Should I change gearing on Gixer 750 K5

blackninja

blackninja

blackninja

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13 Nov 2007
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Bike has stock engine with stock gearing and I am thinking of going -1 up front .. in this shot I still had a bit of fifth and sixth to go as I eased the throttle so I should be able to get away with -1 on the front .. Is there a better option? How accurate is the speedo anyways at those speeds??

speed001.jpg
 
I doubt you'll see the top speed of your bike on anything but the longest straights.

Oh and worst I've just been to Le Mans shots I've seen so far this year :p
 
Speedo is massively out at those speeds, mine was showing almost 165 when I was doing just over 150, until I got a speedo healer, then it does not matter at all what you do to the gearing :p
I personally went +2 on the rear and loved it, still had a decent top end and acceleration was improved.
 
Took me well over a mile to reach top speed of 165 at Bruntingthorpe 2mile straight on my ZX9R (showing 185 on the clocks lol). May a well go for faster acceleration for road and normal track use :)
 
Just gone 1 down on mine. Makes such a difference on the road. Speedo on mine is around 10mph out at 70mph. SpeedoHealer will fix this.
 
would it not be better to go up on the back instead? if your speedo runs fromt he front sprocket then change the back and your speed will still be accurate
 
I've recently done -1 on front and +2 on rear to my srad. acceleration is a bit metal
but i've lost quite a bit top end.

this also put my speedo well out but a speedo healer is worth every penny.

also consider it will slighty effect your mileage counter and fuel consumption....but its a sports bike so who cares :)
 
famas said:
I've recently done -1 on front and +2 on rear to my srad. acceleration is a bit metal
but i've lost quite a bit top end.

this also put my speedo well out but a speedo healer is worth every penny.

also consider it will slighty effect your mileage counter and fuel consumption....but its a sports bike so who cares :)
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Think I'll start with -1 front and see how that feels ... may try +2 on the rear after that ... only for track so the latter is of little concern and it has only done 3300 miles from new :)

Fitted the gilles rearsets yesterday as well ...that'll save me boots!
 
I've gone -1 at the front on my RSV. Thinking of going 1 up at the back too. Speedo isn't taken from either sprocket so not affected by gearing :) .
 
St0rmer66 said:
I've gone -1 at the front on my RSV. Thinking of going 1 up at the back too. Speedo isn't taken from either sprocket so not affected by gearing :) .
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It is mate... think about it, your speed is worked out from rotation over a sensor somewhere in the engine (like end of cam shaft). Due to front sprocket -1 change the rear wheel is moving less distance per revolution of whatever the sensor is measuring.

The only way your speedo wouldn't be affected is if the sensor was on either wheel hub, or you had a built in GPS :)


I'm guessing with -1 front you are reading around 12.5% over what you are really traveling at


edit: I think on my bike the speed sensor is on the engine casing around the front sprocket, and it counts teeth (hall effect), but it's still gonna be wrong as there are less teeth per revolution (it doesnt know there has been a final drive gearing change)
 
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Fireskull said:
Speedo is massively out at those speeds, mine was showing almost 165 when I was doing just over 150, until I got a speedo healer, then it does not matter at all what you do to the gearing :p
I personally went +2 on the rear and loved it, still had a decent top end and acceleration was improved.
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As above, was gonna suggest a speedo healer if your gearing got altered.
:)
 
Fireskull said:
Speedo is massively out at those speeds, mine was showing almost 165 when I was doing just over 150, until I got a speedo healer, then it does not matter at all what you do to the gearing :p
I personally went +2 on the rear and loved it, still had a decent top end and acceleration was improved.
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OK ... got the gearing -1+2 with healer and now showing 146mph @ 12800 rpm in sixth ... anyone calibrated their K5 750 against a gps at this rpm/gear to see what it actually is?

Considering going +3 rear now as I tussled with a K8 600 which had -1/+3 and I had difficulty getting past on the stright .. so with fifth being revved out and sixth @ 12800 where I roll off methinks that -1/+3 will be the sweet spot for Le Mans ... which is where I was the past 2 days :)



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I'm sure there is a mathmatical way of working it out, I just stuck a GPS on tank and rode at 100 indicated, read the gps speed and then worked out the %

Stopped at side of road, dialed in % on speedohealer and repeated and both read the same all the way till 100

It's a bit dodgy doing this though as it's hard to read a GPS boucing around on your tank :)


I wouldn't take gearing any further, -1 +3 is crazy extreme, and you'll and up in a tyre wall or looping the thing off the start
 
Flukester said:
It is mate... think about it, your speed is worked out from rotation over a sensor somewhere in the engine (like end of cam shaft). Due to front sprocket -1 change the rear wheel is moving less distance per revolution of whatever the sensor is measuring.

The only way your speedo wouldn't be affected is if the sensor was on either wheel hub, or you had a built in GPS :)
Click to expand...

The speed sensor is on the rear wheel on the RSV (picks up the rear disc bolt heads) so you can modify the final drive gearing till your hearts content without affecting the speedometer accuracy.
 
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