When I originally started building the Katana, I was set on selling the original clocks, and  buying a digital speedo. I fancied a set of all signing all dancing clocks that as well as providing tacho, and speed could do everything you might want on a bike: lap times. max revs, max speed, acceleration, temperature, make a cup of tea! That sort of thing ;o)

When I saw the original clocks fitted however, and used them for the tacho, I can’t bring myself to swop them out. They are such an iconic design I decided they had to stay. Basic set up is easy as it just plugs into the loom. Once you have sorted which connector goes where, the idiot lights and tacho just work. The speedo however does not. It’s mechanical, and need s a drive from the fornt wheel.

Problem 1

We need a speedo drive that mates to the 25mm spindle of the TL1000s and has the same mechanical pickup of the bandit 1200 wheels.

Simple – start with a bit of internet research – looking at page after page of eBay adverts, build projects, photos, it looked like either a ZX7R, ZXR750, Mito, or Ducati drive might work. However, for a variety of reasons, none of them are an easy fit. Either they drive the wrong way, have a different drive pickup, or would require a custom cable. So I opted for the simple solution.

The bandit wheels have appropriate bearings change to suit the 25mm spindle , and we made spacers to suit – I figured getting a bandit speedo drive bored out to the 25mm spindle diameter would be the easiest option. See my last blog post on that particular epic … but here you go .. bored and none bored side by side.

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Problem 2

The clocks are from a GSX750S Katana … a Japanese import, and read in kmh. With a max of 180kmh. even mating the speedo drive to them will give a max speed read out of 180kmh or 111mph. Mating everything together would give me a working speed in kmh as long as I stayed below 111mph.

Thanks to Neil Ronketti who pointed me in the direction of this little device:

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It takes your mechanical speedo drive input and mechanically converts it to mph on your clocks. So basicaly my kph read out will now be mph read out. With a max read out of 180 we should be fine :o)

It’s not the end of the story of course, as the gearing for the clocks are based on a 19 inch wheel. I have 17 inch wheels so we need to allow for that. I did some calculations. A bike with 17inch front doing 100mph rotates 10.53% more and therefore reads 111.76 mph. We can live with that.

So with the kph clocks having a max of 180 kph on them, we should be good for a true max speed 161 mph – which is fine and dandy!

Problem 3

The TL1000S Spindle has an integral collar one side and on the other side has a thread that mates into a collar that is captive in the fork leg – held in place by the pinch bolts. The original plan to simply machine back the integral collar came to nought, as the spinle is hollow. The hole down the middle of the spindle is actually tapered, meaning by the time we had cut back the collar to allow the drive to fit, we’d have less that a mm thickness in the spindle over about 3mm length – not good for supporting a front wheel!!

Talk turned to making a spindle … then in a moment of rare lucidity it came to me. Simply swop the spindle round, and machine back the captive collar on the other side and have that mate to the speedo drive. Suzuki had in their infinite wisdom also allowed several mm before starting the thread on the inside of the collar  .. so we had space :o)

Thanks to Spike (Cambridge Motorcycles) for his patience yet again. As usual a simple machining exercise truned into a less than simple problem solving exercise.

Problem 4

With the collar machined and speedo drive in place, the wheel was solid on tightening the spindle. A few more measurements deduced that the speedo drive was 2mm shy on the inner bearing – I can only assume we have a drive from a different model, or there is an inner spacer with the original design, so another quick spin of the lathe, and we had a 2mm spacer, and 2mm further off the captive collar, but more importantly, the wheel turned on the bearings.

Job’s a good ‘un.

Back home with everything fitted, and bolted together:

The only issue I now forsee is that the remaining metal on the speedo drive is quite narrow. It seems to be holding up, and has not crushed under the force of the spindle tightening … so I pronounce it a good one until it fails. ;o)

I quick scoot up the road and it’s definitely reading speed 🙂

It’s been a good few weeks working out how to do this  …  but worth it to have the original Kat speedo working – it’s a design classic, and I wanted it to be part of the final bike.

 

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