Ignition side crank bearing failure?

[wence]

Just out of interest.
How many on here with 07 model 300's have had ignition side crank bearing failures?
Myself and another bloke here in Adelaide have both had the same bearing disintergrate on our 07's.
His a 250 and mine a 300.
Just curious as to whether it may have been a bad batch of bearings or just a coincidence?
Cheers Mark

 

[mattholew]

Old thread, but just thought i would add, my 2001 suffered a left side bearing failure.

 

[roostafish]

My '99 six days bike blew that bearing with only 54 miles on the bike, 8.5 miles into it's first race. Throughout that season I replaced the crank bearings a total of four times. We tried many things, after selling the bike super cheap to a friend, he blew it twice more. Finally he had to machine the crank down a couple of mils. He eventually sold the bike through our dealer. To my knowledge, the bike is still owned and ridden fairly locally.

 

[wence]

I had the crank balanced to almost perfect( twice as good as from the factory ), although he said the factory had done a good job beforehand.
Touch wood , it has been fine ever since.
Cheers Mark

 

[GMP]

Older bikes had 6306 ball bearings, and some had too tight press fits causing this problem. The newer bikes have a roller bearing. Rollers operate at a higher clearance, which is why you can detect some radial play which is normal. They also like more oil, which is one reason I like to run 36:1.

 

[Zeal]

Which model has the roller bearings? My 2010 ec 250 race has ball bearings on both sides of the crank?

 

[GMP]

The '02 or '03 to '07' I know have rollers. Aren't the new bearings sealed and use internal grease for lube, not the 2-stroke oil? "08 or '09 + correct? These would be ball bearings I suppose.

Grab the flywheel and pull up and down. If you can detect play the motor either uses a roller bearing on the ignition side or you have a trashed ball beaing.

 

[roostafish]

Yikes! Sealed bearings in the bottom end? They must be good, because my bike has a lot of miles on it, it's still quiet and feels tight.

 

[stainlesscycle]

Yikes! Sealed bearings in the bottom end?

if they are infact sealed i'm assuming sealed outside only - they gotta be unsealed toward the crank wouldn't you think?

 

[GMP]

No, sealed as in sealed up tight like a wheel bearing with its own lube. I'm sure its something a bit more special though. I remember Steve or Mark talking about this after a factory visit, maybe it will come up in a search. "08 or '09.

 

[CDBiker220]

Just curious. I have an 07. Would you be able to replace the bearing it it with the newer 08+ ball bearing?

 

[wence]

I was told by Scotties dirtbikes over here that yes you can.
I opted for the original type as I was scared about the sealed unit and oil lubrication.
Cheers Mark

 

[widebear]

I'm thinking I like the idea of a sealed bearing. By the time it starts making noise and you take heed the material is probably still contained in the bearing assembly as opposed to orbiting around the rod big end bearing and vice versa. Not to mention of keeping the dirt away from the bearing when you water out.

 

[wence]

Good points Widebear, I guess I was worried that the bearings would not have enough grease in there to keep them lubricated.
Cheers Mark

 

[stainlesscycle]

I'm thinking I like the idea of a sealed bearing. By the time it starts making noise and you take heed the material is probably still contained in the bearing assembly as opposed to orbiting around the rod big end bearing and vice versa. Not to mention of keeping the dirt away from the bearing when you water out.

it did say sealed, not shielded...if that bearing comes apart at any velocity, i would think bits are gonna get by a wimpy bearing seal.. and the normal crank seal should stop dirt from water...

 

[widebear]

it did say sealed, not shielded...if that bearing comes apart at any velocity, i would think bits are gonna get by a wimpy bearing seal.. and the normal crank seal should stop dirt from water...

Not on open bearings if the dirty water comes via the carb centrifical force is going to pull it right into the bearing , same way as it does the oil from the pre mix.. Been there.

 

[Vindicator]

This is a bit scary... what is the life expectancy of this sealed bearing? Why would this be a better solution than a bearing with no seal ? I have not seen this on any other 2 Stroke and they last for ages. Any clues why GG went with this choice ?

 

[GMP]

Widebear is 100%, been down that road too. Not sure of the sealed bearing life expectancy, but I'm sure they were life tested. Again this is not just a standard grade like youd use for a wheel bearing stuck on the crank. I'm sure the specs are somewhat specialized for the application. The two piece roller bearings have also been used on KTMs for years.

If I had to guess, and this is only a guess, I'd say its something that they (or others) played with while exploring direct injection.

For you guys with older bikes with the 6306 ball bearings, you can use an M306, which is a heavy duty version of the 6306 with an extra ball and a machined brass cage. From Worldwide Bearing, the cost was the same as the standard 6306 would be from the dealer. My old '00 XC250 in my friend's hands is still running today after being rebuilt with these bearings in '02.


Edit:

Here you go.

http://www.gasgasrider.org/forum/showthread.php?t=1950&highlight=sealed+crank+bearings

Done for emmisions reasons, lean oil ratios. At least they say its possible.

 

[elemetal]

On a side note to this, the Gasser trials bikes (TXT pro's) use a small oil passage from the tranny to oil the mains. This allows them to run 80 or 100:1 ratios and lower emissions. Seems to work well for that use; is it possible they are doing the same thing with the newest bearing style? Sealed with a hole in the race for tranny oil to circulate?

I prefer the roller bearings, much stronger when dealing with radial loads but that is for a bigger motor. The LC-4 motors around '01 used ball bearings for the left main and many had HUGE issues with these. In '03 KTM upgraded that part to a roller (that was also the 'fix' for the earlier ones); later it was determined that KTM had a bad batch of bearings for earlier bike with the same design (ball bearings) had no issues.

 

[widebear]

I think those sealed bearings are an indicator that development is moving ahead and that the two stroke engine is going to be around for a long time to come, albeit in the direct injection form.The whole idea of a direct injection system is to reduce emisions, oil in the premix not being desirable. I think the trend with these sealed bearings will ultimitely end up being a two stroke engine that does not require a total loss lubrication system in order to survive as well as comply with future mandated emision requirements.