OK, so a looong  time ago I bought myself a nice speedo to fit on the handlebars next to the Tach, as you can see in the picture.



The pic was deliberately taken when the odo clocked egg-zactly 55 thousand Km  

So... I unfastened the cable from the tank-mounted speedo, fastened the cable (GT550 tacho cable) of the bar-mounted speedo and away I went into the sunset, happy as a lark right ?

WRONG !

Unfortunately... this speedo underreads by at least 10%...  

I mean, at 4000 rpm the OEM speedo reads 100 Km/h (60mph) whereas this one reads a mere 90Km/h (55mph)

This is definitely no go !

At the moment I have 150790x15 rear tire, which will give a 5% higher final drive ratio; then I fitted chain drive which is 17/49 (=2.88:1) as opposed to the 2.94:1 of the OEM belt drive... which is another 2 % more...

So I already have the bike running at least 7% faster than the tank-mounted speedo will read... (110km/h on gps Vs. 100~105 speedo reading)

I sincerely cannot accept to have a bar mounted speedo reading overall 10-15 % LESS than my true speed ! (and distance... )

Other than "chuck it", any suggestions ?

These things are expensive, they come at around €100 (=$130) here in Italy !  

Have you used a gps to clock your speedo to see how far either one are off?
Did you spin the GT550 by hand before you installed to see if it was turning freely?
And how old is the GT550 cable? (slippage maybe? not sure if a slipping one would give a consistant reading)
Sounds like you took all the ratio's into account, so other than cable problems, I would think it would be the speedo is off.
I used to be a big fan of adjustable gauges and meters, what ever happened to those?

On the other hand, a 160 mph speedo could be converted into a 160 Km/h speedo with a "reduction converter",
basically a "box with gears" where I plug in a cable from the gearbox and another (short) cable which spins 1.6:1, into this 160 mph speedo.

The result would be a 160 Km/h speedo !  

Anybody care to help me out ? I already have the basic project done !

Dave wrote on 01/14/14 at 07:11:48:


Thanks, Dave, this is EXACTLY what I had in mind !



I would use the OEM speedo cable from the gearbox to the adapter, anopther OEM cable from the adapter to the speedo, and
Presto !
160 mph speedo becomes 160 Km/h (100mph) speedo !  

Unfortunately their website seems to be locked, not one link worls...  

I'll try emailing them, see what they suggest  

verslagen1 wrote on 01/14/14 at 09:03:09:


I did the Trailtech Vapor, and it is accurate - but it does not provide the Vintage look that a matched set of gauges hanging on the top fork yoke provides.

I went with the digital route as I have changed my tire size, and am screwing around with the gearing to see what works best for me.  I currently have a 25 tooth Kawasaki EN454 front pulley and a Kawasaki 65 tooth rear pulley from a KZ750.  Not sure what the final set up will be - but I have the potential for 3 different ratios and since I am not changing my front wheel....my speedo stays accurate no matter what I do to the gearing.

The numbers on the sweep tach don't start until 2 thousand and go up to 12 thousand - but there is a digital counter on the bottom right side of the screen for reading the digital rpms so you can accurately see your idle speed.  Also you can program in a yellow shift light for whatever rpm you want, and a red warning light for the max revs.  I believe I have my yellow light set for 5,500 and the red at 6,000....or something like that.  The red lght is not a rev limiter.....so when it lights up you just know that you are over the rpm you have programmed in as a warning.

There is also a recall button so you can see the max rpm, max speed, time on trip, time spent riding, engine temp, etc.  I don't believe the 7,480 rpm shown is accurate - I have to install a little bigger resister in the tach wire, as there is a certain spot in the rpm range where the tach spikes for one breif jump in rpm even though the engine speed stays constant.

Put a shorter rear tire on it?
If its off 10%, & you KNOW its off 10%, then, while it may be irritating, just because its not "right", you know how fast youre going,, Heck, my gas gauge doesnt even MOve for like, 150 miles or so,, then it comes down fast, then hits "The Big E" & it will go another 40 miles or so, its FAR from an accurate gas gauge, but, it gives me enough info that I know what to do.,.& a speedo that actually off a known %age? Hey,, I can do a 10% adjustment in my head. Ive read your posts,,Im thinkin you can too,,

mpescatori wrote on 01/16/14 at 07:10:59:




It is not as nice to know the odometer is underreading by 10%...

Yeaaa,, thats a bit of a bummer, tryin to figure wher that "time to refill" moment is. But, you get to 110 on the Odo, youre at 100..
& the wonky conflict between the tach & speedo? I think that would be the one I disliked the most. Question IZZZ, just how much Munneee is it worth? Those "Impedance matching boxes" with the gears to make iot work out look pricey And, well,, kinda clunky to have in the speedo line..
In recent years Ive been forced to accept things & let things be "Less Than" what I really want, due to health. My makeup, all my life, has been what would easily be called anal.,Id spend hours hiding wires when Id move & set up the stereo. Id spend hours adjusting bearings on the 10 speed. To be fair, it was a very different design, the front sprocket kept spinning even when I stopped pedaling. It would change gears w/o pedaling & had a buncha bearings in places other bikes didnt & they were single, no races,,Anyway, Ive learned to let things go that arent "show stoppers". Im not sure how I feel about it, but Im not seeing any real "loss" by not doing things "To the gnats ass" like I did.
I gotta tell ya, I was always impressed by Diggers pics. His garage was always spotless. Whoda guessed ASStronauts were anal?