If the slipper fits.

You already know what's coming but I can promise you this will be 'wheely' good...

 If you read the previous blog entry about slotting the CBR600 F3 front end on: you will have already seen the above image giving you the shocking sneak preview that I intended to fit a CBR600 F3 rear wheel to the VFR750 too!
The 18" OEM wheel shares the same spindle size, making this mod fairly easy.
This was dropped out and sold on then slotted into the back of the VFR.
It is very nearly as simple as that. The chain lines up nicely with the original left spacer leaving only the right side spacing and the rear brake caliper to sort for a really straight forward mod.
Of course it could not be that simple and straight forward or the forums wouldn't be full of unanswered questions and half assed descriptions of other peoples solutions.

The back brake

The simplest answer is to reduce the size of the VFR's caliper bracket so it can line up with the CBR600 wheels smaller disk. This can be achieved by either cutting it down and welding or by replacing it with a CBR600 F1 bracket which is a straight swap and mounts the same caliper in the right place.
The next answer would be to use the CBR600 F3 rear caliper that I already had from the downer bike and married up to the disk nicely as they had been traveling buddies for some miles already.
The main draw back of this is that the caliper bracket's guide tab is designed to run in a bracket on top of the CBR's steel swing arm; which is normally hidden under a plastic cover. I could reproduce this on the VFR but it was going to be ugly at best.

Of course during my time reading up on possible solutions; I had to look at what the VFR750 6x actually ran. The under-slung twin piston caliper on the right is very reminiscent of the rear brake setup on my RD250 which I made last year. This would be easy to replicate on the bigger bike and would still provide ample stopping power when coupled with the four strokes much stronger engine braking.
I had the spare red caliper lying around so I checked it had enough bite to take the wider CBR disk; of which it swallowed with no difficulty at all.This would work just great! All I would need is a tab welding underneath the swingarm, then a tie bar and bracket making up to look like the same light weight solution pieced together in the HRC workshops all those years ago.
However if I was going to weld a tab on the swingarm, would it not make sense to replace the swing arm with something that looked more authentic also?
A CBR600 F4 runs a very similar looking swingarm to the 6x's RS derived HRC item (which fits with a little coaxing) and even came with the backup plan of running an F4 caliper bracket should I run out of time to build the under slung setup.
All of the parts here were coming up VERY cheap and the work required to fit them was not out of my reach, but I was too aware of the fact that I was building two race bikes this winter and I needed to be realistic with my plans.

I instead decided to go for a less destructive solution where the F3 caliper bracket is drilled and tapped to take the VFR's stay bar.
I say less destructive but 30 years of road salt had already beaten someones attempt to free the rear bolt which was well and truely rounded. Th threads were soaked with penetrating oil and a slot was cut into its head with the view of replacing the bolt on removal but even the impact drivers bit just bent. Finally a steel bar was welded to the bolt head which with a groan finally relented.
 Annoyingly the bolt has a huge shoulder on it to support the stay bar so I ended up needing to reuse it. Thankfully the weld rebuilt up a couple of flats so a socket could be tapped on and the bolt was usable again if a little ugly.
 The bracket and stay bar were reassembled on the motorcycle.
The front stay bar bolt was back at home although Christ knows what I did with the nut which is M10 1.25 (fine) so a new one of those was quickly ordered. The rear bolt screwed into its new home nicely although proved a little long which was quickly sorted with a bench grinder.
It will not be possible to torque the rear mounting bolt but wire locking will take care of that for as long as this thing will remain on this motorcycle.
A wirelocking hole was achieved by making use of the slot I had cut into the head of the bolt previously.
I first lay wire welded the top of the bolt back flat then tidied it up with a second wider pass to smooth things off.
The remainder of the slot was now a great guide for a small drill bit to make short work of making a hole for wire locking.
Save for a quick tidy up on the grinder to bring the flats back, this bolt was back to new[ish].
The bolt could now be tightly wire locked onto the tie bar to prevent it from vibrating loose which could be mildly dangerous.

Spacing

Now I had a final solution (for the time being at least) for the rear brake, I could get on with making a spacer to tke up the slack in the back end.
I opted for the quick and dirty option of taking the CBR's spacer and grinding off a couple of mm's on the new 8" bench grinder in my shed.
This did the trick just great meaning I now had a fully rolling VFR on 17"wheels.
Save for the far too small sprocket, this bike is essentially rideable. With the front end dropped thanks to the shorter forks, the back end will only need to be jacked up a little to allow for the half inch drop in wheel height.
Yes the new spacer is an absolute ass pain to fit and the rear brake set up it not the prettiest; but it is not intended to be this way for long.
I fully intend to go for the CBR600 F4 swing arm swap and under-slung caliper but for now, this will get the bike on the track.
To finish the build I chucked a set of new EBC HH sintered bronze pads in all of the calipers along with a full bleed with fresh Dot 4 to ensure the bike will stop as well as I hope it will go.
Things are are really starting to come along for the VFR build. Some foot pegs would be nice mind....