The SR500 sidecar - repairing the sprocket carrier and converting it to a more conventional style

First of all let me point out that the initial idea for all of this isn't from me, but I gave it my personal touch. The original idea can be found at Motorang's Buchelli Projekt - Kettenblatttraeger  

 

As you can see in this picture, the whole setup on XT500 and SR500 models is a bit on the weird side. In an attempt to save a bearing in the sprocket carrier a very elaborate clamping solution has been employed. This worked so well that on the XT600 models the almost identical rear wheel hub was modified to have a bearing and a spacer be independent from the rear wheel. 

 

Luckily there's enough meat in the sprocket carrier to modify it to accept a 6006-2RS ball bearing instead, as it just has to be bored out to 55mm and 13mm deep. The just part is that you don't really have a clean reference surface, so clocking and tapping it in is the bigger part of the job. 

Aiming for a decent press-fit of 54.95mm, I beautifully overshot the mark and made the almost perfect sliding fit on my very first sprocket carrier. Nothing a bit of bearing glue can't fix though.
 

A few days later there was "a bit" of snow outside the workshop. 

The drawing calls for a 30mm tall spacer, which over a length of 14mm is turned down to 30.00mm and an internal bore for a 17mm axle (i.e. 0.1mm oversized). As my stainless barstock was 55mm that dimension was set as well. 

... and when you nail your dimensions like that, the sprocket carrier is a straight fit.

The big trick here is that the actual spacer protrudes from the bearing by about 1mm.

 

Now whilst the modification of the sprocket carrier was (sort of) normal lathe work and engineering, the modification of the actual rear wheel was a bit more medieval. But let's have the pictures tell their story.

Up to this point this is where I followed the instructions from someone else. Whilst I cursed the 55mm round stock initially, when I had to turn it down to 30mm, it also meant there's an off the shelf seal available in 55x75x10mm and with a recess in the sprocket carrier that's 14mm deep, well it's a match made in heaven or by an engineer. 😎

At this point, swapping the tyre and then fitting the rear wheel should have been a more or less straightforward job... 

Let's just say that the Avon Sidecar tyre lasts a lot longer than is good for the lubrication of the rear wheel axle.

And absolutely no one upset the thread on both the rear wheel axle or nut. Which is also why absolutely no one would know that it is a M16x1.5 thread.

It was at this point that the sins of yesterday started catching up to me:

First, I borrowed the speedo drive from the front wheel for the summer wheel, which I only found out AFTER installation. 

Luckily there's a very straightforward repair kit available and aside from the new seal actually being tight around the speedo drive there weren't any challenges to be overcome.

And then there was this bolt that holds the chainguard onto the swingarm, which after reinstallation reduced the amount of unhealthy noises attributed to the engine significantly. 

So in the end there was only thing left to do:

Interestingly enough the new rear tire appears to be of a slightly smaller circumference, which together with the sprocket carrier not wobbling around and most likely the cold weather favoring my bad habit of jetting slightly on the rich side all in all yielded new top speed records and the little sidecar feels a lot quicker than before. (If you're more into hard facts: I gained more than 10kph in top speed and there was still a bit left.)