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Discussion Starter #1
Given that there are discussions here about improving performance and on gearing, I thought I would put this here.



My riding is primarily around town but even when on the open road, I usually like to stay around 60mph or so. My 500 will pull to 35mph in first, doesn't like to idle along in traffic in first gear without chugging, and doesn't like to be short shifted. Taken together, it just acted like it was geared too high for the way that I like to ride. The only smaller front sprocket that I could find was a 14t which would be about 7% lower. I would have liked to go to a 13t, but I haven't been able to find one.


Anyway, the smaller front sprocket made a noticeable difference. The bike feels peppier. In fact, when pushed hard, it will pull the front tire off the ground when going into second. The gear spacing just feels better. It hits the next gear at a slightly higher RPM which makes a nice difference. When inching along in traffic in town, it still wants to idle along in first faster than I like, but it doesn't chug like it did before. Again, for the way I ride my bike, it was a good improvement overall.



Like I said, I would still like to try a 13t on the front. It is possible that that will be too low as it would put the bike at about 13% lower overall gearing from stock, but it is a simple swap, so it is something I would like to try. Anybody know where I can find a13t front sprocket for my 500?


And for those of you that asked about figuring out the difference when changing sprockets, here is the way that I do it:
First divide the number of teeth on your rear sprocket by the number of teeth on the front. For my 500, that would be 40 divided by 15 which is a final drive ratio of 2.66.
Then do the same with the change you want to make. For me that would be 40 divided by the new 14 front which would then give me the new final drive ratio of 2.85.
Now you just take the first final drive ratio and divide it by the new final drive ratio.

2.66 divided by 2.85 gives a ratio change of .93
The smaller number shows a final drive ratio lowered by about 7%.




If I find a 13t front sprocket, the math looks like this: 40t rear divided by 13t front equals 3.07.
The original ratio was 2.66, so

2.66 divided by 3.07 gives a ratio change of .87
This change will lower my final drive ratio by about 13%



And for those of you that want to gear up: A new 16t front will be 40 divided by 16 which gives a new final drive ratio of 2.5.
So, 2.66 divided by 2.5 gives us 1.06 which means that the new ratio would be 6% higher than the original.
 

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Hey Dave,
Your math is not off, but it's easier to use Gearing commander to calculate gear ratios.

As for the 13 front sprocket - it would have too small radius for the 520 pitch chain. Would still turn, but way too much losses chain bending. You can go a larger sprocket at the rear tho. 14/43 would be essentially the same gearing as 13/40.
 

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Discussion Starter #5
If there is not a 13t available, then it won't matter. But if I could find one, I would still try it. I certainly have ran worse combos.



So who makes a 43 for it?
 

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Hey Dave,
Your math is not off, but it's easier to use Gearing commander to calculate gear ratios.

As for the 13 front sprocket - it would have too small radius for the 520 pitch chain. Would still turn, but way too much losses chain bending. You can go a larger sprocket at the rear tho. 14/43 would be essentially the same gearing as 13/40.

I don't know where you got your information, but after thinking about 13t being too small for the 520 chain, I did a little research. I used to have a Honda 250R three wheeler and I just looked up the chain and sprockets for it. From the factory, it came with a 13t front sprocket and a 520 chain. And the 200 three wheelers came with an 11t and 520 chain. And we used to stock and sell a 10t for them as well.

We raced my old 250R and with mods it would run 75mph. In the 80s we ran many, many 10t and 11t front sprockets on 520 chains in some very severe conditions and often with limited maintenance that probably bordered on neglect. If I can find a 13t for my bike, I will try it and report back the results.


And I have a calculator next to my computer. I know it's old fashioned, but I am old and can calculate the ratio changes with it quicker than I can go to another web site and put in the info there.
 

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Discussion Starter #7
I double checked top speed in the first two gears today. Conservatively, 32+ in first and 55+ in second. It was pulling hard to those speeds in each gear. Correct me if I am wrong, but isn't red line on these 8,500rpm? My 500 doesn't start pulling hard till nearly 20 in first.
 

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I double checked top speed in the first two gears today. Conservatively, 32+ in first and 55+ in second. It was pulling hard to those speeds in each gear. Correct me if I am wrong, but isn't red line on these 8,500rpm? My 500 doesn't start pulling hard till nearly 20 in first.
Isn't the redline value kind of pointless since you have no idea if you're at it or not without a tachometer. If you fee the need to hit the redline between shifts on a cruiser I think you may have the wrong bike!

Just in case your interested and want a laugh, the recommended shifting speeds are below!
 

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I don't know where you got your information, but after thinking about 13t being too small for the 520 chain, I did a little research. I used to have a Honda 250R three wheeler and I just looked up the chain and sprockets for it. From the factory, it came with a 13t front sprocket and a 520 chain. And the 200 three wheelers came with an 11t and 520 chain. And we used to stock and sell a 10t for them as well.

We raced my old 250R and with mods it would run 75mph. In the 80s we ran many, many 10t and 11t front sprockets on 520 chains in some very severe conditions and often with limited maintenance that probably bordered on neglect. If I can find a 13t for my bike, I will try it and report back the results.


And I have a calculator next to my computer. I know it's old fashioned, but I am old and can calculate the ratio changes with it quicker than I can go to another web site and put in the info there.
Just to make clear - I never said a 13 sprocket would not work. What I'm saying it will have excess wear and tear on the chain. Running racebikes with all kinds of odd sprocket combos is completely different than running long miles on the street. A 13/40 sprocket combo has excessively more front tooth contact and due the smaller radius a lot more driveline loss than a 14/43. I've never raced dirt, but done circuit racing and it's clearly measureable on the dyno.

Also what is the service interval of a 250R? A few tens of operating hours? Maintenance is not an issue on a racebike, where despite the dusty environment mileage is minimal, and bikes are maintained often - ateast due the different gearing needs for different tracks. I'm doing long distances on my 500x, and with proper maintenance can get about 30k out of a chain set running 15/41 and 35k on 17/43. Might not be relevant for you or the rebel with it's somewhat less travel oriented seating - but this is important for me.

A quick internet search gave me that JTR makes 43 rear sprockets cor my application (dunno if the rebel has the same hub dimensions) part number is jtr 245/3.43. I bet your calculator doesn't do that. (Pun inteneded) BTW, if you'd check gearingcommander once, you'd find it is a very useful tool which can calculate a lot more things at once than what you could do only in a much longer time with your calculator.

As a sidenote. Not to measure our private parts, but to establish the baseline. Surprisingly I can use a calculator too. In fact, between my MSC in engineering, MBA, and currently pursued PHD in applied mathematics, I can probably calculate even moderately difficult things faster without a calculator than most people can do with it. But I still use tools which are very useful to automate repetitive tasks and can calculate many aspects of things at once. You don't have to enter any information to gearingcommander, just selsct the rebel500 once, and it will start next time with it's parameters. And it calculates all the differences in three defined gearings, top speed or given speed in all gears, sprockets distances, same tooth same link occurences, and many other things at once. I have no affiliation with the developer, but I find it very useful.
 

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Isn't the redline value kind of pointless since you have no idea if you're at it or not without a tachometer. If you fee the need to hit the redline between shifts on a cruiser I think you may have the wrong bike!

Just in case your interested and want a laugh, the recommended shifting speeds are below!
Those shifting speeds are unbelievable. :laugh: Yesterday I had to pass a van on one of the county roads, and I got up to 72mph to get around only to realize I was still in 4th gear. The thing wasn't even remotely coming close to screaming. The power band is vast. :grin2:
 

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Discussion Starter #11
Oyabun sure gets excited when challenged.


"As for the 13 front sprocket - it would have too small radius for the 520 pitch chain. Would still turn, but way too much losses chain bending.



If that isn't saying that it won't work, it is too close for comfort.



Honda has used 13t and smaller front sprockets with the 520 chain for decades and on their front line racing machine to boot. If that combo is good enough for Honda to put on their factory race bike, it will probably be okay for me. If the 13t on 520 application was that bad, why would Honda and other manufacturers use it repeatedly in production machines. It makes no sense. They could have simply used a larger rear sprocket if the smaller front one was inefficient. A little more research will likely result in more examples that might satisfy your concerns.


It looks like your needs and mine in terms of gearing are different. I have no interest in beating up your choices. But you take exception with mine although you have not tried it on a Rebel used for short hops. We can pontificate all we want on subjects where we have no experience. But results trump theory.....every time.


Now on to shift points. Manufacturer recommended shift points are for everyday driving, not maximum performance. In you car, a drive to the grocery store will probably give shift points in traffic in the 2,000RPM range while the red line can often be in the 6,000RPM range. The red line typically indicates the point at which further RPM is unnecessary because the engine power will be rapidly declining thereafter. In racing, this is often referred to as 'nosing over'. This is the best indicator of where to shift for optimum performance, much like your car in 'passing gear'. I selected the maximum shift points on my Rebel based on how it pulled. As long as there is ample acceleration, up go the RPM and speed. When it runs out of power, it is noticeable and after a little practice, you have a good feel for where the best shift point is.



If I am going to the grocery store, I am probably shifting my Rebel out of first in the low 20mph range. But when I spanked my son on his 650, I was shifting out of first in the low 30s.



All I needed was the percentage of reduction each tooth change would give me. Nothing more, nothing less. So I just used the old calculator that I keep next to my keyboard. I have done it this way for years, I was not attacking either you or your preferred web site, so there really was no reason to defend it or to present a list of your credentials. Find something more important to get your panties in a wad over Oyabun.
 

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I was not attacking either you or your preferred web site, so there really was no reason to defend it or to present a list of your credentials.
I wasn't attacking either, but from the tone of your answers you might have felt different. Peace, and enjoy your ride.
 
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