Tonti u-joint carrier bearing mod

[leroy_can]

  Hi, This is light years from being a new topic but just thought I would show my solution. Keep in mind that it is yet to be determined if this has weakened the swing arm significantly but I have a pretty good judgement on such things and feel it will be alright. If someone feels it will fail all I can say is time will tell. The slot in the swing arm could be top or bottom and could be strengthened by welding in  a .100-125" thick slotted patch I would say 1/4-3/8" larger in all directions. The reinforcing patch would of course make it trickier to get snap ring pliers in but I'm sure it is doable.
      I have had my LMIV engine/trans split a half dozen times for various reasons #1 would be clutch spline replacement. The first time or 2 the u-joint stayed with the swing arm but since it has always been loose and twice has had the famous 6 piece inner race even though it has never had roughness or vibration. I have tried LPS rapid steel,Loctite 271, and Locktite 680.I always thought the










high resolution photos
next disassembly would be a problem but  it never has been as nothing has held. As well following the first inner race failure both u-joint and bearing were replaced.
      I did this mod so I could assemble the bearing to the u-joint out of the swing arm. This time as always my u-joint feels perfect but needs a .003 shim to be a good fit. It was easy to do the  .003" shim and 680 Locktite out of the swing arm. Doing the shim and locktite with the bearing in the swing arm would be hopeless.
       My solution is a 3/8" wide slot 1.4" long as shown. I started at 5/16" but had to keep expanding it and experimenting with different snap ring pliers until I could reliably get the snap ring in and out.
      MOST IMPORTANT!!! On assembly the snap ring must be in place before you put the bearing on
      Then I made a installation tool much like you would use for normal u-joint installing Steel 4" long 2.685" O.D. 2.335 I.D.
      This tool is now pushing on the relaxed snap ring and easily pushes the bearing perfectly flush where it is stopped by the expanded snap ring.
      Now that the bearing is in that far and pretty well guaranteed straight you can easily work around the outer race with a skinny punch simply rotating the gap on the clip to access the race.
      2ND. MOST IMPORTANT!!! if you drive the bearing in all the way now the snap ring is blocked by the knuckle of the u-joint and can't be compressed enough to get in.
       Solution is only push the race in far enough to expose the start of the snap ring groove and now it is easy to compress the ring and start it into place. It should stay put when released and then finally tap around more with a punch now pushing on the snap ring and it will pop into the groove nicely.
       Disassembly should be the reverse where you would get the ring up out of the groove and then let the bearing push it the rest of the way out. I am happy for now and didn't try disassembling it but not concerned of course you could also push the u-joint out of the bearing and take the bearing out normally.
       I intend to cover the open slot with electrical tape or similar and back it up with a hose clamp. Should almost be unnoticeable on the bike.

[fotoguzzi]

 

[Don G]

Why not retain the bearing with a set screw like on the EV's?   DonG

[leroy_can]

  Hi, Not sure of how that is done on the bike you refer to but the point of this is getting a good fit between the inner race and the u-joint which I feel can be done best out of the swing arm. I can't imagine how a set screw could be utilized  to secure those 2 parts. I don't know if heat from spinning in the race causes them to crack or it is from the flopping about from the looseness but a cracked inner race on carrier bearings seems very common and could lead to catastrophic failure.

[Don G]

The bearing is retained in the swing arm by a set screw, no snap ring involved, so instead of cutting a slot to access the snap ring, throw the snap ring away and modify the swing arm to accept a retaining screw. Carry on with the bearing fit though....  DonG

[leroy_can]

 Hi, I did a bunch of searching and can't see for sure how they did that. Mostly looking at ebay photos where of course nobody is trying to show the set screw. One shot looked like possibly a very long screw angling in from the front outboard. I can see that as being a good solution if I am seeing it right. While googling I came across Guzzipower's reinforced swing arm. Seeing how much they felt it necessary to ad makes me 2nd guess my slot but I'm not racing.

[jacksonracingcomau]

Don’t know how to find it but someone posted pic on here of how last cali’s did it (5 years ago ?)
I copied same on mine then ————using grub screws instead of circlip
When you see it , it’s so obvious you wonder why Carcano didn’t do it in 1965
Or myself in the 35+ years before I did

[leroy_can]

  Very much appreciate the input from both Don G  and Jackson racing. Definitely a "why didn't I think of that" moment. Too much focus on how I could manage to do the snap ring instead of thinking of alternate means of bearing retention. 1 or 2 set screws would be the best way to do this for sure and would not be difficult at all. 

[acogoff]

     One thing I have found is the recess for the carrier bearing is slightly out of round, probably from the welding process, at least on the ones I checked. Thus when bearing and u-joint assembly is pounded in it tends to put a bit of squeeze on the outer race causing a slight binding with the balls using a standard clearance bearing. Could be the cause of the u-joint tending to spin. The use of a C3 clearance carrier bearing is what has worked for me to prevent this happening.

[Rough Edge racing]

 By out off round do you mean .0005 inch?....In my opinion, using a C3 bearing  in an out of round housing not the best...If the housing is more rigid that the bearing outer race, you will have an out of round bearing race...

[John A]

On the swing arm of the Cal series , ‘88 up to when they used the set screw, you can assemble the snap ring and bearing on the joint, then after installing it there is room to set the snap ring with a couple screwdrivers alongside the ujoint. Only works on the Tonti’s with a big ujoint cavity.