sprocket carrier bearing mod
 

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

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 ??

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.

The double bearing mod is fraught with danger....In my opinion, too much metal needs to be removed from the hub to allow the second bearing to fit.....The main damage however, is usually caused when drifting in the two bearings...One tap too many, or too hard may crack the shoulder from hub, and then it is only a matter of time before the hub finally collapses.

I searched long and hard, for what I considered a suitable bearing for this modification, and finally came across a NSK double row "Angular Contact Bearing", one that I considered to be perfect for this application.

In the pic below, the original bearing is on the left and the NSK bearing on the right.

http://i233.photobucket.com/albums/e...nnett/cush.jpg

The NSK bearing has an overall width of 22.2mm, requiring 7.2mm to be machined from the hub and spacer bush. As opposed to to the 15mm required, if you are going to fit two bearings.

Provided the hub is set up accurately in the lathe, boring to the required debth is relatively straight forward. Just take it slow and steady, with regular checks of the debth of cut using vernier callipers.

It is also highly recommended that the boring bar tool tip is slightly radiused so that you do not end up with a sharp edge transition at the end of the cut....


http://i233.photobucket.com/albums/e...t/Cush%203.jpg


http://i233.photobucket.com/albums/e...t/Cush%202.jpg


As can be seen in the last pic, there is still plenty of "meat" left in the hub, to support the bearing.

I have done over 20,000Ks on this mod without any problems....(still on the same set of PU cush rubbers).

NOTE: This post has been edited to reflect the fact that I used a NSK bearing...not SKF, as originally posted.

SKF bearing number is?

Skickat fr�n min SM-G903F via Tapatalk

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.

Macca, so Hunday(Andy)'s mod is unlikely to cause this failure? I am poised to do this mod when I return from rotation in the Congo! Andy offers a hub swap out service for local 660 riders. Luckily we are in the same city.
How much play at the hub will indicate OEM Cush rubbers are shot?? Any pointers as I don't seem to have much play yet...
Thanks
Graeme

In Australia I am sure that there are lots of double bearing mods done as this is what is pushed by bike workshops...

Sent from my GT-I9305 using Tapatalk

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?

Professionally, in a Workshop.

Sent from my GT-I9100 using Tapatalk

As far as I know heaps have had it done it, mine has been in for about 20 000km of abuse!! Even Teknik Motorsport in Aust does it as a professional warranted install so they mustnt have had any problems.

I was just really shocked as I read all the posts about it and had never heard anyone machining out to fit TWO bearings...just fitting a SINGLE double row bearing as a replacement. This only requires about 5-7 mm to be removed from the housing and the spacer.

Matt.

According to my SKF bearing book it's listed as a 3304...
20mm ID / 52mm OD / 22.2mm wide...

73304 what I would have thought it would have been..
7 = anglar contact...



..

I have just edited my original post, as I had originally stated that I had used a SKF bearing, but on double checking, it turns out that I used a NSK Bearing.

The specification on box

NSK

3304B-2RSRTNG N

YRLN5

305

Someone correct me if I'm wrong but I think there has been a case or 2 of sprocket carriers breaking up that were still original without being modified ? Which might suggest a dodgy batch of parts similar to a few cases of gear selector problems ?

Just ringing around wreckers & have been told of a few sad stories of single standard bearing issues leaving people strandard and few options but to put the bike on a trailer.

Sent from my GT-I9305 using Tapatalk

Hello, Just to update on the bearing modification that failed for me causing my rear sprocket hub & swingarm to be servery damaged. I have just replaced the hub & swingarm & done some measurements on the hub if you do the double bearing mod you will only have 2.5mm of aluminum left to keep your bearings in place (17.5mm - 15mm for the second bearing = 2.5mm). The double row 22mm wide bearing (3304 2RS) would leave 7.5mm of material.
If you have done the double bearing mod I would be checking to see if there are any signs of fatigue & seriously consider fitting an internal cir-clip as I did as temporary repair to my damaged hub. the cir-clip is a 54 mm bore "D1300-0540". I went to 54mm rather than 52mm because just after where the cir-clip is installed the size of the bore in the hub increases so it suits better.
You can see the piece that fractured off the hub in the second picture.

Hi There, I bought a Xt660z that has the double bearing mod.
The bearing is now rooted and I want to replace the bearing with the same but having trouble finding it at the bearing shop - just confirming the bearing # NSK SM-G903F ?

Ta

Hello Ballylurgan,
Check out the 3 previous pages as there is all of the info that you require, And don't forget to check the 2.5mm lip that double bearings seat against for any cracking that is also mentioned previously.