39 rear sprocket?

MRCapps

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I just recently bought a 2013 NC700X and love the bike! The previous owner (my Uncle) replaced the rear 43 tooth with a 41 and I can comfortably ride at 75-78 on the interstate. I ride most of my time on the interstate or highways and was thinking of going to a 39 tooth for the rear for passing power at higher speeds. I know the DCT models had a 39 tooth which I am assuming would fit my bike. Has anyone gone with a 39? Opinions? Thanks!
 
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dduelin

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More teeth on the rear is more passing power on the highway. The engine turns higher rpm where it’s making more horsepower. Less teeth On the rear sprocket means the engine turns less rpm for a given mph. The acceleration will tend to be more sluggish with a 39 rear.
 

MRCapps

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Wouldn't the 39 make for more top end though? Like say, i wanted to cruise at 85. Wouldn't the 39 make that work better than the 41? Maybe Im confused...
 

670cc

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Wouldn't the 39 make for more top end though? Like say, i wanted to cruise at 85. Wouldn't the 39 make that work better than the 41? Maybe Im confused...
I’m pretty sure the engine runs out of power before it can pull red line in top gear. (I’ve never tried it). If you try to gear it taller with a smaller rear sprocket, it may be sluggish in sixth gear, causing you to drop to 5th. At that point you aren’t really gaining anything.

In case you didn’t know, the internal transmission gearing is different on the DCT vs the manual, so even with the DCT’s 39 rear sprocket vs the manual’s 43, the overall gearing in 6th gear is nearly the same on both versions.

If your uncle originally had a rear 45, that wasn’t the stock sprocket to begin with. 43 is stock for a manual.

If you do go to a 39 you’ll need to shorten the chain.

If you want low RPM, but less power on the highway, your current 41 tooth might be the best combination. If you need passing power, you need more RPM, and that’s what the gear shift is for.
 
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MRCapps

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I’m pretty sure the engine runs out of power before it can pull red line in top gear. (I’ve never tried it). If you try to gear it taller with a smaller rear sprocket, it may be sluggish in sixth gear, causing you to drop to 5th. At that point you aren’t really gaining anything.

In case you didn’t know, the internal transmission gearing is different on the DCT vs the manual, so even with the DCT’s 39 rear sprocket vs the manual’s 43, the overall gearing in 6th gear is nearly the same on both versions.

If your uncle originally had a rear 45, that wasn’t the stock sprocket to begin with. 43 is stock for a manual.

If you do go to a 39 you’ll need to shorten the chain.

If you want low RPM, but less power on the highway, your current 41 tooth might be the best combination. If you need passing power, you need more RPM, and that’s what the gear shift is for.

I apologize, yes the stock was a 43 and he swapped it for a 41. The reason this all came up is a couple times i hit 85 and it felt like that was really pushing her in 6th so i was wondering if the 39 would allow cruising at 85 to be more comfortable... thanks for the reply and ill edit my original post to show the 43.
 

Bcsmith

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Hmmmm I would not be inclined to change from the original sprocket as Honda has put a lot of engineering into gear ratios. It seems it should be pretty easy to maintain the speeds you are talking. Now I not often get on the freeway but have not had any issues with top end. How is the compression on your bike?
 

dduelin

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In most situations my 700s went as fast in 5th as 6th with stock gearing. DCT and manual. With no wind or a slight tailwind or slightly downhill on the manual it was possible to hit the rev limiter in 5th, 99 or 100 mph, and 6th could add 5 or 6 additional mph but in other situations it couldn’t pull any faster in 6th than 5th. 6th is an overdrive. Like Greg posted, the bike doesn’t have the power to pull a taller gear ratio and increase top speed in 6th.

I never had a problem running 85 in traffic unless a really stiff headwind running up a grade, then I might have to drop into 5th.
 
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Rapturee

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I ride most of my time on the interstate or highways and was thinking of going to a 39 tooth for the rear for passing power at higher speeds.

Hey Capps, I have done the 39T swap and have a lot of experience with it and thousands of miles touring with it. First let me say that i agree fully with 670/Duelin. Secondly, let me make sure i am understanding your question and the basis for it. You stated that you wanted to cruise down the freeway at 80-85mph and were looking for "More Passing Power"....OK.

I believe we'll all agree that the NC700X/NC700XD is nearly out of power at 85mph as that is not what it was designed for with it's given power/torque rpm range. The key to any vehicles real power is to be able to get the engine into the real Power/Torque range and keep it there until the demand for it has ended. So the real passing ability hinges on "YOUR" ability to get the NC into it's useful "powerband" quickly and as needed. So, you can change either of the gears or both of them as well as the rear tire height to attain that needed or required(in your situation) power to pass as you feel is needed for whatever situation you have found yourself requiring.

So, experiment away. Here is a site i enjoy using to plan my changes before i make them. Here you can change your drive gear up or down a tooth, change the rear sprocket up or down, and change the rear tire size up or down and of course any combination thereof.




My experience with the NC began with wanting more mpg. While wanting to squeeze more MPG out of mine as i commuted, that turned into let's see how much i can squeeze out of it. What are the limits of the mileage that the NC can achieve. I fully documented this and the modifications i made to attain each level of achievement on Fuelly.com.

So before changing anything else I started with upping the air pressure in both of the tires. I aired them to 36F/42R and that netted a little bit but really changed the handling for the better.

Next i added 1 tooth on the drive sprocket and went up to a 17T. I really liked the added mileage i gained with it and what felt to me like a small amount of "pulling" power on the freeway. The speed limits in my area are 70mph. So unless i travel over to Montana where it is 80mph that is all i legally get. :{P

As the rear tire became worn out i replaced it and went up to a 150/70-17 which added a little more mpg and what also felt to me like a small amount of added "pulling" power on the freeway when horsing around or simply passing someone.

(let me state here that the mpg increases were real and showed at the pump. The "felt" pulling power was seat of the pants and not measured in any meaningful way other than my perception. I still fully agree with 670/Duelin's prior statements).

About here is where i started using my GPS a lot more for speedo corrections as my speedo was now off enough that it started bothering me. I started touring and taking 500+/- mile one-day rides so i really started burning up the miles on my NC and that rear tire didn't last very long. Wanting to see if i could get even more mpg out of it i changed to a 140/80-17 rear tire and increased the mpg yet again. I was super happy with the mods i had done and the mileage gains i had attained... but i started noticing i was having to down shift two gears now to pass. I also noticed that the NC really liked 3500rpm-5400rpm(IMHO) for passing. That was the approx rpm range that i found passing easy(imho).

Shortly thereafter i grabbed a 39T rear sprocket from another member here and got it installed right away. So now i have the both the 17T/39T sprockets and the 140/80-17" rear tire. This combination netted me a best of 100.6 mpg on my little test track(it's where i take my vehicles(NC) and ride 50 miles out and 50 miles back and check the mileage. It is a beautiful river rd and so very twisty & scenic to ride, so it's a great place to check your modifications. The speed varies from 55mph-35mph as it follows the winding river. I always ride right at the limit or 5mph+ on that road, everytime).

Then what i found is the speedo was almost exactly 20% off. With my new-to-me DCT i find it rides about 3800-4k rpm on the freeway while the manual with those changes was only 3k-3200 rpm. About what i feel a 7th gear would have been. With these changes i also found that i was down shifting 2 gears and sometimes 3 gears just to pass. I quickly adapted to this and it was never a problem for me.

With these mods i also regularly pulled two mountain passes when i travelled. I no longer was able to pull either of them in 6th gear, i had to down shift to 5th to pull the passes. Again i adapted to this change and it was not a problem for me at all. I also felt there were no meaningful changes when i took off from a light or stop sign. The NC has an amazing amount of low-end torque so it just rolls away from a stop. Even when i rode nearly 1800 miles 2-up with about 100lbs of camping gear, taking off was never a problem nor passing 2-up(with all of that same gear) with these mods.

Simply put, IMHO the NC is an incredible machine if you use it as intended, or modify it to your liking to better fit your use/needs! Ride ON!! :{)

The pictures show the 39T mod(i could not find the 17T pic), the 140/80-17 rear tire mod, the "fully loaded" solo ride, 2600 miles, 7 states, one week and the "beyond loaded" haha 2-up ride that was 1776 miles, covering 4 states, all in one week, and was the first time i toured with a pillion.
 

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