changing the rear end to a paralever

[bmwrusso]

I would like to change the rear end of my r75/5 to a paralaver. I have seen this done but not sure about what years of the R series bikes would work best for the conversion. I have just starting getting into the upgrade of my bike and it came with a modern sport bike front end I would like to keep and change the rear end to match it.

Any info would be appreciated. I have the ability to make adapters, weld new mounts ect... but I am sure there are different swing arms that fit better than others so any info woudl helpme save a few headaches.

[PGlaves]

I have seen it done to a K75 - because a K1100 transmission would bolt up fairly easily.

I can't imagine what transmission would bolt up to an Airhead that would provide a place for the swingarm to mount.

I fairly strongly suspect that pulling this off will cost you a few times more than the bike cost.

But I'm all ears if somebody does know how to do this with some sense of economy.

[20774]

I tracked down some comments made by Snowbum on the Airheads list. He said there's not "that" much different that wouldn't allow such a conversion. I think what he's suggesting is that the swap is from the output of the tranny back. I can't tell from his comments if first you make a swap to the monolever (which is a direct swap it appears) and then perform modifications for the paralever. I don't know these bikes that well to say...

Seems like the issues are the mounting of the single shock...top end up near the tool tray and the bottom end near the rear brake pivot point. Some relocation of bits and pieces is needed. He suggests that more side bracing would be needed similar to what CC Products offer. Probably the front end triple tree would need to be upgraded as well.

[PGlaves]

I tracked down some comments made by Snowbum on the Airheads list. He said there's not "that" much different that wouldn't allow such a conversion. I think what he's suggesting is that the swap is from the output of the tranny back. I can't tell from his comments if first you make a swap to the monolever (which is a direct swap it appears) and then perform modifications for the paralever. I don't know these bikes that well to say...

Seems like the issues are the mounting of the single shock...top end up near the tool tray and the bottom end near the rear brake pivot point. Some relocation of bits and pieces is needed. He suggests that more side bracing would be needed similar to what CC Products offer. Probably the front end triple tree would need to be upgraded as well.

It seems to me the crucial welding/machining/re-engineering comes in when you try to figure out where to swivel the swingarm. Maybe using the original points in the frame work but in OEM fashion the swingarm pivots in the cast rear of the transmission.

Neat idea - I hope somebody has good pictures!!

[R90S]

Whatever for?

[bcgilligan]

Wonder if it might be not be more practical to use an R100R rolling chassis, and drop as many cosmetic and mechanical pieces and parts from your R75 into that frame. That way, you'd already have the rear end issue resolved. I'm certain there'd be lots of other surprises using this approach!

I remember being at the Morganton, NC National in 1995/1996(?), and finding a large crowd of rally goers surrounding an R100RS with Paralever. I believe this had started out as an R100R, then had the RS fuel tank,fairing, and other pieces from the RS installed on it.

Bob

[bmwrusso]

so a monolever would be much easier then? either way I am cool with it. i am just looking to have a bike with 17" wheels front and back. something a little different since i already have the full front end off a gsxr on the bike and this will cost much less than trying to find all the parts to put the bike back to full stock. and then i might not like to look of it.

ill document the entire thing as I go along so others can see the progress.

where were the comments by snowbum and what years of the monolever will fit?

[20774]

where were the comments by snowbum and what years of the monolever will fit?

I went to the archives on the Airheads Beemer Club forum and did a search. I found his thoughts from a number of years ago. IIRC, he said that a monolever (he didn't restrict the year) was a direct swap. Doesn't that make sense? Of course, the early '80s monolever (R80ST, etc.) was basically built on the same twin-shock chassis that were still in production. Seems to me they would be very close.

[The_Veg]

It seems to me the crucial welding/machining/re-engineering comes in when you try to figure out where to swivel the swingarm. Maybe using the original points in the frame work but in OEM fashion the swingarm pivots in the cast rear of the transmission.

Neat idea - I hope somebody has good pictures!!

On the R100R/GS/M the swingarm pivots are in the frame (and look a lot like non-paralever pivots but I cannot say with authority if they are indeed the same), and the transmission is the same as with monolever bikes of similar vintage.

[The_Veg]

Wonder if it might be not be more practical to use an R100R rolling chassis, and drop as many cosmetic and mechanical pieces and parts from your R75 into that frame. That way, you'd already have the rear end issue resolved. I'm certain there'd be lots of other surprises using this approach!

I remember being at the Morganton, NC National in 1995/1996(?), and finding a large crowd of rally goers surrounding an R100RS with Paralever. I believe this had started out as an R100R, then had the RS fuel tank,fairing, and other pieces from the RS installed on it.

Bob

Just keep in mind that the R100R/GS/M use a different frame than other airheads. It is similar, but slightly smaller and things may not mount quite the same.

[bmwrusso]

is the k frame much different where the swing arm mounts? i was looking at k parts as well for the conversion. they seem to be more readily available.

[The_Veg]

is the k frame much different where the swing arm mounts? i was looking at k parts as well for the conversion. they seem to be more readily available.

The swingarm mounts to the transmission on the K, as Paul mentioned above.

Another factor to consider is the mounting-point of the rear coil/shock unit. On the R100R/GS/M, the lower mount is to the final drive- but on most other models it mounts to the swingarm. I don't know how interchangeable the shick-units are in mix-match applications as the length would be different between the FD-mounted ones and the swingarm-mounted ones.
As for the upper mount, the R/GS/M had the upper shock-mount on the upper-rear part of the 'loop' of the main frame. If you tried to modify a different frame to accept the paralever, this big mounting lug would have to be welded on and you might then have to do some subframe mods to accommodate.