tony27 Posted August 1, 2012 Report Share Posted August 1, 2012 I think he is talking about the crank seal rather than bearing getting oil contact from both sides. As such I haven't had a crank seal let go but have had the dreaded noisy mains a couple of times & have always replaced the seals at the same time Quote Link to comment Share on other sites More sharing options...
2stroke4stroke Posted August 1, 2012 Report Share Posted August 1, 2012 Far from protecting the bearings from water I would have thought that a bearing sealed on both sides would be worse. If you fill the crankcase with ingested water I imagine the pressure will force it past the seal and in to the bearing but the seal will prevent it escaping. The bearing then continues to run in this muck. If the bearing is open then the dirt escapes and, if you're fussy, you can flush the case with petroil mix to clean it out? Quote Link to comment Share on other sites More sharing options...
dadof2 Posted August 1, 2012 Report Share Posted August 1, 2012 #9 temperature. Many sealed indusrial bearings specify a maximum ambient / opertating temperature of 40 degrees C. Two stroke crancase temp is tyically 80 to 90 degress C. This 50 degrees difference make a huge diference to the viscosity and film strength of the lubricant. Cheers Quote Link to comment Share on other sites More sharing options...
baldilocks Posted August 1, 2012 Report Share Posted August 1, 2012 This is an interesting debate we can all see the logic in the bearings being open allowing lubrication of the bearing through the pre mix. BUT for some reason this system didnt work very well on the early shercos which regularly suffered from main bearing failure. I bought a new 2007 for the SSDT, bike never missed a beat all week but i had a couple of weekends spare in June so stripped the motor and replaced the mains as a precaution. I was surprised they were sealed but to be honest there was nothing wrong with the mains. Every Sherco since has had sealed mains and by and large this has cured the problem of Shercos needing Main Bearings very quickly from new. As posted above my 2011 sherco did loads of work but was on the original mains and seals when i sold it. Various bearings in a Gas Gas pro gearbox are also sealed and you would think they would be open and be lubed by the gearbox oil but thats not the case, or it wasnt on my 2009 model anyway. Whilst we as users of the product think we know better i cant argue with the facts I have encountered in my experience, the sealed main bearing lasts just as long as any other brand of bike and longer than an open bearing in a sherco ever did. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted August 1, 2012 Report Share Posted August 1, 2012 http://www.efunda.com/designstandards/oring/oring_chemical.cfm?SM=none&SC=Ethanol Have a look at the above link. The alcohol in fuels is ethanol and it should not cause any problem for nitrile seals. Cheers Quote Link to comment Share on other sites More sharing options...
copemech Posted August 2, 2012 Report Share Posted August 2, 2012 (edited) http://www.efunda.co...none&SC=Ethanol Have a look at the above link. The alcohol in fuels is ethanol and it should not cause any problem for nitrile seals. Cheers NOT ACCORDING TO THE SEAL MANUFACTURER http://www.tto.com.t...es/material.htm Edited August 2, 2012 by copemech Quote Link to comment Share on other sites More sharing options...
samy Posted August 2, 2012 Author Report Share Posted August 2, 2012 Jeez what a can of worms i opened up Thanks for clearing up some of my comments kris! BTW, the bike's running GREAT! cheers Quote Link to comment Share on other sites More sharing options...
copemech Posted August 2, 2012 Report Share Posted August 2, 2012 #9 temperature. Many sealed indusrial bearings specify a maximum ambient / opertating temperature of 40 degrees C. Two stroke crancase temp is tyically 80 to 90 degress C. This 50 degrees difference make a huge diference to the viscosity and film strength of the lubricant. Cheers Bearing specs here: SKF 6206 2RS1 TN9 C4/GJN 6206 Deep Groove Ball Bearing 30x62x16mm 2RS1 Sheet steel reinforced contact seal of acrylonitrile-butadiene rubber (NBR) on both sides of the bearing TN9 Injection moulded snap-type cage of glass fibre reinforced polyamide 66, ball centred C4 Radial internal clearance greater than C3 GJN Grease with polyurea thickener of consistency 2 to the NLGI Scale for temperature range –30 to +150 °C (normal filling grade) Quote Link to comment Share on other sites More sharing options...
copemech Posted August 2, 2012 Report Share Posted August 2, 2012 (edited) Jeez what a can of worms i opened up Thanks for clearing up some of my comments kris! BTW, the bike's running GREAT! cheers Just be ready to replace them seals again in a few months! I will take the insurance and use the Viton seals, time will tell, yet it has been a couple years already! Thankfully most bikes are coming with such things as the alcohol resistant float needles in the carbs and such. It is a bit of a new world in dealing with this crap, and I do not have all the answers. Edited August 2, 2012 by copemech Quote Link to comment Share on other sites More sharing options...
samy Posted August 2, 2012 Author Report Share Posted August 2, 2012 Just be ready to replace them seals again in a few months! I will take the insurance and use the Viton seals, time will tell, yet it has been a couple years already! Thankfully most bikes are coming with such things as the alcohol resistant float needles in the carbs and such. It is a bit of a new world in dealing with this crap, and I do not have all the answers. Thanks for the reply copemech, I plan to change those seals fairly regularly! That is, if i don't get that 4 stroke beta i may or may not have fallen in love with last weekend... Quote Link to comment Share on other sites More sharing options...
stpauls Posted January 1, 2016 Report Share Posted January 1, 2016 Interesting thread on Sherco main bearings and crank seal failure Quote Link to comment Share on other sites More sharing options...
pauls320 Posted January 4, 2016 Report Share Posted January 4, 2016 Very interesting indeed...Fully sealed main bearings in a fairly low performance motor like a trials bike sounds like a poor cheap bandaid by factory for possibly low grade bearings and owners ingesting mud/water etc into motors, it does not protect the conrod bearings at all. Good quality 2t main bearings with quality premix easily last many years in extremely high load mx and chainsaw motors that run pretty much WFO day after day so the open mainbearing concept is not the problem. The companys just need to allow for proper premium grade bearings in proper spec. for load and owners just need to keep filth out of the intake tract. I guess the fully sealed bearings keep initial cost of bike down and visits to dealer service dept. up...just like all the new cars and truck, engineered to be in for servicing more often. No thank you Quote Link to comment Share on other sites More sharing options...
tony27 Posted January 5, 2016 Report Share Posted January 5, 2016 The fully sealed bearings are good quality SKF bearings running polymide cages which are used for noise reduction, the quality of them would be equal to or better than most mx bikes The unsealed mains seem to wear & start rumbling without any problems occurring in the big end bearing/conrod Main problem is the owners allowing moisture into the motor either through not drying the motor out properly after a drowning or getting water into the airbox during cleaning but why the big end is unaffected is possibly due to the fuel mixture aiming directly at the conrod as it enters rather than needing to get outside of the crankshaft to lubricate the main bearings Quote Link to comment Share on other sites More sharing options...
crazybond700 Posted January 5, 2016 Report Share Posted January 5, 2016 Friend of mine had the older sherco, and the mains died, because he did not use the bike enough. I guess the open bearings ran dry and maybe started getting rust on them? Sealed ones might prevent this? Quote Link to comment Share on other sites More sharing options...
pauls320 Posted January 5, 2016 Report Share Posted January 5, 2016 Hm..So they are good quality SKF bearings then, and just some owners problem of water and dirt in motor and corrosion, ethanol blended fuel? Maybe the premix ratio needs to be changed to a little more oil content 60:1 or 50:1? Tiny bit more oil burned but not enough to worry about....not like its a huge enviromental thumb on the nose to the world like the VW diesel thing. Now keep water and crud out of motor and factory can go back to the open main bearings that are a proven design and last a long long time and riders can afford to stick with this brand of bike because they dont have to do expensive motor tear downs all the time, just seems like a bad temporary remedy for something that should'nt be problem if the bike it looked after properly. I like the Sherco brand but will not buy a new one if its got fully sealed bearings. Quote Link to comment Share on other sites More sharing options...
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