yellow speedo box

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OB_VegasDude

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I did my speedo box but now have changed my front sprocket to a 16, can anyone give me the correct ratio that figures the stock speedo error coupled with adding a 16 tooth sprocket? I have to wait till next weekend to do it from scratch and cant wait.
 
Hey now, that's easy calculus.

Front 16 instead of 17 means indicated speed changing to 17/16 of previous indication, so 6.25% high.
 
Depends on how your new 16 tooth picks up the speedo. My 16 tooth resulted in an error increase of only 1.5% at 100 mph despite the 6% undergearing.

It's a Sunstar sprocket part #51116.

I have verified this error correction on 2 Busas with the same sprocket...Malcolm's and mine.

If you have the same sprocket Vegas, start with 1.5% and verify your GPS.
 
Whoa! It is a simple calculation, we even have an on-line calculator on our web page;
http://www.ezy.net.au/~fastvid

Going from a 17t front to a 16t front will ALWAYS make the speedo read 6.25% (1.0625 ratio) faster at every speed.

I spent a bit of time last year hooking my Suzuki speedo unit up to our test bench. The Suzuki speedo is VERY linear, so the above statement holds true at any speed.

For D.Pete, are you sure you didn't have any tyre type/size change or other factor in your measurement? How did you measure your original speed error??
 
99TLR,
Thanks for stepping in there, almost couldn't hold back any longer regarding DP's statements.
Must be some magic there?
 
I have to make a comment here.
The stock front sprocket does NOT give any signals to the speedometer. Its a pice that U put outside of the sprocket with four nobs on it that gives the pulses to the pick up.
SO when U changes the sprocket U will ALWAYS have 4 pulses per revolution of the output-shaft.
 
99TLR and others; Member Malcolm and I rode our Busas beside each other when he had a Sunstar 16 and I was stock. We then had the same tires (OE) on the rear.

I settled in at 100 kph (62.5 mph, not 100 mph as I stated above - that was a typo) and Malcolm rode right beside me matching my speed precisely.

My speedo read 100 kph. His read 101.5 kph.

If it is not true that the Sunstar sprocket's configuration alters the pick-up's signal frequency somewhat downward compared to the stock sprocket thereby causing a speedo error increase of less than the sprocket's 6.25% ratio change, then the only explanation I can see is that Malcolm's Busa and mine have very divergent built-in speedo errors.

BTW 99TLR I'm surprised to hear you say that Zook speedos are very linear. You said some time ago on this board that the Busa's speedo error is a variable error of between 5% and 8% (I think those were the figures you used) that increases with speed.

If you are now saying that the error remains constant/linear all speeds, then I have given Vegas bad advice by suggesting he calibrate his Yellow Box for accuracy in a certain speed range. Not that that advice would affect him negatively...if I'm wrong it just means Vegas' speedo is now accurate at ALL speeds.

My question for you is this: If we calibrate your Yellow box for maximum accuracy at one speed, will it then maintain its accuracy at all other speeds?

Thanx for the clarifications. It is not my intent to mislead this board with sloppy testing or erroneous interpretations of the results.
 
I also was under the impression that the speedo changed and gave another busa owner that info. Would appeciate clarification if not true. Thanks
 
Jack, tyre growth would effectively make the gearing taller causing the speedo to under read not over, I'm sure a generous tyre growth figure is probably designed into the calibration for standard speedos, as traditionally they tend to over read more the faster you go, although according to TLR99 not on the Busa which is a surprise given Suzuki's history having Speedos as optimistic as Fords!!!

Where can you get a Yellow box in the U.K. is there a website anywhere?
 
99tlr, i was fiquring a 10% error before the sprocket change. Now i have changed the sprocket to the 16 tooth. Now do I add the two together for a 16.25% error to fiqure in the proper ratio. I would divide 16.25 by 10 =1.625.......is that right or should I set the yellow box to zero then take a gps and go 100 on the gps and see what my speedo reads?

[This message has been edited by VegasDude (edited 26 January 2000).]
 
I understood that the speedo is accurate and that any difference in readings were from tire growth at higher speeds. The tire growth would not show up if speedo is tested on a work bench. Is this correct?
 
Once again: The sprocket does NOT deliver the pulses to the speed sensor. Go to FIG.28 in the Suzuki Parts Catalogue. There is the drawing of Part 34981-42E00 ( Speed Rotor ) this is a rotor that you fasten outside of the sprocket using one bolt through it and into the output shaft. This rotor is made with four-4- "nobs" on it. Every time the outputshaft does one-1- revolution the speed-sensor ( part 34990-33E00 ) picks up four-4- pulses. You can change your sprocket as much as you like but as long as the speed rotor is made with 4 nobs it still gives four pulses.
Now maybye the sunstar sprocket has a different speed rotor with it ( VERY UNLIKELY )( and it has to be a separate part because its mounted AFTER you have put the sprocket and the sprocket nut on the output shaft ) but you can only go from 4 to 3 or 5 nobs. Havent seen any rotors that have 3,5 nobs ( hehehe :) ).
Well This was not a flame to anyone. just facts.
Well over to my cheep speedofix I have talked about before that noone saw ( exept KawAbuser).
The speed rotor gives 4 pulses every rotation of the output-shaft. Thats 9,41 pulses for every rotation of the rear wheel. ( 40/17= 2,35 times does the utput- shaft rotates for every rotation of the rear wheel. = 2,35*4= 9,41 )
So if we move the speed sensor to the rear ( or front ) wheel we can put "nobs" there for the speed sensor to pick up and make pulses off. Well since we cant use 9,41 nobs we have to use 9 ones. Those nobs can be anything made of iron, ie: maybye some nice bolts fastened to the rear-sprocket. When we put 9 instead of 9,41 the speed sensor now pics up only 96% of the pulses it used to do. ( 9/9,41= 0,956= 96% ) and 4% lower reading on the speedometer will be the result.
And testing has shown me the my orginal speedometer only show about 5% to much. So by doing this I get one speedometer thats within 1% accurate and now I can change the sprocket as much as I like without having to readjust anything.
End of topic from my side.
:)
 
Yngve,
Close ... but no cigar!
Your solution will be darn good as long as you leave sprockets, rear-wheel and -tire stock.
But ... as soon as you change any of these you're back to the original problem again.
Let's assume e.g. sprocket change to 17/44 which changes your 2.35 ratio to something like 2.59 multiply by 4 gives 10.36 which makes 10 pulses the closest real option so you will have to add a nice bolt to the 9 already there to give 10/10.36 is 96.6% so
3.4% low reading which again almost cancels out stock deviation.
There really is no EASY/CHEAP solution to changes in sprocket-ratio or wheel/tire-size changes effecting speedo-indication.
Let's put it differently, although by no means for free (unless you were Beta-tester) the YellowBox is still the only real solution out there IMHO and worth its weight
in gold (it's not that heavy is it?)!
 
Animal: I am not only close but I also hold the cigar.....
Read my post CAREFULLY and then U will se that U can change sprocets as much as U want as long as U have the 9 "nobs" ( bolts or otherwise ) on the rear sprocket. And as far as tiregrowth different tire and rear-wheel, who are going to put something else than a 17*6 incher on the rear ? And Those who wants to do so can buy a yellow box. I just provide a CHEAP solution that takes care of 99% of the needs here.
 
And one more thing Animal. when U put the sensor on the rear wheel its the TRUE speed the speedo is reading. When the sensor is at the front sprocket its a factor of the true and the gearing ( 17/40 ) But when I move the sensor to the rear U can have 45/15 in gearing . The rear wheel still moves at the same pace. U see ? Please dont correct me again or I loose every ounce of confidence in U :) ( heheheh )
 
Yngve, the only thing I can say is the YB is in production and is relatively cheap and a simple installation (soon to be easier with "plug and play" connectors).

Your idea is a nice simple solution, why dont mfg's use your aproach?
 
KawAbuser: Remember the old air cooled GPZ?
They had the pick up from the front wheel. I guss the makers of bikes dont give a s.h.i.t. ( I hate it when I have to do that ) about changing sprockets and they just wants the pick up to be as close to the ECU as possible.
And by the way. Do U still need the diameter of the fork? I have been a bad boy and not measured it yet. U see... I hmm.. and there was the story of... and kremt.. ACHIII OK?
I still got the fors in the trunk of my car, ready to ship them to England for titanium-nitrite coating but I havent got any replys from them about the price of the job. And I havent used my car for 3 weeks.
 
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