[NVDucati]

I think the issue of sprocket size is pretty straight forward. It isn't complicated but it is complex.
This graphic (I know, I suck at graphics) points out that the engine RPM is the engine RPM without regard to which gear it is in. When you think about Exception C _ that is where the effect kicks in and the complexity and arguments start. Otherwise, the tooth count (final drive ratio) only slides the RPMs up and down the speed scale.

Zimmer's flat track example is true because whatever RPM our roll-on acceleration was the best ... we would swap sprockets for that track and that night's dirt so as to have the most acceleration as we exited the last turn towards the finish line. Thus for street bikes our personal riding style, our favorite road types, and the few little changes we make to the engine add up to how we perceive the 16 vs 15.

My larger point remains that if we "morph" our riding style to best utilize the aggregate slight changes we make to the air in/air out, air/fuel ratio and final drive ratio ... things are better.

[zimmemr]

I think the issue of sprocket size is pretty straight forward. It isn't complicated but it is complex.
This graphic (I know, I suck at graphics) points out that the engine RPM is the engine RPM without regard to which gear it is in. When you think about Exception C _ that is where the effect kicks in and the complexity and arguments start. Otherwise, the tooth count (final drive ratio) only slides the RPMs up and down the speed scale.

Zimmer's flat track example is true because whatever RPM our roll-on acceleration was the best ... we would swap sprockets for that track and that night's dirt so as to have the most acceleration as we exited the last turn towards the finish line. Thus for street bikes our personal riding style, our favorite road types, and the few little changes we make to the engine add up to how we perceive the 16 vs 15.

My larger point remains that if we "morph" our riding style to best utilize the aggregate slight changes we make to the air in/air out, air/fuel ratio and final drive ratio ... things are better.

+1 I couldn't agree more, especially the last bit. 

[6504me]

I think the issue of sprocket size is pretty straight forward. It isn't complicated but it is complex.
This graphic (I know, I suck at graphics) points out that the engine RPM is the engine RPM without regard to which gear it is in. When you think about Exception C _ that is where the effect kicks in and the complexity and arguments start. Otherwise, the tooth count (final drive ratio) only slides the RPMs up and down the speed scale.

Zimmer's flat track example is true because whatever RPM our roll-on acceleration was the best ... we would swap sprockets for that track and that night's dirt so as to have the most acceleration as we exited the last turn towards the finish line. Thus for street bikes our personal riding style, our favorite road types, and the few little changes we make to the engine add up to how we perceive the 16 vs 15.

My larger point remains that if we "morph" our riding style to best utilize the aggregate slight changes we make to the air in/air out, air/fuel ratio and final drive ratio ... things are better.

Another consideration is that the gear ratios are rumored to have been changed in the 2021 models...

https://www.webbikeworld.com/2021-royal-enfield-int650/ third paragraph.

I have not verified that in the dealer's (most reliable) parts lookup but my 2021's gear spacing seemed different than the 2019 demo I rode.

[Jack Straw]

"Mountain, meet Molehill"    How many pages will this one go for?

One lousy tooth on the countershaft sprocket. What's the fuss?  It either works for you or it doesn't.

The pretty colored charts ARE cute though.

Many of us learned the theory behind final drive ratios with our first 10 speed bicycle.  But really, no theory needed at all, It either works for you, or it doesn't.

Oh, one more thing......... get off my lawn.

[whippers]

I don't have a dog in this fight, but as anyone that's ever ridden a dirt tracker, where a one tooth difference on the rear sprocket, let alone the front, might make the difference between winning and being the first loser your remark that "it's a little more complicated etc.) Is right on the mark. 

I am hoping you realise that Racing is a totally different scenario to the street because you are gearing to a particular circuit and optimising a set of compromises.  I'll reply to the other guy then I'm out of this. If we can't agree that raising the gearing reduces rear wheel thrust and thus acceleration then we don't agree on physics.

[whippers]

Maybe you can wait till you’ve actually fitted the taller front sprocket to have an opinion? It’s a little more complicated than taller/ slower///shorter quicker.

If we can't agree that raising the gearing reduces rear wheel thrust and thus acceleration then we don't agree on physics. Enjoy your ride

[zimmemr]

I am hoping you realise that Racing is a totally different scenario to the street because you are gearing to a particular circuit and optimising a set of compromises.  I'll reply to the other guy then I'm out of this. If we can't agree that raising the gearing reduces rear wheel thrust and thus acceleration then we don't agree on physics.

I don't think anyone is saying that. I was merely trying to point out that there are nuances to changing the gearing. For example if your engine can't pull the taller gearing, your top speed may be reduced and the converse is just as true in some cases lowering the gearing may increase the top speed. I'm sure you knew that, but I 'm just as certain that's not universally known on this forum. And I think we'd both agree that's as true on the street as it is on the race track.

 But I think it's a good idea to end this topic. It takes maybe an hour to change the sprocket the first time you've done it, maybe twenty minutes the the 10th time. My advice is fit the larger sprocket and see how you like it, if you don't like it change it back, or put a 14 tooth on there and become the Interceptor wheelie king. There's no need to hash this thing to death. 

[CPJS]

For gaining more info, I would find it interesting how changing to a 16t front sprocket changes things with reference to any other changes made to the bike and which model INT or GT.
How much difference (if any) does having the full exhaust system/air filter mod make to pulling higher revs in higher gears?
Does the upright riding position of the INT make a difference to having longer gearing?
How is it with a pillion?
Is there someone out there with a stock bike who is going make exhaust/filter changes, are the willing to do a sprocket change first to find out how the other mods affect it?

[zimmemr]

For gaining more info, I would find it interesting how changing to a 16t front sprocket changes things with reference to any other changes made to the bike and which model INT or GT.
How much difference (if any) does having the full exhaust system/air filter mod make to pulling higher revs in higher gears?
Does the upright riding position of the INT make a difference to having longer gearing?
How is it with a pillion?
Is there someone out there with a stock bike who is going make exhaust/filter changes, are the willing to do a sprocket change first to find out how the other mods affect it?

The short version is that the more torque your engine makes the taller you can gear.
The more slippery the bike is, the higher you can gear, but at normal riding speeds this is basically a non issue. The OEM mirrors offer as much wind resistance if not more than almost anything else on a naked bike.

If top speed is your objective gear it so it pull the maximum revs in 6th, in some cases that may require lowering the gearing in others raising it. It all depends on the bikes weight, aerodynamics and power.

As I've said before read Kevin Cameron's Sport bike Performance Handbook, especially the chapter on final drives and all be revealed.

[supercub]

Small bore bikes are a blast when set up to rider preference. I would try a sprocket change before messing with tuning if all I want to do is make the shifting more compatible with my usual ride, yea I'l go for it. Tuning is complicated and a sprocket change is easy.

[zimmemr]

Small bore bikes are a blast when set up to rider preference. I would try a sprocket change before messing with tuning if all I want to do is make the shifting more compatible with my usual ride, yea I'l go for it. Tuning is complicated and a sprocket change is easy.

Give the man a seegar!

[Starpeve]

I am hoping you realise that Racing is a totally different scenario to the street because you are gearing to a particular circuit and optimising a set of compromises.  I'll reply to the other guy then I'm out of this. If we can't agree that raising the gearing reduces rear wheel thrust and thus acceleration then we don't agree on physics.

Simplistic overview. Done.

[lucky phil]

Another consideration is that the gear ratios are rumored to have been changed in the 2021 models...

https://www.webbikeworld.com/2021-royal-enfield-int650/ third paragraph.

I have not verified that in the dealer's (most reliable) parts lookup but my 2021's gear spacing seemed different than the 2019 demo I rode.

Easy enough to confirm if anyone has access to a 2021 parts catalog. Just cross ref the part numbers to the 2020 model.

Ciao

[Hoiho]

Had a good run with it today and I think it’s an improvement.
3700-3750rpm at 100km/h, and 4500 At 120, so it feels more relaxed on the open road for sure.

Did our usual hill loop and found it only slowed me a bit burying the throttle exiting a slow corner compared to mates std geared bike, but I could catch up by holding the gear longer.

I found the sprocket nut was little more than hand tight, held on by the tab washer only...

[CPJS]

The short version is that the more torque your engine makes the taller you can gear.
The more slippery the bike is, the higher you can gear, but at normal riding speeds this is basically a non issue. The OEM mirrors offer as much wind resistance if not more than almost anything else on a naked bike.

If top speed is your objective gear it so it pull the maximum revs in 6th, in some cases that may require lowering the gearing in others raising it. It all depends on the bikes weight, aerodynamics and power.

As I've said before read Kevin Cameron's Sport bike Performance Handbook, especially the chapter on final drives and all be revealed.

Unfortunately your short version does not answer any of my questions.
I understand what gearing does, that is not what I asked.
I have not read Mr. Camerons book but I doubt it mentions the RE650 in particular and how changing the exhaust affects it's ability to pull higher gearing.
I am sure the book will have the means to show you how to calculate the end result if you have all the information,  we don't have it, until we do, the book won't help much.
With so many variables, the more facts we get the more people can get an idea what to expect with different modifications. It doesn't matter whether a modification feels better or worse, that is subjective and only relative to their particular needs/objectives.
For pure street riding I'll start off with a bit of info I have so far found.
With stock gearing in 5th gear my bike could hit the rev limiter showing 105mph. With the 16tooth sprocket it will only pull 7200 revs however the the speed has risen to 110mph. This was done with me crouched down as much as possible.
I am only 5'6" 160lbs riding a GT on OE tyres with the TEC Stinger exhaust system, free flowing air filter and booster plug.