Honda Cbr250R Sprocket Change?

[TylerBKK]

Just curious if anyone has changed the rear sprocket on their CBR250R to a smaller one and if so what differences did you notice? Faster 0-100km? Significant? Faster top end? Waste of time? Cheers...

[mania]

Basically

If you change the "rear" sprocket to a smaller one you will not have faster 0-100 speed

You will have a higher top end speed because you have raised the gearing

If you change the front sprocket to a smaller one you will have the opposite

faster 0-100 & less top end because you have lowered the gearing

Basically you are changing the final gear ratio is all.

There are calculators you can use online to see what the various

configurations will result in.

http://www.gearingcommander.com/

You can select your Honda from the list & play with the configurations & see.

After selecting your bike leave the stock section alone & make your changes in the custom/green section

After that just click on each below to note the differences.

Edited September 10, 2012 by mania

[mcgriffith]

Hey mania- that's a great site.

Thanks for sharing!

[TylerBKK]

Many thanks Mania. That's good stuff. I will check it put. Just in theory though if I changed both front and rear sprockets to a smaller one what would the result be?

[mania]

Many thanks Mania. That's good stuff. I will check it put. Just in theory though if I changed both front and rear sprockets to a smaller one what would the result be?

Yes all there to see what your hypothetical outcome would be.

You could actually cancel out the change in a scenario as you used

To tell you the truth for many seeking something changing both front & back may be needed.

It all depends on what you seek for your application or type of riding

Many folks will just change the front for a number of reasons

1- it is easy to change

2- it gives a bigger result because changing one tooth up or down would require 3-5 teeth in the rear

which of course would mean lengthening or reducing chain length.

But of course what you want from the final ratio may sometimes be a combination of changes to get

it as close as you want.

If your just looking for a general change like more get up & go acceleration through the gears

then maybe just drop a tooth up front & sacrifice some top end. Or add a tooth & go the other way.

All just depends on what your after. A racer of course will gear for the exact track he is riding.

Based on how long the longest straight is etc.

Edited September 10, 2012 by mania

[TongueThaied]

Be careful about going up a tooth on the front sprocket. I did this with my ER6, hoping to compensate for the 5% built in speedometer speed overstatement error. Two things happened. First, going up a tooth on the front sprocket (from 15T to 16T) over compensated the error, resulting in a 5% understatement in actual speed. so I gained nothing there. Going down a tooth on the rear would have been smarter.

The secong thing is harder to figure. I only got 22,000 km on my original chain, despite regular cleaning and lubrication. However, many ER owners in Thailand experienced the same thing. So I replaced it with a Japanese made DID Gold Premium X-Ring chain. I also added a Scottoiler for full time lubrication. During the process I replaced both front and rear sprockets -- 16T on the front. I was expecting to get at least 30,000 km out of this chain.

The Scottoiler kept the chain well-lubed and I gave it regular cleanings. It only needed adjustment once. Imagine my chagrin when the chain was completely trashed by 39K km! I only got 17K km out of the new chain. It did not stretch; but it was stiff and inflexible, popping and making a lot of noise. I feared it would break. The rear sprocket looked pristine. I was tempted to just change the chain and leave both sprokets. But I went ahead and pulled off the drive sprocket cover for an inspection. What I found was that the front drive sprocket was f'ing trashed. The teeth were eaten down to razor sharp little nubs. I couldn't believe it.

I do not know why this happened. I cannot quite grasp the physics behind it, but it was obviously connected to upsizing the front sprocket. So beware of going in this direction. It was an expensive mistake.

[BigBikeBKK]

Be careful about going up a tooth on the front sprocket. I did this with my ER6, hoping to compensate for the 5% built in speedometer speed overstatement error. Two things happened. First, going up a tooth on the front sprocket (from 15T to 16T) over compensated the error, resulting in a 5% understatement in actual speed. so I gained nothing there. Going down a tooth on the rear would have been smarter.

The secong thing is harder to figure. I only got 22,000 km on my original chain, despite regular cleaning and lubrication. However, many ER owners in Thailand experienced the same thing. So I replaced it with a Japanese made DID Gold Premium X-Ring chain. I also added a Scottoiler for full time lubrication. During the process I replaced both front and rear sprockets -- 16T on the front. I was expecting to get at least 30,000 km out of this chain.

The Scottoiler kept the chain well-lubed and I gave it regular cleanings. It only needed adjustment once. Imagine my chagrin when the chain was completely trashed by 39K km! I only got 17K km out of the new chain. It did not stretch; but it was stiff and inflexible, popping and making a lot of noise. I feared it would break. The rear sprocket looked pristine. I was tempted to just change the chain and leave both sprokets. But I went ahead and pulled off the drive sprocket cover for an inspection. What I found was that the front drive sprocket was f'ing trashed. The teeth were eaten down to razor sharp little nubs. I couldn't believe it.

I do not know why this happened. I cannot quite grasp the physics behind it, but it was obviously connected to upsizing the front sprocket. So beware of going in this direction. It was an expensive mistake.

What kind of sprocket was it and where did you get it? Plenty of low quality and knock-off sprockets floating around in Thailand, many labeled and packaged to make them look like something they are not. Same goes for chains too. I only purchase chains and sprockets from reputable dealers (Red Baron and Dirt Shop) or order from abroad. Scottoilers remain unproven but regardless of your maintenance regimen the

Thai climate eats chains faster than back home.

[mania]

+1 Agree with BigBikeBKK

Quality first in chains & sprockets

But I do find it odd that the original wore so quick & also I know DID (your 2nd chain ) is a good brand

So the fact you mentioned the sprocket was trashed could have been the culprit but also

how is your chain alignment?

You probably have already checked but it does not take too much side pressure

of an out of alignment chain to wear a front sprocket pretty quick.

In my experience I do not agree going up or down a tooth on the front increases wear on chain or sprocket.

Just a thought.

Also as BKK mentioned about oilers, Not necessarily a proven product &

with a non enclosed chain a constant oiling will also make the chain a dirt magnet.

Edited September 11, 2012 by mania