I'm planning to do the sprocket carrier bearing mod but unable to find any posts about it, can anyone help?

Try this:

http://www.xt660.com/showthread.php?t=21410

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thanks Pleiades, I'm planning to have the mod done very soon

I've had a second bearing fitted but now I can't refit the wheel. With the wheel spacers installed it's too wide for the swing arm so I'm thinking the new bearing is installed incorrectly.
The left wheel spacer is 20mm wide, how far should it protrude from the sprocket carrier when pushed into the seal?
What gap should I have from the left end of the sprocket carrier to the bearing face?

Hello All,
Just would like to pass on some advice if you are looking at doing the bearing mod to the cush drive, from a bad & expensive experience on the weekend that destroyed my swing arm & hub after the alloy casting broke away allowing the hub to move to the outside chewing into the swing arm & hub.
My bike had the double bearing mod (2 x 6304 2rs) that machines 15 mm out of you hub & 15 mm off the spacer leaving a small amount of alloy that stops the hub moving sideways. the better way to go may have been to use the wide alternative of the same bearing (62304-2RS) & machine out only 6mm giving a lot more support. another alternative may be to install a internal retainer clip to take some of the load if there is enough room, I have not had a chance to look at it yet but will keep up to date with how I go.
This did happen while riding in steep country with other bikes, lots of erosion mounds, and going hard with good traction, I have tried to attach some photos but no luck as yet ??

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That's a shocking failure and I'm interested to know how it occurred. I've had my hub modded for a few years now and give it an absolute hiding and it's great, even the rubber Cush rubbers are lasting well. I can only guess something went amiss with the machining or overall install and I hope you sort it out as that damage looks expensive.
Matt.

i was thinking about having this mod done, but after seeing this i'll give it a miss. did you have the machine professionally machined or do it yourself?

SKF bearing number is?

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Yes, It is looking expensive and am trying to source a used swing arm, The double row SKF 22.2mm wide bearing looks to be the best option as you are very correct that there is not a lot of the body left to retain the bearings.
I was very careful when seating the bearings & not driving them home too
hard & the machining was checked both ways as to not take too much out.
I also cross referenced it before & after the mod to check for myself that the overall width had not changed.
All I can put it down to is having really good traction, damp rocky loamy ground, steep smooth hills for a long period, lots of erosion mounds, a KTM 525 just in front of me, landing off the erosion mounds then powering on hard with the wheel getting driven into the ground hard getting maximum traction & little slip in second- third gear putting huge loads on the hub.
The hub had near no play in the rubbers as I checked it the day prior riding in the Snowy Mountains, I will get it apart again shortly & add some more photos, The 2 photos that I put on in the first note are when I got home after recovering the bike & putting the wheel & hub back in the correct position. All I can say is if you have the double mod done is to keep an eye on it especially the alloy casting inside the hub for any signs of cracking off the retaining section that is about 2.5 mm thick approx.
All I hope is that I can help in that we can all learn from my misfortune.

Ahh that answers my questions...I never thought anyone would machine out 15mm and fit TWO bearings...thought everyone was doing the same mod as Hunday did in Pleiades link, where you just put the single wide bearing in.
I can see how the two bearings would fail.
Good luck finding a new swing arm and new hub... Hopefully a few wrecks around.
Matt.