Sprocket change?

[L.B.S.]

What are the advantages & disadvantages of changing these out?

Very basically, more teeth on the rear sprocket = quicker initial acceleration, and a higher rpm at any given speed. A 45 tooth rear versus a 43 tooth would make the bike a little more "perky" feeling, but also possibly more buzzy at a higher cruising speed, because the engine's spinning higher too.

Going down would have the reverse effect, a more laid back mellow loping lower rpm at highway speed, and more sluggish off the line. Possibly better mpg, but at the expense of performance, and there's the chance of lugging if you are not careful, which can be harder on a motor than spinning higher. (lots of variables here to argue though)

When changing out the front sprocket, it's the opposite; less teeth on the front = more perky, more teeth= more lazy.

Best not to go up or down very much using the front sprocket, as the smaller diameter they get, the harder it is on the teeth and the chain for wear. Too big a sprocket, and it may not fit, or you have rubbing/clearance issues.

Very roughly.

Going down to a 14 tooth from the OEM 15 tooth front sprocket on my CBR125R, upped the perky and the rpm by a lot. 1st gear is so short now, that I have to shift before I get 1/2 way through an intersection. The reason for my change, was to be able to use 6th gear more efficiently.

Stock gearing, the 125R tops out around 120 kph, if it's lucky, on dead flat pavement with no wind. Add a little bit of a slope or headwind, and the rpm drops down low enough to go out of the powerband, and the bike bogs, slows down and you have to then pop down to 5th gear, and scream along at redline, but still under 120 kph.

By going to a smaller sprocket, it raised the rpm enough that 6th gear is now more usable at highway speed of 110-120 kph, and is only doing about 10,000 or 10,500 rpm instead of redlining.

My miles per gallon plummeted to about 80 from 100, doing that.

 

[Beemerphile]

and more sluggish off the line.

I haven't heard anyone say yet that the NC needs to be a little more sluggish. Some gearing thoughts...

1) The tach / speedo readings will not change because the speedo is driven from the transmission. If it said 4,000 rpm at an indicated 70 mph, it will still have this relationship after the gearing change. The difference would be in actual mph vs. RPM. Maybe a speedo healer will come along that works with the NC so that the speedo can be corrected.

2) I concur with Lane's observation that smaller countershaft sprockets speed chain wear and a rear change is healthier for the bike.

3) Top speed may be no better with the taller gearing if the bike lacks the horsepower to redline in top gear. This is probably the case.

4) Remember before adding the 39 tooth rear from the DCT model that it has lower primary gearing to almost exactly offset the lower final gearing.

5) Changing to the 39 tooth sprocket will require two links to be removed from the chain. Likewise a larger rear sprocket may require additional links. Adding links is less straight-forward than removing them. For this reason, an increase in the rear sprocket size would be most economically accomplished at the time the chain is replaced.

6) The DCT model has a 112 link chain and the manual has a 114 link chain.

7) One tool removed from the front sprocket is approximately equal to three teeth added to the rear.

8) Chances are a front sprocket change will not require a chain length adjustment.

 

[bigjay]

Ok, I'm not a gear head... What did you accomplish, exactly, by changing this out... better MPG's? would this do the same on a 700x dct?

Basically Jay i wanted a bit more oomph coming out of corners (2nd gear was a bit lazy at my weight) and make better use of 6th gear (6th was no good from 110kph and under). Now the bike is a little more happier pulling my weight without labouring the engine. This gearing change will increase torque, reduce top speed and use a tiny bit more fuel. Very hard to notice the difference but its very subtle. As to the 700x DCT, it depends on what u are after. Better fuel economy and less rpm? Then a bigger front/smaller rear is the go. If u want to accelerate quicker then smaller front/bigger rear. A word of warning with 700s owners. Anymore than 2 up in the rear you will run out of room on the swingarm.

 

[L.B.S.]

I haven't heard anyone say yet that the NC needs to be a little more sluggish. Some gearing thoughts...

1) The tach / speedo readings will not change because the speedo is driven from the transmission. If it said 4,000 rpm at an indicated 70 mph, it will still have this relationship after the gearing change. The difference would be in actual mph vs. RPM. Maybe a speedo healer will come along that works with the NC so that the speedo can be corrected.

8) Chances are a front sprocket change will not require a chain length adjustment.

heh heh, I giggled a little bit at the mental picture conjured up of quite a few members here gasping in horror at the idea of lowering the rpm for any reason, but there was at least one or two fellows that mentioned wanting to do this that I've noted back in the dusty past.

Good point about the trans drive speedo/rpm notation- I think all my bikes except my F800 (which took it's speed from the rear wheel sensor ring) have had front hub speedo drives.

 

[Antarius]

I haven't heard anyone say yet that the NC needs to be a little more sluggish. Some gearing thoughts...

1) The tach / speedo readings will not change because the speedo is driven from the transmission. If it said 4,000 rpm at an indicated 70 mph, it will still have this relationship after the gearing change. The difference would be in actual mph vs. RPM. Maybe a speedo healer will come along that works with the NC so that the speedo can be corrected.

2) I concur with Lane's observation that smaller countershaft sprockets speed chain wear and a rear change is healthier for the bike.

3) Top speed may be no better with the taller gearing if the bike lacks the horsepower to redline in top gear. This is probably the case.

4) Remember before adding the 39 tooth rear from the DCT model that it has lower primary gearing to almost exactly offset the lower final gearing.

5) Changing to the 39 tooth sprocket will require two links to be removed from the chain. Likewise a larger rear sprocket may require additional links. Adding links is less straight-forward than removing them. For this reason, an increase in the rear sprocket size would be most economically accomplished at the time the chain is replaced.

6) The DCT model has a 112 link chain and the manual has a 114 link chain.

7) One tool removed from the front sprocket is approximately equal to three teeth added to the rear.

8) Chances are a front sprocket change will not require a chain length adjustment.

A lot, but not all, of this is true.

1) Regardless of what the DCT gets in mileage, a 4 tooth smaller rear sprocket (39 instead of 43) on the standard X will turn less RPM at a given speed than that of a stock 43 tooth rear sprocket. You can calculate the difference, but at 70mph it will be in the neighborhood of 500rpm. Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator will help illustrate that.

2) You are correct in the DCT having a different primary ratio, which is why you can't say "If I put a 39 tooth on my non DCT X it will be the same as a DCT.". It won't. It will be "slower off the line."

3) Regardless if you change a front or rear sprocket, a chain adjustment will likely be needed. You may need to remove a link OR INCREASE THE WHEELBASE if you change the rear sprocket smaller, or do the inverse if you increase the size of the front sprocket. It will depend on the current amount of slack you have (or don't) in your chain as it sits.

In my case, I commute 110 miles a day at 70mph each way. It is worth it to me to reduce my RPM by roughly 500, while still traveling 70mph. Hence, a smaller rear sprocket. I'd prefer to go with a larger front sprocket though, but can't find one.

 

[Beemerphile]

A lot, but not all, of this is true.

1) Regardless of what the DCT gets in mileage, a 4 tooth smaller rear sprocket (39 instead of 43) on the standard X will turn less RPM at a given speed than that of a stock 43 tooth rear sprocket. You can calculate the difference, but at 70mph it will be in the neighborhood of 500rpm. Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator will help illustrate that.

2) You are correct in the DCT having a different primary ratio, which is why you can't say "If I put a 39 tooth on my non DCT X it will be the same as a DCT.". It won't. It will be "slower off the line."

3) Regardless if you change a front or rear sprocket, a chain adjustment will likely be needed. You may need to remove a link OR INCREASE THE WHEELBASE if you change the rear sprocket smaller, or do the inverse if you increase the size of the front sprocket. It will depend on the current amount of slack you have (or don't) in your chain as it sits.

In my case, I commute 110 miles a day at 70mph each way. It is worth it to me to reduce my RPM by roughly 500, while still traveling 70mph. Hence, a smaller rear sprocket. I'd prefer to go with a larger front sprocket though, but can't find one.

What part of what I said is specifically untrue?

1) My first statement said that the indicated speed and RPM would not change with a change of sprockets but that the actual speed to RPM would change. I believe this to be true as the speed sensor is reading from a transmission gear and it has no idea what goes on in the final gearing. It assumes the stock ratios and rear tire rolling diameter. The tach is a pulse counter and though it is an analog bar output, it has a digital (pulse) input.

2) I did not say (nor do I believe) that: "If I put a 39 tooth on my non DCT X it will be the same as a DCT." In fact, my statement implies they will not be the same.

3) I did not say that no chain adjustment would be needed with a front sprocket change, I said that "chances are" no chain length adjustment would be needed. Since it takes three times the rear tooth count change to equal each tooth of front sprocket change, the chain limits will be much more quickly reached with a rear sprocket change. One tooth up or down on the countershaft is a half-link difference in required chain length and most likely the slack adjusters can make it up. Honda uses two more links with the 43 than with the 39. Both the DCT and the manual have 16 tooth countershaft sprockets. The 112/114 link chains give respectively the same range of chain adjustment for both. If you do not change the number of links when you decrease the rear sprocket, you are using up some of the adjustment range. At that point you would have to remove a link to make the stretch adjustment once you hit the rear stops.

I think it most prudent to make the gearing change at the rear and use the correct number of links to retain the full adjustment range.

 

[Antarius]

Your statement regarding the DCT's primary ratio implies that a sprocket change would be null. That's not true. But I may be misunderstanding your post.

Same goes for the chain adjustment, but I see you covered yourself by saying "chances are."

And finally, as a person who has over 100,000 miles under my belt on the street, racing experience and having been fortunate enough to get paid to ride for a living at one point - ill disagree and recommend a front sprocket change (if going up in size) any day of the week over a rear.

 

[Beemerphile]

Your statement regarding the DCT's primary ratio implies that a sprocket change would be null. That's not true. But I may be misunderstanding your post.

Same goes for the chain adjustment, but I see you covered yourself by saying "chances are."

And finally, as a person who has over 100,000 miles under my belt on the street, racing experience and having been fortunate enough to get paid to ride for a living at one point - ill disagree and recommend a front sprocket change (if going up in size) any day of the week over a rear.

Yes you misunderstood. I implied that it would not be null. I said chain length adjustment, not chain adjustment. I did not "cover myself" with "chances are". My agreement with Lane's statement meant I agree with the upper physical limit for fitting under the countershaft cover and the fact that smaller countershaft sprockets are harder on the chain. You are free to keep increasing yours "any day of the week" until it locks up and rips the cover off. Have you had the cover off and do you know how much reserve diameter it has? How close to the chain cover are you willing to run?



And finally, I had 100,000 miles under my belt forty years ago and have racing experience though I never got paid to ride.

I don't know why I bother. Carry on.

 

[Antarius]

Huffy and puffy over a different opinion? Relax . Obviously there's a limit to how big you can go or little, weather you change the front or the rear.

 

[n30r3l0ad3d]

Each rider has a different opinion, and it will vary with every bike and persons riding style. To me, the NC is geared ideal for the best of both worlds. If you want a faster take off at the cost of top speed, gear it up in the rear or down in the front. If you want more top speed at the cost of lugging the motor more, gear it down in the back and up in the front. Down meaning less teeth, up meaning more teeth.

 

[johnakay]

well if us fatty's lose about 28lbs the bike would definitely be faster and you'll feel much healthier to.
see just ask uncle john

 

[Johnny D]

Very basically, more teeth on the rear sprocket = quicker initial acceleration, and a higher rpm at any given speed.

With that in mind, look at the size of THIS sprocket! I Bet this bike took off like a rocket

 

[L.B.S.]

With that in mind, look at the size of THIS sprocket! I Bet this bike took off like a rocket

View attachment 7230

If I'm not mistaken, didn't those (or a variant) come with two sizes of sprockets bolted to the wheel, so one could simply switch from smaller to larger as specific conditions required?


Oh, and with that big 'un, it took off like a rocket...for the first 10 feet, and then hit the rev limiter, I bet, lol

 

[showkey]

If I'm not mistaken, didn't those (or a variant) come with two sizes of sprockets bolted to the wheel, so one could simply switch from smaller to larger as specific conditions required?


Oh, and with that big 'un, it took off like a rocket...for the first 10 feet, and then hit the rev limiter, I bet, lol

Correct two rear sprockets ......later a high/low gear box was added on the trans.............either way low-low is a crawler gear.

 

[pismocycleguy]

I would like to add a one tooth larger front (countershaft) sprocket, or a 2 tooth smaller rear sprocket on my NC700X, but I cannot find a source. Any suggestions where I can find and purchase either, or both, of these sprockets?
Thanks for the help.

 

[StratTuner]

I would like to add a one tooth larger front (countershaft) sprocket, or a 2 tooth smaller rear sprocket on my NC700X, but I cannot find a source. Any suggestions where I can find and purchase either, or both, of these sprockets?
Thanks for the help.

SprocketCenter.com? Chad is there and could know where to order something that fits. He's a good guy.

 

[Bamo]

Just wrote about my new 39 tooth rear sprocket on another thread in the technical section. Instead of going down just two on the rear or trying to find a front in a different size, just order a rear sprocket from Honda for a DCT model. The stock is 43 and the DCT is 39. Makes a big change and I think the bike works great with it. That is the easiest most effective solution in my opinion.

 

[pismocycleguy]

41 tooth rear sprocket

Just wrote about my new 39 tooth rear sprocket on another thread in the technical section. Instead of going down just two on the rear or trying to find a front in a different size, just order a rear sprocket from Honda for a DCT model. The stock is 43 and the DCT is 39. Makes a big change and I think the bike works great with it. That is the easiest most effective solution in my opinion.

Bamo,
How many links did you have to remove from your chain after installing the 39 tooth sprocket? Or did you order a chain when you ordered the sprocket? I'll read your post in the other thread.
I found and ordered a 41 tooth rear sprocket from Sprocket Center today.
I was told it would be at my address in 2 days. I'll let everyone know how this works out.
Thanks for the post.

 

[n30r3l0ad3d]

Going from a 43 tooth in the back to a 39 tooth would make the bike work harder, thus sacrificing acceleration. Might give it better MPG on the highway though.

 

[Bamo]

I had to remove two links. The sprocket was actually a fair amount smaller. As far as the acceleration, like I said in my other post, I felt no real difference in the feel of the pull. It accelerates just as hard if you want it to or you can lug it more and keep the rpm's down easier. I think the torque was under utilized in this bike and I actually feel like it accelerates harder because the torque gets more use and the gear lasts longer. I do not feel like I use the clutch anymore to get the bike going and even with my girlfriend on the back it pulls just as hard at all speeds. Not sure why Honda did not use the 39 to start with but in my opinion it is a great choice for those looking to drop rpm's.