Hi everyone hope you're all good, just wondering as to the specific parts you need to turn a bike into a paralever, I know basically I will need to replace the gearbox with a k1100 or k100 16v gearbox, and I know I will need to do the same with the final drive however would I need to do the same with the swing arm and drive shaft currently on the bike or would they be able to work with those two other parts?

Off the top of my head, I think you will need a transmission and a complete swing arm with drive shaft and trailing link.  I may be wrong, but I think the Paralever bikes had a different length rear shock as well.

Read this page of my blog:  https://k75retro.blogspot.com/2013/09/paralever-conversion.html

Ask me questions as I've done this conversion.  Swingarm and drive shaft will have to swap as well as the final drive.  You might be able to keep your existing transmission if it's a later model which has the parallel arm ears (no year and model of bike in your signature so I can't be certain).  There will be no holes but those are relatively easy to drill.

It helps to consider a K1100RS front end after doing the Paralever back end. The P/lever is about 50mm longer than a Monolever so you'll be adding wheelbase to an already long girl, hence, slower steering. The K11 forks with triple trees make the wheelbase closer to original and retain reasonably good steering rake/trail numbers. While there, use the wheels from a K11, then the brakes & master cylinder from a K11will be a nice addition. Hell, add the K11 throttle bodies and you'll have....oh, never mind. Just buy a K11

Its a 1987 so I think I'd be too early to not have to change the gearbox, I could potentially do different things later anyway so does anyone know if the 3 spoke wider wheels will fit onto the normal k100 rear final drive it should right?

Depends on the size of tire you intend to fit and the ability to add a second spacer without affecting tracking.  Refer to this document, a collection of forum posts and articles about K1100 and K1200 wheels : https://docs.google.com/document/d/0B3UPbNZRyr1reDNoZFZPcGlHa00/edit?usp=sharing&ouid=103651284721697278882&resourcekey=0-CAMLf_MMynNxfR6xPrXDhw&rtpof=true&sd=true


As far as the pre-provisioned ears that can be modified to mount the paralever, see the circled part on this diagram:

is the reason for changing the transmission purely down the control rod end, if its just the bracket i can fab one up rather than changing the transmission. or is to to do with ratio's? it says in this thread that output driveshafts are all the same so could you just change the driveshaft end for a 16 spline paralever end?
ming

There's no ratio differences. You can machine the gearbox case if it has the bracket to fit the paralever rod on.

Note that you will also need the paralever footrest plates -at least the right one, the OEM one will not clear the extra width of the arm at the rear pivot.

if you need one i have one here inc the rear wheel

jbt wrote:There's no ratio differences. You can machine the gearbox case if it has the bracket to fit the paralever rod on.

Note that you will also need the paralever footrest plates -at least the right one, the OEM one will not clear the extra width of the arm at the rear pivot.

The early transmissions don't have those tangs hanging down. On transmissions that do have them then yes, you can machine those holes. I haven't done it but I know that Special K Larry has done it.

You don't really NEED the paralever peg plates that are stepped out at the rear. You can angle the peg plates out at the rear by adding some washers underneath under the rear peg plate bolts to get the needed clearance at the paralever hump.

The Paralever adds 37mm to the wheelbase over the monolever. As mentioned, bikes with paralevers have a frame with a slightly steeper head angle (about 1', from memory) and, whether it was BMW's intention or not, this will slightly offset the increase in wheelbase.
One of the factors for the long wheelbase is BMW's choice of a short trail. Which might have been to quicken up the steering on a necessarily long, in-line engined bike. The short trail was achieved by using yokes with a large offset (56mm). You can, therefore, reduce the wheelbase of your project by replacing these with yokes with a more 'normal' offest, around 35mm or so. And, this might not increase your trail so much if, as many custom builders do, you jack up the rear end/lwere the front (and steepen the steering angle). Bear in mind that shorter offset yokes mean that you will reduce steering lock as the fork tubes will strike the tank earlier. This will be significantly compounded (to the point of unrideability in car parks) if you end up fitting upside down forks with he-man stanchions, as many custom builders do. A partial solution is to move the tank rearwards.
The lugs for the Paralever torque arm are part of the gearbox casing. You could make an adaptor bracket as the 4 x M10 centrestand mounting holes are nearby, but it'd be fugly. Just buy a lugged gearbox. I've also done this and it's straightforward, but you have to carefully open out the gap between the lugs as well as drilling the holes, because none of the machining is done on the gearboxes on non-Paralever bikes.
The Paralever swingarm offers more tyre clearance than the Monolever, so you can go for a wider rear wheel without having to offset the wheel to the left as you would with a Monolever. I think the Monolever takes up to a 140 section tyre before spacers are necessary to offset the wheel to the left. I've squeezed a 170 section tyre onto a Paralever with just 2mm left offset, no spacers. I machined the swingarm pivots in order to achieve this. You will read all sorts of different offset figures and results from different builders who have trodden the Wider Back Wheel route, so these are just my own measurements, from my own projects.

thank you for all this infomation, its very helpfull, i'm looking to fit a gs 1150 paralever as i want to mount a centrally mounted shock as on the gs rather than the rear mounted diff shock. is the gs paralever the same width as the monolever? or will it require machining to fit?
thanks for all your comments
ming

A 1150/1100 swingarm certainly fits the steel-framed K-series gearbox mountings. But (actually BUT) a swingarm from an R-series is very much longer than a swingarm from a K. This is because the boxer engine/gearbox is very much shorter than the in-line K and the boxer swingarms can be much longer (which improves handling). You'd end up with a long old bike, imagine the Titanic with wheels instead of funnels.
If you search this forum for the build thread for 'K75kforkurz', stuff about R-series swingarms on a k is at post #17. You might find that helpful. Swapping bits and pieces is very much a BMW owners' pastime, so there's plenty of information available. Just keep asking.

Suzi Q wrote:The Paralever swingarm offers more tyre clearance than the Monolever, so you can go for a wider rear wheel without having to offset the wheel to the left as you would with a Monolever. I think the Monolever takes up to a 140 section tyre before spacers are necessary to offset the wheel to the left.

You can go wider than 140. I have 150/70-17 radials on all of my monolever Ks with only the one usual stock spacer.