V7 850 u-joint interchangeable?

[duncan]

This definitely must have come up before, but I cannot seem to find it. I need to replace the U-Joint on my 850GT, it is beyond repair and run out. But which one to get as a replacement?

Currently, it has the old "small" joint with the 20x44mm crosses (12328000), and 28x58x16 support bearing. I can get this one new but it is not cheap.
There is also the larger "new model" joint with the 22x50mm crosses (30328030), which uses a 30x62x16 support bearing. This one is a lot cheaper to buy.

But will it fit?

Both joints are 120mm long, and 61mm outer diameter. Both joints have a 10-tooth spline. Getting a non-standard support bearing sized 30x58x16 is easy...

Surely someone must have tried this ? Even Guzziology makes no note on whether this is possible or not

[fotoguzzi]

is the larger one the same as newer models? ('98EV) I have a good used one I'd send you to try before you buy new..

[duncan]

According to the parts references they are the same, however I suppose the postage costs to get it halfway around the world twice (I'm Europe based) would offset the benefit! Maybe as an intermediate solution you could measure the spline size? The V7 spline is 16mm inside, 20mm outside, and sticks into the join about 30mm.

[Antietam Classic Cycle]

I don't know of anyone that has tried it, but it's a great idea. I see the 30 x 58 x 16 bearing is listed as a wheel bearing for a BMW 320i - should be plenty robust enough to do the job. If you end up doing it, let us know how it turns out.

[John A]

I think the housing for the joint fouls up the joint at extension or compression of the swingarm if I remember but am not sure but something to check out before you spend much

[acogoff]

   Yup, I think you will find that the newer joint is a bit longer and a no go.

[duncan]

Well this weekend I sourced a modern U-Joint to compare to the old style one.

Long story short: no easy swap possible.

Fitting the new model U-Joint to the old gearbox makes it about 10mm too long on the bearing support side.  So, unless we find a 6mm wide support bearing , this won't be easy. Interesting enough, the new model does "hinge" on the same position as the old, even though it's longer center to center: It sits a few millimeter closer to the gearbox when mounted, so it could work.

Now to see how easy it would be to adapt either the swingarm or the U-Joint itself, but that brings this idea well out of "simple swap" area, and into "not worth it" territory. Still, it's interesting enough to go and find out.

Photos make the differences easy to spot. New model U-Joint on the left & top, old model on the right & bottom.

[Antietam Classic Cycle]

You can have the original rebuilt for $140 by John Chicoine here in the US. Shipping might cost a bit though.