Sprocket Swap?

[rickdc]

I see that my 700x dct has a 39t rear sprocket, and the 700x has a 43t. So, if I swap my 39 for a 43, I can assume I'll lose some mileage and top speed, however, I should have more torque in top gear, right? Has anyone tried this? I know, why bother, well, if Honda bumped up the cc's to give it a little more power, why not try what we can do and see what happens?

 

[670cc]

The reason the final drive ratio is different between the DCT and the manual, is the the internal primary drive and transmission gears are different sizes. When's it's all factored in, the two transmissions have nearly the same overall ratio in top gear. Both engines make essentially the same power, too.

If you swap your 39 for a 43, you will need a two link longer chain. It's one thing to take links out but a bit more trouble to add them. Also, I believe the DCT can become unhappy if you modify the gearing too much, since it monitors the speed of the wheels and the transmission shafts.

 

[TigerDude]

why do you need torque in top gear with a dct? The bike downshifts for you.

But yes, you'll have 10% more torque & 10% higher revs

 

[Beemerphile]

I can see this change as beneficial to the NC. In fact, I have a 45 tooth rear waiting to replace the 43 for use at my next chain replacement. I don't like the way the engine feels at low revs under load. If you decide to do this, I have a 43 tooth sprocket in good shape that you can have for postage. As 670cc says, you'll have to solve the chain length riddle though because you will need to increase the chain from 112 to 114 links.

 

[ld_rider]

I should have more torque in top gear, right?

The extra 3 or 4 lb ft of torque should make all the difference in the world....go for it!

;-)

 

[ld_rider]

I don't like the way the engine feels at low revs under load.

Downshift?

 

[Beemerphile]

Downshift?

Yes, I know how to downshift. A vehicle with lower overall gearing has a different character than a vehicle with higher overall gearing in all gears.

 

[ld_rider]

A vehicle with lower overall gearing has a different character than a vehicle with higher overall gearing in all gears.

Lowering the gearing = downshifting...isn't it the same exact thing?
Change the gearing so that you are running the same RPMs in 4th gear as I do in 3th at a given speed....what am I missing?

TIA

 

[showkey]

Also, I believe the DCT can become unhappy if you modify the gearing too much, since it monitors the speed of the wheels and the transmission shafts.

^^^^+2. I believe there is a service bulletin when the DCT released NOT to change the DCT sprocket ratio.???????

 

[bamamate]

Lowering the gearing = downshifting...isn't it the same exact thing?
Change the gearing so that you are running the same RPMs in 4th gear as I do in 3th at a given speed....what am I missing?

TIA

Not necessarily, the jumps between gears, 1-6, aren't always even....I haven't checked the NC's specs so talking in general. It is common for say 1st to second to be further than 2nd to 3rd and so on. The jump from underdrive to overdrive (5-6 in our case) is often a much larger jump than any other gear. changing the rear sprocket or differential in a car, drops all gears down an equal amount which as Beemerphile states gives a different character to the vehicle since all gears are affected equally.

I dropped the front sprocket 1 tooth which is approximately the same as increasing the rear 3 teeth. It gives the bike a noticeably livelier character. Also gives you a small hit to mpg. I swap the front sprocket depending on what I'm doing. If I was going to stay with the 1 less tooth front all the time I'd would instead go with a 3 tooth larger rear since it is better for the chain to have a larger front sprocket (doesn't have to bend as much).

BTW the sprocket change will throw off the speedometer and odometers. They make speedo healers that will correct it. I know they work on the manual and guess they would also work on the DCT.

 

[670cc]

^^^^+2. I believe there is a service bulletin when the DCT released NOT to change the DCT sprocket ratio.???????

That brings to mind the guy from Europe that had all kinds of goofy shifting problems on his DCT. After the dealer and the Honda reps scratched their heads for a long time, didn't they discover that it had the wrong rear sprocket?

See post 73 in this thread: http://nc700-forum.com/forum/nc750-general-discussion/8985-nc750x-dct-shift-points-normal-2.html

 

[ld_rider]

It almost sounds like all the great things a sprocket change accomplishes (more/different character) can also be done by leaving a DCT in Sport mode ;-)

 

[Old Can Ride]

If it ain't broke I don't fix it. Heck, even sometimes when it is broke I don't fix it. However, this week I did change my chain and sprockets.

 

[Beemerphile]

Lowering the gearing = downshifting...isn't it the same exact thing?

No it isn't. Bamamate hit on it exactly. An example from BMW air-cooled twins: The 1000cc models had final drive ratios of 2:92 for touring and 3:00 or 3:09 for sport models. The 750cc models had 3:20 final drives and the 600cc models had 3:36 final drives. The smaller and weaker the engines (or the "sportier" the model) the lower the rear end ratio they provided. I put a 600cc (3:36) final drive in my 750cc bike to give it better acceleration. It works. BMW didn't just tell the guys with the smaller bikes to downshift. Much easier to change a sprocket than a gear set though. The NC engine is small enough and weak enough that it will feel much more spirited with lower gearing. I know this from having done it with motorcycles and drag racing cars for over 40 years. Add to that, I personally do not like the way the motor feels under about 3500 RPM. You are free to love it that way. I think Honda was going for max fuel economy and optimized in a direction that does not personally suit me. Being a tinkerer, I will simply change it.

The speedo will be in error though. I have a speedo healer to fix that.

Edited to add: I have no experience with the DCT and do not know what it will or will not upset regarding it's superior brain. To LD-Rider, leaving the DCT in "Sport" has the same effect as holding the gears longer with the manual. It does not do the same thing as lowering the gearing.

 

[Beemerphile]

Except that it is correct for ld_rider's scenario, as he does not seem to care to have his NC running 4000 rpm at 55mph in 6th gear.

Neither do I.

So depends on what you're tuning for, doesn't it?

Yep.

 

[rickdc]

Some useful ideas here, thanks. Let me elaborate some on my complaints. When riding in drive mode, the bike hustles into top gear, and wants to stay there. Going up a grade seems to really labor the engine, and although I can downshift manually, it pops right back into 6th unless I speed up. Also, in most situations, it's just fine at highway speed (75-85), however, any kind of headwind, and it wants to slow down, or constantly shift between 5th and 6th. Here, consider this; We have many roundabouts here. I usually downshift to 3rd going in, and would like it to stay there through the whole thing, giving me a little better control and some useful power comming out of it. Well, the bike jumps up one or two gears the second I let off the throttle, and won't downshift fast enough to power out of the last curve. Now, that can be solved by using sport mode, but the high speed thing remains. BTW, I had already bought a new chain and sprocket set, forgot or neglected to specify for DCT, and got the 114 chain and 43t sprocket. I used the chain, keeping the original sprocket. Now I want to try this swap, so I bought another chain.

 

[rippin209]

My NC700X is a manual and I switched to a smaller rear from 43 down to 41. My goal was to lower rpms when going 70-75 mph on the freeway, I commute 60 miles each way on the freeway. It made a small difference but did what I thought it would. Also I thought you couldn't change the sprocket on the DCT?

 

[ld_rider]

Some useful ideas here, thanks. Let me elaborate some on my complaints.

I think your (and many others) complaints are largely self-created figments of your imagination. They are created as result of your previous motorcycle experiences and relationships...

The doctor will elaborate ;-)

The only thing this motorcycle has in common with any other motorcycle that any of us have previously ridden is that it has two wheels. That's it. EVERYTHING else is, believe it or not, a New Concept. Honda calls this New Concept motorcycle the NC700x. I think Honda's concept is not what many riders were expecting when they signed up..

It is a concept that embraces, without clinging to conventional thinking or categories, the appeal engendered by the challenge of diverse possibilities.

Conventional thinking says the engine is lugging. The software engineers, the transmission engineers and the well, engine engineers say it isn't. It is doing exactly what it is designed to do. In fact, I think the NC was designed expressly around the DCT rather than the DCT being designed around the engine (!). Conventional thinking (and resultant complaints) say that the NC shifts too much simply crossing an intersection. My ____only shifted once to get across!...So what? Who cares? What difference does it make? Why is the number of shifts across the intersection important? Why? Because my old bikes only need one, and this New Concept needs three! That is the lament of a rider that "doesn't get" the New Concept.

Conventional thinking (which the New Concept 700x does not adhere to, per Honda's own words) says that motorcycles should have character or feeling. Instead, Honda says:

How might the multi-faceted appeal of a bike change when augmented by comfort, safety and environmental performance?

Wait. What?? Comfort, safety and gasp! Environmental Performance?? I can't imagine that being the lead intro of say a new Harley Davidson Bagger Deluxe Fat Boy Ultra or a BMW S1000RR ;-) Those are the bike oozing with "character" and "feel" ;-)

Toss in Honda's design goal of creating:

An easy-to handle engine with powerful low-to-mid speed torque characteristics and exceptional fuel efficiency


And the whole idea of this motorcycle even remotely stirring the soul or "speaking to me" (whatever that means) goes up in smoke. Running fully loaded into a headwind on a 6% grade @80 mph isn't in the cards. Not congruent with the whole "exceptional fuel efficiency " or "low -mid speed torque speed" New Concept thinking. I will admit that the 270 degree firing was probably done as a nod to "convention" or "character" but that is about it on this motorcycle. I can't imagine the fights they had over that one!

Anyway the doctor suggests you accept the New Concept for what it is.....forgettabout tooling along at 80mph in a head wind, embrace the environment and let the software do its thing with the shifting ;-)

Of course after writing this book about embracing the NC for what it is....I've *cough* invested (wasted? ) about $4,000 in my NC trying to turn it into a mini-Goldwing so what the heck do I know ;-)

 

[Beemerphile]

Thanks Doctor. I feel better already.

Some of us eat what we are served, and some of us treat it as a starting point and try to make it what we want it to be regardless of what the engineers, marketers, accountants, and corporate tree-huggers intended. My bikes have without exception always served my needs (and fit me) better after I was finished with them than they did when I bought them. They may not fit or serve anyone else. They probably would't have broad market appeal. They certainly wouldn't maintain the intended "price point".

And such is the wonder of life, Doc.

 

[DC-Honda]

According to the German forum you can change th he sprocket in the dct without a problem, but installing a speedo healer has to happen directly before the speedometer.
If done like in the non dct, where you can easily plug it in, the dct will get wrong speeds and won't work at all.