Bigger sprockets with the same ratio?

[Guest Krzysztof]

NC700 has super small front sprocket similar to 125cc bikes. 

I think that this small sprocket that wears very quick is also the main cause of short chain life. 

Bikes with bigger front sprockets seems to better on chains. 

 

 

So is it possible to get bigger sprockets and remain the same ratio and keep speedo accurate?

 

[Tex 36,817]

I have no idea if such sprockets are available. You're going to need to research the subject thoroughly. To work out the overall gear ratio you divide "driven by driver". So, if (for example) you have a 17 tooth front sprocket and a 38 tooth rear, it would be 38 divided by 17 = 2.23 :1.

Now if you want to fit (say) a 20 tooth front sprocket you will need to establish the following..

Is such a sprocket available? Or can a specialist make one for you? Also is there enough room in the sprocket housing to accommodate the bigger one?

You then need to work out your rear sprocket size (in this case a 44 tooth rear sprocket would (when used with a 20 tooth front) give you 2.2 :1 so close enough. Can you buy (or have made) a 44T rear?

Oh, and you're going to need a longer chain too. So it would be most cost effective if you wait until your existing chain and sprockets are worn out. Good luck, let us know how you get on.

Edited June 12, 2016 by Tex

[TheEnglishman 401]

In this case, sprocket size has nothing to do with chain life. The London bike couriers I talk to have plenty of gripes with the NC700 but chain life isn't one of them.

I'd look at other factors like alignment and lubrication if your chains aren't lasting.

[DaveM59 1,605]

This is something I had thought about too. As long as the tooth pitch remains the same you wouldn't need to change the rear but the chain would need more links by exactly how many more teeth there are on the new front sprocket and it would lower the gearing but on such a low revving motor that shouldn't be a problem. It will increase fuel use to a similar ratio, again no big deal. The problem is the space in the front sprocket housing is limited and the diameter increase to add only 2 or 3 teeth would be quite a lot. I doubt it would clear. Plus the chain guide on the swing arm would need altering as the chain top run would be higher. More work and trouble than it's worth I think.

[Guest Krzysztof]

More work and trouble than it's worth I think.

 

 

That's exactly what I've thought.

My recent OEM chain lasted for 23K miles and It could last for at least 10K more but the front sprocket was completely hooked. 

I think that I will simply replace front sprocket in few thousand miles and see how it will work out. Rear sprocket shows almost no wear comparing to the front one.

 

I hope that my next chain will last 40K and I know people who achieve that (not NC700 owners).

[bazza 3,629]

NC700 has super small front sprocket similar to 125cc bikes. 

I think that this small sprocket that wears very quick is also the main cause of short chain life. 

Bikes with bigger front sprockets seems to better on chains. 

 

 

So is it possible to get bigger sprockets and remain the same ratio and keep speedo accurate?

sprockets and chains should be changed together - and rear wheel ones can be got in steel or alloy. By the time you have gone to all the trouble and cost I dont think it would be a viable exercise -unless your existing ones are knackered already! Do as Tex says if you do want to do it!

[Guest bonekicker]

Wasn't there something about the speedo not working correctly--if you put a larger sprocket on the front--or as it got nothing at all to do with it?? or maybe dreamt it--yes probably 

[Spindizzy 7,109]

Wasn't there something about the speedo not working correctly--if you put a larger sprocket on the front--or as it got nothing at all to do with it?? or maybe dreamt it--yes probably 

As long as the ratios the same, the speedo would be accurate.

 

Front sprocket generally wears out first if it's the same material as the back, as its doing more than twice as much work. I think, unless I dreamed that as well.

[Guest bonekicker]

Well Spindizzy there's a lot of weird dreams floating about these days--best to keep your bedroom window closed --in case one of they floats in 

[bazza 3,629]

any forum members fitted that belt drive conversion we saw -i think from either Spain or Portugal?

[Spindizzy 7,109]

This one

 

http://www.mmm3moto.com.br/d/honda/kit-relacao-transmissao-secundaria-c-correia-dentada-motocicleta-honda-nc750encomenda.aspx

 

Not much to see on the site

[Defender 3,837]

That explains a lot!

[kayz1 2,928]

I can not see that working on the NC range of bikes, it has the wrong type of bearings and housings so would not take the stresses imposed by a very tight belt.

Only my take on it some one may have different ideas.

Lyn.

[Guest Krzysztof]

sprockets and chains should be changed together

I've heard from few people that it's a myth.

One mechanic I know says there is nothing wrong in replacing front sprocket early if it's wear more than the rest. He get 40K out of his chain on an old CB500.

Few people I know personally (from my facebook) change front sprocket alone without any problems.

[Normsthename 91]

I believe that the 750 Integra has one extra tooth on the gearbox sprocket so that would fit (If I'am right......)

A general rule of thumb is one tooth extra on the front sprocket equals two teeth less on the rear Sprocket and vice versa.

Andy

[bazza 3,629]

Wasn't there something about the speedo not working correctly--if you put a larger sprocket on the front--or as it got nothing at all to do with it?? or maybe dreamt it--yes probably 

Isn't the speedo take off done on the front wheel? Probably wrong but cant see how sprockets would affect that?

[DaveM59 1,605]

The speedo measures wheel rotation which equates to circumference and so distance covered. Changing the gearing between engine and wheel doesn't alter this. Changing tyres might, or even pressures, but it's tiny and insignificant.

 

The number of teeth on either sprocket is also irrelevant as long as the pitch between them is identical. The pitch multiplied by the number of teeth dictates the diameter and the difference in diameters dictates the gear ratio. To maintain the same wheelbase and rear wheel adjustment distance, more teeth on either gear will require a higher number of links in the chain.

[Guest Hati]

The Integra has no pickup on the front wheel. Only the ABS sensor. Same as the rear. I thought the pickup is from the gearbox on the NC bikes, electronically.

[Guest Krzysztof]

Yes. Changing just one sprocket size makes the speedo inaccurate. NC doesn't read speed from wheels.

[DaveM59 1,605]

That's weird, the manual calls the front sensor a 'speed sensor' and the rear an 'ABS sensor' so I assumed the front one doubled up somehow. Ignore the first bit on my earlier post.

This is a bit of a daft design as you can clock up miles on the odometer just by running it in gear on the centre stand, so an unscrupulous mechanic could tell you 'yes mate, took it for a 20 mile run and it was perfect' when all they really did was run it on the stand in the workshop for an hour or so.

This may also explain the weird non linear inaccuracy of speed indication as you set off during acceleration. The reading is only close to accurate at steady speeds and slow increase or decrease when the display updates in single digits. On initial launch it's way out displaying 10mph before you are even at slow walking pace. If the sensor is on the sprocket shaft the revolutions and therefore the pulses will be a lot higher frequency than those sent from a 17" wheel so deciphering these into a digital readout without a lot of processing power will be error prone when the rate is not constant.

 

Testing this theory out, something struck me regarding the DCT faults when bikes get stuck in gear 'get you home' fail same mode. When on the centre stand you can rev it and it will not change up. How does it know you aren't really moving? The only combination of sensors that could detect this is the dual ABS ring detectors so is this sensory movement detection what fails when the gearbox sticks?

Edited June 13, 2016 by DaveM59

[Guest phantom309]

as in another discusion, if you have a DCT you can't change the sprocket sizes ..as it confuses the computer an you will be hitting the rev limiter ...everything has to be as honda made it for the computer to run smoothly...

[Guest Krzysztof]

When on the centre stand you can rev it and it will not change up. How does it know you aren't really moving? The only combination of sensors that could detect this is the dual ABS ring detectors so is this sensory movement detection what fails when the gearbox sticks?

Stand switch won't let you change from neutral.

I also wonder why honda decided that NC should read speed from gearbox/front sprocket.

[Tex 36,817]

There isn't a switch on the centre stand. I'm pretty sure it won't change up because it recognises the bike isn't moving because the front ABS sensor tells it. In other words, it thinks you're doing a huge wheelie!