Custom Cush Drive For Vfr800-Vfr400 Axle !

OK so I modified a VFR400 axle to fit the VFR800 to allow me to fit a BST RC45 Carbon single nut rear wheel, all good there. But I had to fit the VFR400 sprocket carrier inside out to get the correct chain run, as per pic below. It worked OK, but test rides showed that at low revs the power pulses from the engine caused a power pulse vibration which was a pain, and to change the sprocket I would have to undo the axle nut & take the carrier off ! So the grey matter was put to work to come up with an answer !



Ducati cush drives are quite nice, but are of a smaller diameter where it mates to the axle splines, so could not be used, but might be a good base for some measurements, so I bought a secondhand 748 sprocket & cush drive. This was based on the fact that the 916/996 use the same 5 cush rubber unit & they make big power pulses compared the VFR800's 4 cylinder output.

So after due consideration, some measurement & some virtual shopping, I came up with this sketch, the engineering shop got it dirty !



So how do you make this magic thing, well you take one of these original VFR800 inner cush drive parts.



Then get your local engineering shop (SP Engineering in Frome) to make it look like this.







Note the Steel splined centre unit that had the alloy outer cast onto it !


OK, they did the basic turning & drilled/screw cut the 5 cush mounting points to fit with the JT carrier, but I drilled & cut/filed the oblong slots to match the JT carrier profile.

So then take some of these, cut down Ducati cush bobbins



and one of these JT Quick change carriers



Plus one of these



And you get one of these



Add a special one off Ti spacer from the lovely Kayla of ProjectionComponents in the UK & one of her off the shelf VFR400 Ti Axle nuts to complete



And the pile looks like this






The Cush bobbins are loctited in place. The JT carrier has the anti migration lips on the back which now act to hold the carrier in place & the Ti spacer has a 2mm lip to ensure that the carrier can not come off over the nut. I used the original O-ring that would fit in the groove as seen on the inner carrier, trapped between the spacer & the inner carrier to seal the joint against moisture. The indelible marker lines are so I can see if any of the bobins come loose at a later date.

Fitted to the bike it looks like this



Rear view



Much better than before. Only penalty is a little more weight. The VFR400 carrier with sprocket & Ti bolts/SS Nuts was 650grams. New unit with steel splined inner cush & reworked Ti bolts/Alloy nuts is 1,450grams so 800grams heavier, but as I saved 7Kg out of the rear hub & wheel its not a problem. Plus now I can change the sprocket without dismantling the axle.

Enjoy

Chris W.

 

That is more work than I'd ever think of doing to my own bike, but insanely cool. Is this just a one-off, or do you have any plans to try and make a few to sell to fellow riders?

 

Just a one off so that I have a cush drive with the correct chain run for my new rear axle. Looks much better than the Honda one & if I dare to be so bold, is better than the Ducati one, as nothing can migrate towards the swingarm, as happens with their standard sprockets.

 

Well I've put a few test rides on the new cush & its excellent, definately reduces the transmission shock loads, I can hold top gear down to 3000rpm with no dramma & if you crack the throttle open it doesn't act like a jack hammer anymore I need to change down at about 2750 as it gets rough there & that is about the same as the original, so all is good I had to wait to do the test rides, as I needed to drill the axle to allow me to use the Ti nuts holes for a safety clip (hardened steel is a pain to drill, took 2 cobalt drill bits to do it), so I used the clip off the Ducati cush unit I bought to experiment with, fits perfectly.

Onward & upwards more news over the winter as things progress.

 

awesome stuff mohawk!