebuilt with the ceramic balls. So I'm trying to source new bearings first that have nylon cages. The best full ceramic bearings us PTFE spacers between the balls. Even the races are ceramic. What I'm wanting to do would be considered a hybrid, using steel races and ceramic balls.

 

[Terry Syd]

Sealed bearings

Re the sealed bearings. You can get them where they are low friction, but I was thinking of using the shielded bearings. There is no contact with the inner race so there is no seal friction. The bearing grease would likely flush out over time and be replaced with the two-stroke oil. The shields would allow the pooling of the oil.

The reason I want to use them is to tune the base compression. I can stuff the center of the crankpin and use two sealed bearings to bump up the crankcase compression. If the powerband narrows too much, then I can take out one of the sealed bearings and replace it with a stock open bearing.

So, does anybody know what size bearings the Husky 450 uses?

 

[blsnelling]

The bearing supply house just called back to tell me that he can't find a 6202 with nylon cages. That seems really odd to me.

 

[vw_motorsports]

the bearings that came out of the husky w/nylon cages were SKF I believe. This saw had a nasty vibration because of the disintegrated cage. I was lucky it didn't wreck the engine.

 

[Jacob J.]

the bearings that came out of the husky w/nylon cages were SKF I believe. This saw had a nasty vibration because of the disintegrated cage. I was lucky it didn't wreck the engine.

Those came out of a 346NE?

 

[blsnelling]

Those came out of a 346NE?

I think he said it was an OE.

 

[Dan_IN_MN]

I already have the balls. (Don't even go there, lol!) I just don't want to tear down my saw and find that it has steel retainers and can't be rebuilt with the ceramic balls. So I'm trying to source new bearings first that have nylon cages. The best full ceramic bearings us PTFE spacers between the balls. Even the races are ceramic. What I'm wanting to do would be considered a hybrid, using steel races and ceramic balls.

Brad

How are you going to get the balls out and the new ones in? Do you have a plan of attack?

 

[blsnelling]

Brad

How are you going to get the balls out and the new ones in? Do you have a plan of attack?

I've done it before to clean bearings. You pop the cage out, move all the balls to one side, cock the inner race and remove the balls.

 

[wooddog]

I guess better late then never. Ceramics have been around for awhile now. Not only the hybrids, full ceramic races .

http://www.bocabearings.com/main1.aspx?p=docs&id=16

 

[blsnelling]

I've been on Boca's website. They do sell the kind of bearing I'm wanting to make. But I already have the ceramic balls and would like to make my own. But sourcing nylon cages seems to be about impossible.

 

[Saw Dr.]

I am going to pick up some bearings here this week. Will THIS work? Cage looks a little different than I have seen. There is a distributor not for from me in Atlanta. PM me if I can help.