Swing arm mod that works.

Well, having had all the oil fall out of the gearbox through the rear oil seal (ha,ha) recently, I've had cause to strip the thing down AGAIN!!!
Took the shaft out for inspection and, after 20000 miles since I "mono-shocked" the swingarm, there is still some drag in all the bearings. So the mod appears to be having the desired effect.

Howard,
please explain why this improves life of the output shaft seal.

In words of no more than two sillyballs of course!

i don't think it does. i think it may prolong the life of the shaft.

I'm trying to figure this out.

Am I correct in the following statements/observations?

The paralever design seems to have problems when used on the GS. The GS has more suspension travel but crucially has more ground clearance - so both universal joints run at more of an angle than on say an RS or on bikes belonging to heavy riders (or so I've heard).
It would be better for any UJ to run straight through (less sideways 'push' on the bearings). Sorry for the non technical speak!
Howards modification locks the second UJ in such a position. But it's my understanding that it's the UJ at the gearbox that takes the worst battering.

Perhaps by locking the second UJ it forces the shaft to run at lesser angle through the gearbox UJ? I've just been sketching this out and it seems to be the case. But the angle difference doesn't seem to be that great. There is probably less length change to the shaft aswell.

Howard does your bike now behave as a pre paralever G/S ? - the back end rising on acceleration?

How have BWM solved the problem on the new 4 valvers? (Er, I've just realised they're not new anymore !) Have they just 'beefed' things up or worked out a proper solution?

Questions, questions..... and from me with a chain and sprockets (that'll last longer than a paralever shaft!)

Driveshaft problems.

IMHO the first reason for the early paralevers shaft weakness is the fact that BMW moved from oiled joints to dry ones, that couldn't stand the stress as well as the original monolever.
The concept of transfering the propulsion torque back to the chassis was and is valid and works, the evidence you can see everyday in all big BMW's today.

Universal joints of the kind used by BMW produce cycles of accelerations and deccelerations which stress them more than just the torque that drives throgh them. However, when the setup is like what we find in paralever BMW's, the output shaft and bevel shaft more or less parralel, the two joints theoreticaly cancel each other cycle, if constructed in the correct way.

The bigger the angle the joints have to work with the bigger the stress, thats why as you wrote, road paralever holds better over time. Also, offroading can put the joints through sever cycles of great torque used by rider, something non existent on the road (the lower the gearing the greater the torque that goes through to the wheel.

That's why, I think, modified shafts with grease nipples are much more reliable, just becaus one has a way to insert grease into the shity bearings every once in a while.

On my bike, the previous owner improvised with a joint from a little Fiat, I have no idea who did it for him, but it is still running fine.

Lastly, I'm sure Howard's bike behaves like a monolever, the torque produced pushes the wheel down as in any old Beemer, or Guzzi.

Miky

The first post was a bit short and unexplained because just as I got to that stage my dinner was ready.

Anyway. The shaft now runs at a lesser angle. The rear bearing should ( in theory) never wear out because it is running straight. UJs wear out faster the bigger the angle they run through. The front bearing runs at a shallower angle and thus should last longer as well.
Bear in mind here that I've never had a shaft last beyond 25K miles.
I don't know what shaft life is on the oil heads but I believe the bearings are a lot larger. Not only that but the design was changed so that the splined slide is in the middle section. The slide is at the bevel box end on mine which, theory has it, puts an extra strain on the lower bearing.

Yes it does rise and fall with the throttle. Not, however, as much as I had expected. This could be down to having a decent rear shock (Ohlins) with decent damping. I've had several shaft drive Yamahas (XS750, XJ650 & XJ900) and it is about the same as them.

In answer to Spouts last comment about chains. My Tiger955i is now on 17000 miles and the chain, with Scottoiler, is probably only 25% used. So I expect it to last longer than any of my drive shafts when using the Paralever. And it will be cheaper to replace.

Hmm gerabox oilseals eh ! Hope you manage to get yours sorted for your trip to Corsica - we got there, but not back - said oilseal blew - bugger.
Still like to have a neb at that mod, if (and it's a big if) we get to the Kent do, and you are, will have to have a closer look.
Hope your trip goes there and back

bad luck Fritz mate

will catch up with you at some point re Corsica - want to do a route of mediterranean islands next year.

bob

but do you use your tiger off road howard?

Spout said:

Howard,
please explain why this improves life of the output shaft seal.

In words of no more than two sillyballs of course!

Click to expand...

Sorry I missed this question.
Answer :- it has no effect on the life of the output shaft oil seal.
Mine failed (probably) because it was fitted by a BMW dealer clown!!

cookie said:

but do you use your tiger off road howard?

Click to expand...

Yes.


I've ridden some green lanes in France during the summer. Dry & grassy, fast & gravelly. It handles pretty well. The forks impressed me. Miles better than my old 100GS. Also the new 955i engine has a lot of torque low down. So it pulls hard from tick over without the shuddering of the boxer.




But not in the really serious shit yet. It's too new and shiney and expensive at the moment. When it's out of warranty and has a few scratches on it, I'm mad enough to try some TCK80s on it.