Are you able to redline in top gear? - Page 2 - Honda CBR250R Forum : Honda CBR 250 Forums
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post #11 of 101 Old 09-20-2011, 08:17 AM
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We'll never redline in top with standard gearing.. it would be over 170kph.

Just go up 2 teeth on the rear sprocket and enjoy better accelaration and a fractionally better top speed anyway.

All bikes are on the tall side to pass ride by noise testing.. especially 23hp thai commuter bikes.



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post #12 of 101 Old 09-20-2011, 09:35 AM
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Originally Posted by Aufitt View Post
Just go up 2 teeth on the rear sprocket and enjoy better accelaration and a fractionally better top speed anyway.
So that will improve both top-end and acceleration?
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post #13 of 101 Old 09-20-2011, 09:41 AM
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Aufitt got it - it's the gearing.

The CBR doesn't have enough power to pull the stock top gear to reline - no matter what you do or weight or...

You need to gear-down, as Aufitt said, to get your top gear RPMs higher and get the engine closer to peak power. If you do, your cruise RPMs will be higher as well, which could be a pain. Most cycles will not pull top gear to redline, usually because typical highway cruise gets too hectic.

As far as reving, there's usually no reason to hit the rev limiter - even if you are trying for max acceleration. I'll look for a dyno chart (EDIT -http://sites.google.com/site/tommysc...e/Untitled.jpg, from that dyno chart I'd shift at 10,000RPMs most of the time - slighly higher from 5th to 6th) , but generally if you just slightly (500 RPM) exceed the RPM where max HP is made before shifting you will stay close to the power peak for the most time - giving you best acceleration. Don't be afraid to spin the CBR's engine - it's designed to live comfortably at higher RPMs. Use a quality oil (synthetic is always my choice) and change it often enough - more often than the manual suggests IMO.

Really, unless you change your gearing significantly or do a lot of mods the CBR isn't going to be much faster. You just have to deal with that or buy something bigger.

Last edited by jkv357; 09-20-2011 at 09:53 AM.
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post #14 of 101 Old 09-20-2011, 09:43 AM
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So that will improve both top-end and acceleration?
Not typically, but in this case - yes.
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post #15 of 101 Old 09-20-2011, 09:43 AM
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Originally Posted by Rick View Post
If you can't get to redline in 6th gear sounds like a warranty repair to me.
I have to guess that you're talking out of your ass.

I don't think I've heard of anyone hitting redline in 6th on this bike. Certainly not in stock form anyway.

Last edited by Redline; 09-20-2011 at 10:52 AM.
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post #16 of 101 Old 09-20-2011, 09:44 AM
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^^ What case? The CBR250R will get both increased acceleration and top-end with +2 on the rear sprocket?
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post #17 of 101 Old 09-20-2011, 10:00 AM
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Originally Posted by Redline View Post
^^ What case? The CBR250R will get both increased acceleration and top-end with +2 on the rear sprocket?
The gap from 5th to 6th is pretty large. For maximum top speed you'd need to find the gearing that put the engine at 10,000RPMs in top gear. You are fighting aerodynamic drag at that point, and there is a speed that your maximum power will not take you past based on the aerodynamics of the particular cycle.

Basically you'd need to test with different gearing to come up with the optimum combination that would put you right at the power peak at the highest speed.
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post #18 of 101 Old 09-20-2011, 10:52 AM
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Okay, not sure that explains how it will improve both of them though.
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post #19 of 101 Old 09-20-2011, 11:05 AM
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Originally Posted by Redline View Post
Okay, not sure that explains how it will improve both of them though.
I guess it didn't, so -

Adding teeth to the rear sprocket or subtracting from the front (lower gearing) will increase acceleration. The engine will pull through each gear quicker and easier. You'll be shifting more often and not going as far in each gear, but your acceleration will be better. Same as a bicycle with multiple gears - it's easier to accelerate with a larger rear gear, but you are peddling faster for the speed you are going.

Because of the tall 6th gear, the same change will get your RPMs closer to the power peak in top gear as you near top speed - as described above.
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post #20 of 101 Old 09-20-2011, 01:11 PM
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You mean that "lighter" rear sprocket will allow 6th gear to rev higher so improve top end speed?
But will make all the other gears shorter.

I don't think is worthy, considering how often I find myself struggling to go faster in 6th gear than how often I use other gears at "standard" speeds...
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