Sprocket for higher top speed? - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 22 Old 04-26-2016, 04:44 PM Thread Starter
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Sprocket for higher top speed?

Hey guys, just was wondering if anybody has found a good sprocket setup for getting a little more top speed? Before i say anything else i want to say that im not looking to go over 100 AT ALL, but with the riding that ive been doing and will continue to do, i dont exactly like the feeling of ringing the cbr's neck to stay with the crowd, we constantly ride at around 75 ( yes i know thats speeding, and its also illegal, spare those comments please, i know the potential consequences) but this thing is revving constantly at like 8,500 rpms at that speed and so has anybody came up with a good sprocket set up for that? The 250 off the line keeps up with every one of the bikers i ride with, because they have cruisers and so we do just that, cruise. I realize im going to have to sacrifice some low end torque but im not looking to win any races to begin with. Thanks in advance!


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post #2 of 22 Old 04-26-2016, 05:16 PM
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Did you see this sticky: Performance Forum: Gearing Thread Index ... this index has a number of threads listed which pertain to final drive gearing.
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post #3 of 22 Old 04-26-2016, 08:54 PM
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Two cheapest options:

1. 7% higher gearing. Fit a 15T front. Not sure about the States but i can get one here for less than $20.

2. 6% higher. Slap a CBR300 sprocket on the rear. It has two less teeth than the 250R (36 vs 38)

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post #4 of 22 Old 04-27-2016, 05:03 AM
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Have you owned the bike from new? Check that it's already on standard gearing. At 75mph it should be turning about 7300rpm not 8500.
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post #5 of 22 Old 04-27-2016, 07:38 AM
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Quote:
Originally Posted by Keith View Post
Have you owned the bike from new? Check that it's already on standard gearing. At 75mph it should be turning about 7300rpm not 8500.
Or he could use the 6 gear


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Originally Posted by kiwi rider View Post
Two cheapest options:

1. 7% higher gearing. Fit a 15T front. Not sure about the States but i can get one here for less than $20.

2. 6% higher. Slap a CBR300 sprocket on the rear. It has two less teeth than the 250R (36 vs 38)
I go (ride) with the 300R chainset.
I changed in january.
It's probably the easiest solution.
And (here) the 300R chainset cost, on the bike @ a Honda dealer, less than 100 US alltogether!

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post #6 of 22 Old 04-27-2016, 09:38 AM
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would this also help in fuel mileage too? ...I know, I know kind of the opposite of 'trying to go faster', but if I were to be at a constant 60 or 65 mph, the RPM's would be lower too and one would assume, less revolutions per minute, less fuel?

...........or am I totally off base??? (I'm new to bikes, but in cars this makes sense too)

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post #7 of 22 Old 04-27-2016, 10:01 AM
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For me, it's about the same.
Still 3.3 l/ 100km
Only it does look like 3.5l
Because the Odo is now 6% behind
(of what he showed before)

The CBR250R Gas Mileage Thread

but I have to say, I pretty much drive "ear controlled".
And looking on the Speedo, every now and then, tells me,
I still ride 100 @ 6krpm, where I did that before, too.
Which means, I drive now about 6 % quicker in daily average

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post #8 of 22 Old 04-27-2016, 10:59 AM
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Great site to help you understand the different sprocket sizes and what they do - Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator
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post #9 of 22 Old 04-27-2016, 12:16 PM
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Quote:
Originally Posted by Keith View Post
Have you owned the bike from new? Check that it's already on standard gearing. At 75mph it should be turning about 7300rpm not 8500.
Depends on the region I think. Speedo's are a bit optimistic in places. Here in the states, it is apparently spot-on by my measurements, but my tach reads ~6900RPM at 65MPH.

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post #10 of 22 Old 04-27-2016, 12:19 PM
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cford, many have changed to a 15t front, but this does affect city riding. Usually, many report that the CeeBee doesn't have the balls to really pull any harder with a gear change at the top end, and many say their top speed is actually reduced by changing the gearing. Thinking in an extreme case but applicable, severely reducing the final drive would allow you to theoretically do 60MPH at 4kRPM, but the bike doesn't put out enough HP at those revs to hold that speed. So reducing higher speed RPM doesn't mean you can go faster necessarily.

It may sound/feel like you're ringing its little neck, but trust me, it's built for it and loves it. I contemplated changing gearing, but stayed with the factory gears for several reasons, and not wanting to fool with a speedo healer. Honda knew what they were doing when the paired the gearing combo with the engine characteristics for daily riders.
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