My friend has just seized his 2010 300, he has found that a main bearing has seized, he is telling me that the bearings are sealed on both sides. I find it hard to believe this is right as they won't get lubricated, is this right? He has been told this was introduced on the 2010 model?
Sealed main bearings?
- Thread starter hallam76
- Start date
Berkyboy
Site Sponsor
My understanding is starting in about 2008 to meet new emission standards the 200/250/300 bikes had to be able to run at basically 100 to 1 ratios not just the 50 to 1 that the sticker says on the fuel tank.
That being said the only way to achieve this safely with a carburator is to go with sealed crank bearings.
You don't have to replace the main bearings with sealed ones if you don't want to as the regualar bearing are still available.
Hope this helps.
That being said the only way to achieve this safely with a carburator is to go with sealed crank bearings.
You don't have to replace the main bearings with sealed ones if you don't want to as the regualar bearing are still available.
Hope this helps.
This would mean two ball bearings on the crank instead of the previous one ball bearing/one roller bearing setup.
Are these seals the same as an industrial bearing? The standard rubber seal can be removed to make the bearing RS instead of 2RS. Put the open side to the inside and run 50:1 and everything would be fine.
Are these seals the same as an industrial bearing? The standard rubber seal can be removed to make the bearing RS instead of 2RS. Put the open side to the inside and run 50:1 and everything would be fine.
widebear
Banned
Thats right two ball mains. If I remember correctly 01 was the last year for roller bearings which is what failed on my 01, apparently not an uncommon of an occurence according to what I've read on here, but I've never personaly seen a failure besides mine. . That being said every brand has its issues and if it happens to a gasgas you'l probably hear about it on the site.
GMP
Active member
'01 was the last for 6306 ball bearing on ignition side. '02 to '07 had the roller bearings. '08 back to the sealed ball bearings. I have had a lot of hours on two 250s with the roller bearings, no problems. KTMs have run this setup for years as well. Roller bearings run at a higher clearance, higher load rating, but like more oil.
I'd be interested to see what the seals on that failed bearing looked like, specifically if they look like they were deteriorated by fuel additives. I hope they are Viton.
I'd be interested to see what the seals on that failed bearing looked like, specifically if they look like they were deteriorated by fuel additives. I hope they are Viton.
I expect it's more likely a lack of initial lubrication. Unless the factory orders something special, ball bearings don't come with much grease in them.
KTM/Husaberg uses 2RS bearings on their 4T camshafts. The seals keep out debris but motor oil does eventually penetrate past the bearing seal enough to keep them in good shape.
On a 2T crank, there probably isn't enough oil in the premix vapour to creep past the bearing seals.
GMP
Active member
Reason I'm thinking this is there is a guy on the ECEA site having a hell of a time keeping crank seals in two KX250s. They were stock, black rubber (probably BunaN) and come out hard after failing in a few months. I have a couple of rubber gas cap gaskets that hardened to the durometer of the cap itself. Now, no problem with GG crank seals because they are made of the right stuff. Lets hope the seals in these bearings are as well.
I'm wondering if the roller bearing is a better idea on the heavier flywheeled bikes?? Does the ignition side use a 6306 too ?
Theres an oil passage on each cheek of the cases for oiling the bearings so don't like the idea of a sealed bearing spinning at crank speeds without a good source of lube.
Neil, I think the premix lube comes down the oil passages to the outside of the bearing first, thru the bearing race into the crank case, so a seal on the outside may hamper that. Maybe get sucked thru eventually ??
Theres an oil passage on each cheek of the cases for oiling the bearings so don't like the idea of a sealed bearing spinning at crank speeds without a good source of lube.
Neil, I think the premix lube comes down the oil passages to the outside of the bearing first, thru the bearing race into the crank case, so a seal on the outside may hamper that. Maybe get sucked thru eventually ??
widebear
Banned
I would not be suprised that ,depending on the type of oil used in conjuntion with alcohol based fuels there could be some seperation if the bike sits for extended periods. Guys using to much oil,to viscous, wont be doing themselves any favors either.It is well known that most engine wear occurs at startup. At shutdown I allways give the hot engine engine some rpm while pressing the killswitch to help pre lube the bottom end bearings for the next time.
While a roller bearing has a higher ultimate load rating, I don't think they are necessary in a 2T. The last 2T bike I had was an ISDT Jawa from the 70s. It had roller bearings on both sides of the crank. The end play magnified the typical 2T load when going on-off with the throttle. I machined the bearing housing to reduce the end play to .005" and it was much better.
They had a neat engine construction. One piece engine casting. Crank came out the left side when the bearing plate was unbolted. Transmission gears came out the right side when the cover plate was removed. The odd part was the forward swinging kickstarter that engaged directly on the crank gear. It worked well.
A sealed bearing pretty much negates any external lubrication. If the oil passages you mention actually collected oil and kept it against the bearing, some might eventually get past the seals but I wouldn't count on it.
My 68 Bultaco had open ball bearings on both sides. The crank stub shaft had a short protrusion so the bearing wasn't right tight against the crank cheek. This left room for oil vapour to reach the bearings. A simple construction that worked.
I think it's like Glenn suggested. If a seal fails by hardening, the small bit of internal grease creeps out. Oil can't get in.
Most bearing seals fail at the inner race where the wear takes place. They are pressed into a recess in the outside race and sit stationary. I can only assume that the hardened seal contracts and creates a tiny gap to the outer race allowing the grease to creep.
After some horrible looking 'sealed' bearings I've seen in my wheel bearings I think they not be too sealed. I changed the rears twice last yr and were rusty as hell even though I checked and/or added waterproof grease. They may keep out chunks but I think fluids will eventually creep in, or out. In case you wonder what kind of bearings they were, one set was cheapo chinese and the other a name brand. The name brands were not as bad. Hardened wheel spacers are enroute to maybe prevent more grotty bearings.
Neil, I'll be taking my engine apart soon if you'd like to take a look inside. (if you haven't already). I'll be replacing the bearing behind the clutch (didn't have one available when I needed to put it together last time), centering the crank better and changing it back to a 300 (for a while).
Neil, I'll be taking my engine apart soon if you'd like to take a look inside. (if you haven't already). I'll be replacing the bearing behind the clutch (didn't have one available when I needed to put it together last time), centering the crank better and changing it back to a 300 (for a while).
HuskyDude
Super Moderator
I've ran 100/1 on my TXT for ever,,,but haven't tried it on my 300XC yet...
roostafish
Gold Level Site Supporter
Years ago I ran Amsoil 100:1 in a KTM 250. I blew the bottom end twice in a period of six months. The piston rings wore quicker than I had liked too. These days I'm a 28:1 mixer. More oil=less wear, better sealing, and believe it or not, more power.
I also know a guy who put a set of sealed bearings in the bottom end of an old Bultaco. It ran for many years with no problems.
I also know a guy who put a set of sealed bearings in the bottom end of an old Bultaco. It ran for many years with no problems.
Similar threads
