CB650F Sprocket Change vs Odometer

[darkes]

Hi guys,

I'm planning to change both sprockets from stock to 16T/40T and I'm wondering how the bike's odometer gets the speed reading...is it from ABS sensor located on a front wheel or of a transmission. I guess the question is do I need a speedohealer to make needed adjustment and have it calibrated properly or really no need for that if reading is got from an ABS sensor. Thanks

 

[miweber929]

You will need a speedo healer, the bike uses the crankshaft for speed readings since there are two versions.

 

[Enrico]

Hi guys,

I'm planning to change both sprockets from stock to 16T/40T and I'm wondering how the bike's odometer gets the speed reading...is it from ABS sensor located on a front wheel or of a transmission. I guess the question is do I need a speedohealer to make needed adjustment and have it calibrated properly or really no need for that if reading is got from an ABS sensor. Thanks

Excuse my ignorance but what will that do , make it higher or lower geared ?

 

[darkes]

Excuse my ignorance but what will that do , make it higher or lower geared ?

It is going to make it higher/tall geared since stock is 15T/42T

 

[miweber929]

It is going to make it higher/tall geared since stock is 15T/42T

MUCH taller, it's like taking 5 or 6 teeth out the rear. In may opinion the bike will be a slow mess that will struggle to accelerate from a stop, I'd think

 

[darkes]

Well I see your point since 1 extra teeth at front sprocket is like 3 less at back but according to a math numbers are telling me it will lose 10% on acceleration and rpm will drop for around 600 rpm in average. 16T/40T setup is certainly not a final decision and I'll run it by Honda mechanics in my local dealership before give it a go. Worst case scenario I can always revert back to 15T stock front sprocket since I want to keep rear custom made (aluminum with steel teeth).

 

[miweber929]

Well I see your point since 1 extra teeth at front sprocket is like 3 less at back but according to a math numbers are telling me it will lose 10% on acceleration and rpm will drop for around 600 rpm in average. 16T/40T setup is certainly not a final decision and I'll run it by Honda mechanics in my local dealership before give it a go. Worst case scenario I can always revert back to 15T stock front sprocket since I want to keep rear custom made (aluminum with steel teeth).

What are you hoping to do with that low of gearing?

Link to a gearing calculator if you don't have it already:

https://www.gearingcommander.com

 

[darkes]

T

What are you hoping to do with that low of gearing?

Link to a gearing calculator if you don't have it already:

https://www.gearingcommander.com

Thanks Mike, I got it already. I'm not an aggressive driver in the city so I'm fine with losing bit of an acceleration and torque in order to get some lower rpms to get better fuel economy for highway travel. Sure, change will bring more top speed but that was not my goal....This change together with using aluminum rear sprocket and going to 520 chain setup should do the trick as it will take away almost a pound of weight. Maybe one tooth on each end will be sufficient....

 

[miweber929]

Thanks Mike, I got it already. I'm not an aggressive driver in the city so I'm fine with losing bit of an acceleration and torque in order to get some lower rpms to get better fuel economy for highway travel. Sure, change will bring more top speed but that was not my goal....This change together with using aluminum rear sprocket and going to 520 chain setup should do the trick as it will take away almost a pound of weight. Maybe one tooth on each end will be sufficient....

Cool, good luck!!!

 

[Cbat]

Correct me if I'm wrong, you are losing approximately 11% torque each gear (1 - GR2.5/GR2.8). Leaving 15T and going with 40T on back may be a 'better' compromise.

 

[darkes]

Correct me if I'm wrong, you are losing approximately 11% torque each gear (1 - GR2.5/GR2.8). Leaving 15T and going with 40T on back may be a 'better' compromise.

I hear you. Thanks for an advice....After all the calculations I believe you are right.

 

[zulhairii]

why not try F16t and R42t. I done dyno and i lost about 2Nm torque but gain my final acceleration up to 11800 rpm. Also my top speed increased about 5% more form 15t42t stup

 

[darkes]

why not try F16t and R42t. I done dyno and i lost about 2Nm torque but gain my final acceleration up to 11800 rpm. Also my top speed increased about 5% more form 15t42t stup

That’s exactly what I ended up doing and I’m loving it. Also, just to inform everybody how Speedohealer was not needed as odometer reads the speed from front wheel ABS.

 

[EuroBadger]

Also, just to inform everybody how Speedohealer was not needed as odometer reads the speed from front wheel ABS.

Real $hit? Is it just CB650F or does it apply to all other 650s as well?

 

[Victoria]

That’s exactly what I ended up doing and I’m loving it. Also, just to inform everybody how Speedohealer was not needed as odometer reads the speed from front wheel ABS.

I realize this is from a while back now; but is this true? I changed out my chain and sprockets but have yet to ride and was wondering if I needed to adjust for the difference in teeth of the front sprocket.

 

[miweber929]

I realize this is from a while back now; but is this true? I changed out my chain and sprockets but have yet to ride and was wondering if I needed to adjust for the difference in teeth of the front sprocket.

You can verify with a GPS or an app on your phone but I do not believe Honda grabs speed from the speed sensor on the non-abs models and the ABS sensor on the ABS ones, especially on the older, first gen models. That would be a lot of programming differences without much reward so I doubt it.

I looked up parts on the microfiche and came up with 37700-MJE-D01 as the part number for the speed sensor on the ‘16 ABS CBR650F and non ABS 650 (along with a bunch of other bikes including the R models) so it is a commonly used part.

 

[xorbe]

Put the bike on front/rear stands with the engine idling in N. Spin each the tires and see if the speedo shows a few mph for one of them, then you know it's coming off the abs ring and not transmission. I think .... hmm, I could be wrong about the rear tire, I guess that would spin part of the transmission too. Okay, take the chain off too ... 😁

 

[Atucker]

Agree with miweber929. I couldn't imagine why Honda would have a speed sensor and not use it for the speedometer on the ABS version only. However, I would love to know for certain. I have non-ABS and had to buy the Speedohealer when I changed the gearing. I had hopes that I wouldn't need it and could live with the minor inaccuracy from going 14/43, but it was so wildly off that the Speedohealer was an absolute necessity.

 

[Victoria]

You can verify with a GPS or an app on your phone but I do not believe Honda grabs speed from the speed sensor on the non-abs models and the ABS sensor on the ABS ones, especially on the older, first gen models. That would be a lot of programming differences without much reward so I doubt it.

I looked up parts on the microfiche and came up with 37700-MJE-D01 as the part number for the speed sensor on the ‘16 ABS CBR650F and non ABS 650 (along with a bunch of other bikes including the R models) so it is a commonly used part.

Thanks for the response. I'll try verifying with gps/app as you suggested whenever it warms up.

 

[Atucker]

Thanks for the response. I'll try verifying with gps/app as you suggested whenever it warms up.

What gearing did you go with?