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Offline kaitoro

  • Inazuma Junior
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  • Bike: Red Inazuma
  • City / Town: Auckland
  • Country: New Zealand
Re: Gearing
« Reply #7 on: June 17, 2013, 06:26:09 AM »
 :002: You can actually take off in first gear (if you're careful) with NO throttle and the bike will idle along at 7 kph showing on the speedo. If you want to go slower than that you would need to slip the clutch. You can also do the same (if you're REALLY CAREFUL) in 2nd and it will cruise at 10-11 kph with no throttle. It does baulk a bit in 3rd!

Offline Robell

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Re: Gearing
« Reply #8 on: June 17, 2013, 08:53:31 PM »
Got as far as taking the front sprocket off this evening, to check a few dimensions.

It took an impact wrench to get the nut off  ! :232:
The only other issue is that the speed sensor is driven off the end of the output shaft, which means, if I'm thinking straight, that if you change the sprockets, the speedo won't give a correct reading.

The DRZ400 looks to be a good match, it's a little wider, don't think that would be a problem.
" it's better to burn out, than to fade away "

Offline kaitoro

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Re: Gearing
« Reply #9 on: June 18, 2013, 01:17:40 AM »
My GPS (Garmin etrex 30 Handheld) reads 5% higher for km travelled than the speedo; I presume therefore the speedo is now reading 5% low for kph. I don't know what the difference was before changing the sprocket. 

Offline Robell

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Re: Gearing
« Reply #10 on: June 18, 2013, 07:21:42 PM »
Ordered a sprocket today, a TU250, which looks to be the same dimensions, but the width is closer to the Inazuma than the DR.
It was only £7 + postage, so not much to lose, if I've got it wrong.


I don't have GPS, I might try a cycle computer to get a comparison, if it'll register high enough :008:

" it's better to burn out, than to fade away "

Offline Robell

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Re: Gearing
« Reply #11 on: July 01, 2013, 08:46:26 PM »
Well, I've finally got there, 15 tooth sprocket fitted on the front.

This is what I've done :

The standard sprocket is 14 tooth and is 8.5 mm wide.
Unfortunately I couldn't find a diect replacement.
The DRZ400 sprocket is 10 mm wide and the TU250 sprocket is only 7 mm
Also, the teeth are central on the Inazuma sprocket whereas both the above are offset, with a flange.
After some careful measurement, I've fitted the 7 mm, TU 250 sprocket, with the flange at the back, this should mean the teeth are lined up as per the original.
Because the new sprocket is narrower than the original, I've made up a new washer (0.100" thick) to fit under the retaining nut, as the nut wouldn't tighten on the std washer.

As I thought, the speed sensor  relies on the gearbox output shaft, so the speedo reading is unchanged despite the different gear.
To get some idea, I rigged up a Cateye cycle computer to compare against the Suzuki speedo.
(Obviously I can't be sure how accurate this is)
On the standard gearing, compared to the Cateye, the original speedo over reads by almost exactly 10%.
With the new sprocket fitted the Cateye and Suzuki speedos are within 1 mph of each other.
So, either the speedo is now more accurate than before - or - it now under reads by about 10%  :001:

Maybe at this point I should say that this is clearly not an approved modification. If anyone wants to folow what I've done, fine, but don't hold me liable  :002:
The sprocket I've used is from JT sprockets part no JTF434.15
I also pulled a favour, to get the new washer ground to the correct thickness.
Other than that it's an easy enough job for anyone with a decent toolkit, including torque wrenches and an impact driver, to get the sprocket nut undone.

All I have to do now, is go out and test it :002:
" it's better to burn out, than to fade away "

Offline Robell

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Re: Gearing
« Reply #12 on: July 02, 2013, 09:51:43 AM »
Update :

Ridden the bike into work today. The most noticeable difference is in 1st gear. On standard gearing I found you need to change up into 2nd almost immediately. With the new ratio, 1st is a much more useable gear.

 A downside is that the mile counter is now under reading. My commute is normally 17 miles, today the same route is only 16 miles !
I guess the mile counter works from a combination of the gear selected and the speed sensor. As I've raised the gearing, the counter is now getting altered messages - tho judging from the speed tests I did, it might be more accurate now than before !

I'll keep the updates coming :002:

" it's better to burn out, than to fade away "

Offline scoot

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Re: Gearing
« Reply #13 on: July 02, 2013, 11:41:43 AM »
Nice one Rob will that give a better top end speed??
Scoot  :152:
Adventure...BEFORE... Dementia

 


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