13 tooth front sprocket

[Cardinal Direction]

I don't have experience with this product on the CT125, but there is a speedometer "healer"/corrector available which is meant to work with the stock meter, as an alternative to riding with a skewed speed or switching to an entire aftermarket speedometer that lets you program in the correction.

OPMID : Dr. Speed Vehicle Speed Signal Correction Kit [M1403]

Sorry dumb question would this product also keep the abs from flashing and the mileage would also be accurately reflected?

 

[dmonkey]

Looking at the manual and that's exactly what it claims, it connects between the crankcase vehicle speed sensor and the ABS modulator, so it manipulates the sensor reading by whatever % you configure it for and that reading is what's sent to the ABS (which compares it to the front wheel speed sensor), as well as sending that manipulated reading to the meter.

https://opmid.co.jp/wp-content/uploads/M1403.pdf

It also says that if you did just have the OPMID Multimeter to replace the stock meter, changing the speed reading there only occurs at the meter and does not correct the reading from the speed sensor to the ABS - meaning that the OPMID Multimeter screen alone cannot fix the ABS issue with changed sprockets. That part I did not know, I expected that the OPMID Multimeter was also wired up to lie to the ABS.

 

[m in sc]

i had a speedo healer on my grom when i changed gearing, it does exactly what it says it does, changes the signal pulse from the sensor in the motor to the ecm/gauges.

pretty easy and straight forward, def recommend when sticking w a stock gauge or with abs concerns.

 

[Cpd419]

Mine hasn’t flashed-yet.

 

[TRF90]

Strange. Mine has flashed occasionally going fast or slowly with both the 14 tooth and the 13 tooth.

 

[PeteFinVA]

Sadly, the odometer is run by a signal from the transmission. So the 13 tooth sprocket does throw things off. With the 241s being a bit larger, that does compensate a little. My speedometer error is 8 to 10 percent. With the 241s, your front fender will need a lift. But the 241s do not cancel the benefit of the 13 tooth sprocket.

with a 39 tooth rear sprocket, changing a 14 to 13 up front should be a 7.2% difference (so 45mph actual would read 48.5 on the speedometer). I have no idea of the difference in tire sizes but am going to guess it isn't as significant as the sprocket change, so maybe 45mph would read 48. Is that enough of a difference to cause ABS problems?

How much lift is needed to accommodate the 241 tire? I think I saw a post by Dmonkey that drilling four new holes in the fender was enough. Making brackets to lift the fender an inch or so (like the aftermarket kits I see on ebay) seems excessive and it looks to me like there will be contact with the shock boots that would abrade them pretty fast.

 

[dmonkey]

From the various threads on the 13T sprocket it sounds like that change is right on the border of what triggers ABS faults for some CT125s and not others.

No fender lift is needed for the Shinko SR241 tire in 2.75-17. Riding off-road, especially with knobbies, causes more debris to be picked up into the fender. Raising it reduces rock scrape as well as mud & snow pack in the fender, but those aren't going to be an issue for everyone and you could certainly just live with them if it didn't bother you.

 

[AZ7000']

No fender lift is needed for the Shinko SR241 tire in 2.75-17.

Or the 244 with the 3.0-17. I drilled holes because the tire would grab gravel and it would scrape the inside. Raising the fender then removing the horn bracket was free and less then an hour.

So, for those technical folks, bigger tires and a 13t, do they counter each other or does the 13 read higher then add the tires and they too read higher??? Maybe I don't need to do anything!!

 

[TRF90]

Well, there's one complicating factor, and one very easy solution. The complicating factor is that the stock set up is already a bit optimistic. So it's not just a straight mathematical calculation. But the easy solution is to get a GPS-based speedometer app on your cell phone and do a little experimentation yourself. Each bike, gearing, and tire combination is going to be a little different.

 

[koons]

Well, there's one complicating factor, and one very easy solution. The complicating factor is that the stock set up is already a bit optimistic. So it's not just a straight mathematical calculation. But the easy solution is to get a GPS-based speedometer app on your cell phone and do a little experimentation yourself. Each bike, gearing, and tire combination is going to be a little different.

Makes perfect sense. If only there was a simple and accurate tachometer.

 

[NMCoyote]

Going to a smaller (lower geared) front sprocket then adding taller tires cancels out the benefit of the 13 tooth sprocket. Just sayin!

 

[AZ7000']

Going to a smaller (lower geared) front sprocket then adding taller tires cancels out the benefit of the 13 tooth sprocket. Just sayin!

Or does it bring it back to oem characteristics with bigger tires??? So a benefit one could perceive…

 

[NMCoyote]

When going to larger tires, you should always re-gear to maintain drivability. I was just saying you would lose the lower gearing aspect with larger tires

 

[Plotus]

I had learned from my teens that going down on a front sprockets teeth isnot a good idea. The reason is the radius the whip around on it's return dirrection is tighter designing both stress on the links from the increased force exerted by the sprocket 'easier acceleration' and the sharp change of dirrection left or right momentum. Where the larger front is beneficial, is adding teeth to the rear sprocket. It will provide an easier travel through the teeth sizes than the Sharp angle of a 13 tooth. This is how I understood it from early on.

 

[m in sc]

you arent wrong, its better for chain life to increase the rear sprocket size. you want it to be as 'round' a path as possible.