Chain and Sprocket Discoveries...

[ExpatJohnny]

Just wanted to impart some discoveries I've made in modding this little bike for daily driving and occasional knee dragging....

I've tried the following combinations and here's what I've found...
15t F 45t R = Slow Launch, Not really any better top speed, and smooth lowered rpm on the freeway, not much passing power though.

13t F 45t R = 1st and 2nd gear become useless, if not just to get going, and third becomes a really quick roll. Revs a little high on the freeway, and don't even think of trying to go over ninety on a warm day.

and finally... My Favorite!
14t F and 47t R with 520/108 Chain = It Pulls harder than stock in all gears, yet somehow is actually able to attain a higher top speed. I think this is due to the engine being able to deliver it's power band more efficiently.

When I had the stock of 14t F and 45t R, I was able to get it up to approx 110 indicated. It was in the 60's outside.
With the current setup, in the 60's outside again, I was able to get it up to an indicated 115 - 117.

[csmith12]

Welcome Johny!

Thanks for sharing.

[Alex]

I'm not sure why you're seeing such a difference between 13/45 and 14/47. The two ratios for those sprockets are different by 3%, nothing that would show anywhere near a 20 mph difference in comfortable top speed.

13/45: 3.462
14/47: 3.357

[choneofakind]

Originally Posted by Alex

I'm not sure why you're seeing such a difference between 13/45 and 14/47. The two ratios for those sprockets are different by 3%, nothing that would show anywhere near a 20 mph difference in comfortable top speed.

13/45: 3.462
14/47: 3.357

14/45: 3.214

The difference between the 13/45 and the 14/47 is .105
The difference between the 14/45 and the 14/47 is .143
That's a close enough difference between them that 14/47 is just about half way between stock and 13/45.
If 13/45 is too short, and 14/45 is too tall, maybe 14/47 is just right for getting the power band where it's most effective?

You would likely be able to feel the difference between each of the final drives by how it accelerates, but I'll equate the large speedo difference in top speed with the adrenaline from getting to terminal velocity.

[ExpatJohnny]

@ choneofakind Thanks for the assist.

Yeah for whatever reason IMHO the 14/47 feels like the best acceleration improvement over stock without loss of top speed. I felt the 13t front resulting in reving close to 1k rpms higher in 6th gear at freeway speeds. With 14/47 I'm only running about 400-500 rpms higher.

It just seems to me there are a lot of sprocket choices available, to suit individual tastes and needs, but the 14/47 combo feels like it should have come from the factory.... Since it doesn't lose top end and improves acceleration.

[choneofakind]

Eh, the difference is still only 4 mph. I feel like that also might have been caused by a difference in riding position/ambient temp/wind/grade of the road etc.

The feedback on the gearing is good to have though

[flynjay]

I've read that the 13T front will lead to severe reduction in chain life due to the chain having to turn a tighter corner.

Eventually I plan on trying the 15/45 on my pregen. Of course we (pregen owners) have a tiny bit more top end than you new gen folks.

I'd like to keep my freeway rpm's in the 8-9k range for cruizing.

[choneofakind]

Originally Posted by flynjay

I've read that the 13T front will lead to severe reduction in chain life due to the chain having to turn a tighter corner.

That's why I went +2 in the back, instead of -1 in front. Needed new chain and Sprockets anyways, and I don't ride freeway unless I need to, so I figured I might as well get some better pull coming out corners without having to downshift to 2nd. 3rd is the best for me in twisties; pulls well down from 5k, but rips up to redline quick also

[flynjay]

Originally Posted by choneofakind

That's why I went +2 in the back, instead of -1 in front. Needed new chain and Sprockets anyways, and I don't ride freeway unless I need to, so I figured I might as well get some better pull coming out corners without having to downshift to 2nd. 3rd is the best for me in twisties; pulls well down from 5k, but rips up to redline quick also

Well, it's all about finding what works for you so

[Alex]

Originally Posted by ExpatJohnny

Yeah for whatever reason IMHO the 14/47 feels like the best acceleration improvement over stock without loss of top speed. I felt the 13t front resulting in reving close to 1k rpms higher in 6th gear at freeway speeds. With 14/47 I'm only running about 400-500 rpms higher

It might feel like that, but the math doesn't bear that out. The differences just aren't that large, and there's no way there is a difference of 500+ rpm at highway speeds between those two choices of ratios.

Here's a great site to play with all ratios and see what results are (speed/vs gearing) across the board.

www.gearingcommander.com

With 14/47 gearing, at 10,000 RPM in 6th the bike is going 77.72 mph.
With 13/45 gearing, at that same 10,000 RPM in 6th the bike is going 75.38 mph. If you bump it up to that same speed of 77.7 mph, the RPM's would only be 10,240.

[ExpatJohnny]

Thanks for the link Alex... Good site you have BTW.