08 Rev 3 Crank Bearing Confusion

[ashesman]

Hi all,

 

I have a 2008 Rev 3 270.  Engine is stripped down for a rebuild.  I purchased new main genuine Beta main bearings and they come with seals in them (SKF 6206-2RS1TN9/C4GJN).  The supplier says that is how they come in the new bikes now?  Can anyone please give their advice if I should leave them in or take them out?   I noticed the photos in the 09 service manual show metal shields fitted to the main bearings!  The seals look a bit special unlike the normal flat seal fitted to normal bearings.

 

Leaving the seals in bearings:

- Reduced crank case volume

- Potential longer life (if they survive)

- Allows leaner oil mix

- Potential for either limited side seal lubrication OR

- Potential for build up of oil in the side seal area that may spill into crankcase if the bike goes upside down

 

For taking them out:

- How I have seen it in most engines

- Ensures airflow/lubricant flow as designed by the manufacturer (assuming originally fitted without seals).

- Seals may not be correctly rated for oil/fuel

- Bearings may not have correct temperature rated lubricant in them

- Pressure pulsations in crank case damaging seals or popping them out or pumping lubricant in/out.

 

Does anyone have experience rebuilding these engines that could offer advice?  I am actually not worried about the bearings surviving with the seals left in but the effects of limiting air flow/lubricant to the side seals.

 

My first main bears did 300 hours and got slightly grumbly, second set did 80 hours and got so hot they broke a cage and seized (although I may know why but want to stay focussed on this topic!).

 

Any help appreciated

 

Ashley

 

Edited January 27, 2016 by ashesman

[worldtrialchamp]

I'm too lazy to attempt answering all your questions but I can say I've rebuilt a few different model rev3s using both genuine and aftermarket bearings. The genuine ones came without seals, the aftermarket ones came with and I removed them.

I have my doubts many if any of the dealers would purchase their 'genuine' bearings from the Beta Factory...but I've been known to incorrectly assume from time to time

[capper]

Never seen seals on crank bearings, would stop oil getting to them surely? BTW been working on engines over 50 years

[2stroke4stroke]

It seems to be done but the reasoning is beyond me.  Why seal a bearing when it sits in a constant supply of fresh lubricant mist?

[naichuff]

Having a BETA REV3 200 OF 2003 had to change the main some years back the old ones were sealed and the new ones were also sealed The old set were originals So did the bearings change to unsealed on later models?

[johnnyr1]

I know it's not quite the same, but when I stripped my '11 evo (owned from new), it came with metal shields in! Recently done a Sherco to, and it had shields as well. Also the shields seal the oil (pre-lubed from manufacturer) into the bearing. Seem to be the modern way!

[motomanandy]

From a mechanics point of view unless asked otherwise I would remove the seals.

The reasoning behind this is I've changed hundreds of Sealed bearings in my years and noticed the bearings 9 out of 10 are brown/ blue and cooked and all the nice clean grease thrown to the sides away from the bearing.

Just my opinion.

[reggie]

I think you mean that shielded bearings are used. I would replace with these same bearings.

[copemech]

That is the same as the Sherco factory bearing which is sealed. Perhaps Beta has seen fit to change as well.

[ashesman]

Thanks everyone for your feedback.  So, I am still on the fence about what to do!  The easy option is to pull the seals out and just put the bearings in and carry on...  But, I quite like the option of running sealed bearings as an experiment but it seems that the bikes running them must still be too new to be being pulled apart.  I cant find any factual information on the number of hours people are getting out of sealed bearings.  I also cant find any factual information about the bearings being fitted to new Beta engines.

 

I did some research in SKF documentation and they have all the right seals, grease, cage and characteristics to work well sealed.  They are high performance SKF explorer bearings.  The seals in them are pretty clever looking and sit quite deep.

 

Sealed bearings can do thousands or more of hours in industrial applications so should be OK.  It is not the bearings I am worried about, more that the side seals get enough lubrication.

 

Funny how little decisions like these can really bring you to a halt!

 

[worldtrialchamp]

depends how long you'll keep the bike I guess

[johnnyr1]

The bearings I removed from my (owned from new) Evo 250 where 6206-2Z/C4. these are a metal shielded bearing, not a rubber sealed bearing like the part No you quoted! Send them back and get Metal shielded or open, do not use rubber sealed bearings on the crank!

Edited January 28, 2016 by johnnyr1

[steve_earle]

Surely the factories wouldn't use sealed bearings unless it was for a good reason.

 

I can see the pros and cons of sealed vs non sealed. I know of bikes with sealed bearings that are over 3 years old, used twice a month and have done the ssdt a couple of times and still on original bearings.

 

Or could it be that they want to sell some more bearings and gaskets in a couple of years time?

 

I would keep the seals in, If a bearing turns out to be faulty you have some sort of comeback to the dealer.

 

Beta recommend checking them before the ssdt if the bike is over a year old!!!!!

[dadof2]

There are advantages and disadvantages to sealed bearings vs unsealed. Sealed bearings do not withstand high sustained RPM as well as unsealed. Very lean 80:1 fuel :oil ratios provide barely enough lubrication for unsealed bearings. 

Engines using unsealed bearings generally have an oil feed hole from the transfer port cut out in the crank case. If these holes is not there I would be very wary of fitting an unsealed bearing when the OEM bearing was sealed.

 

On the evidence I have to date unsealed bearings usually last a lot longer than sealed bearings, however I have known unsealed bearings fail in under a year (probably due to water ingress) whereas I have never known a sealed bearing to fail at under 4 years.

[copemech]

I have no big issue with the sealed bearings. Mine lasted five years in my 07 bike before I sold it in 12. We are talking Sherco here, and I find it keen that Beta has gone that direction as well.

Sherco do have many reports of failures for which I believe there is a simple explanation.

The alcohol in the fuel deteriorates both the crank seals and the bearing seals!!!!!!!!!!!

When the crank seals go, the engine vacume pulses will blow through the lighter bearing seals wiich are only designed to hold grease in and keep dirt out. It then washes out the bearing. No Lube! Possible dirt!

On the Sherco, a Viton crank seal is available, not sure about the Beta if the OD is the same? This should add insurance to the wash out effect of bad seals.

Of course, if we could just get good fuel without the corn added, we would be in better shape, but that is not allways practicle.