[br]Since I did this conversion, alot of people have been asking me about where to buy the sprockets, how much, is it worth doing.. etc etc. So I thought I'd do a write up which can answer all the questions people might have in reguards to it, and include a walkthrough into how it may be done.
[red]Background info[/size=6][/red]
The cbr250rr's stock sprocket setup consists of a 52 tooth rear sprocket and a 17 tooth front sprocket. From memory the chain is 136 link, however im not sure of the pitch. This is the regular setup any stock cbr250rr will come with.
So, why would we want to change the size of the sprockets? Well.. the less teeth we have on the front sprocket, and the more teeth we have on the rear sprocket will determine how much faster the chain will run along the sprockets and rotate the rear wheel. The higher the rate of which the rear wheel rotates in a set amount of time, the more acceleration we have. There is ofcourse downsides to doing this, but that will be discussed later.
Why 14/53? why not any other combination of sizes? well the stock sprockets of the cbr250rr are only sold with either 52 teeth, or 54 teeth from most bike stores. You can ofcourse use the 54t rear sprocket with the stock 17t front, however that will only grant you 4% increase in acceleration (gay). The 14/53 sources sprockets from other bikes, and a different chain to give you a very nice increase of acceleration without losing too much top end speed (will be discussed later) so we could say it would be the optimum sprocket conversion to go for, with the parts which are available to us, and will fit on the cbr250. In saying this, none of the new sprockets, or chain, are designed for the cbr250. The front sprocket is off the VTR250, and the rear sprocket is off some old dirt bike, however they do fit the cbr250 perfectly, so don't worry too much about this.
[red]Purchasing[/size=6][/red]
I bought my sprockets and chain from MCA in Auburn and the city. Most other bike stores should sell them, however they might have to order the rear sprocket in, which could take time. They are usually more expensive aswell. I would suggest to buy from MCA.
Firstly, give them a call and see if the sprockets and chain are in stock. Dont mention that they are for a cbr250 otherwise it will confuse them, and they will start blabbering on about how the sprockets you are inquiring about won't fit your bike (they don't know about this uber sprocket mod).
Instead tell them to look up in the link international book (this is the book they use to source and track down all the parts in store) for the sprocket codes:
31-kvo 14 tooth - This is the front sprocket. It is from the VTR250
32-428 53 tooth - This is the rear sprocket. It is from a dirt bike, so tell them to look it up in the dirt bike section of the book, otherwise they will tell you they don't have it.
Lastly ask for a 120 link, 520 pitch chain. They have a few of these, they vary in quality and price, so it is up to you with which one you go for. I went for the cheapest which was the RK 520S0 O-Ring chain.
The prices you should be paying for these are:
Front sprocket - $17? (cant remember for sure though)
Rear sprocket - $55
Chain - $136 (for the cheapest)
If they dont have something in stock, ring other MCA stores and see if they have them. I got my front sprocket and chain from Auburn and rear sprocket from the city store. If no one has them, ask them to order one in. They will do it.
Here are some pictures of what everything looks like, dont be alarmed at the size of the rear sprocket. I almost shat my pants when I saw how big it was.
![]()
Rear Sprocket^[/size=3]
![]()
Front Sprocket^[/size=3]
![]()
Chain^[/size=3]
[red]Converting the sprockets[/size=6][/red]
What you will need:
- Rear Stand
- Your trusty tool kit. wont go into too much info
- Breaker bar will be very useful
- Angle Grinder or chain breaker tool.
- your new sprockets and chain.
Start by removing your LHS fairing. Once it is off, move down to your front sprocket cover. Remove the speedo drive, and then the sprocket cover. If you got alot of gunk and shit in here, I suggest you give it a good cleaning. When your front sprocket is exposed, you will need to loosen the bolt holding it on (the big one right in the centre). This has been a very annoying task for most and it will be the part where a breaker bar will save your life. You will also need to make sure your bike is in gear when you try and remove this bolt. I did it in one go with a long breaker bar.Proceed by removing the front sprocket, and just let the chain hang down.
Raise your bike on the rear stand and remove the rear wheel and put it aside. Now if go get your angle grinder/chain breaker tool and cut through your old chain and take it off and throw it in the bin.
Pull the rear sprocket off the back wheel and replace it with your new sprocket, put it back into the cush drive housing, and put your rear wheel back on.
So now you should have both your new front and new rear sprocket on, with no chain.
Now you will need to get your new chain and cut 3 links off it. Do this with an angle grinder or chain breaker tool, and install it.
Put everything back on, and your ready to go!
[red]Pro's and Con's[/size=6][/red]
Here is a review which I wrote about the mod, and what I thought on my very first ride. I mounted a camera for my ride to try to give you a better idea of how the acceleration is, although it turned out very shakey: http://www.youtube.com/watch?v=PxJsLROT_as
Review:
I was at first hesitant to go with this setup, as the size of the rear sprocket kinda threw me off when I bought it. Nevertheless, After some convincing from Fatty, I went ahead and bought the sprockets and chain and took them home to be fitted.
I was aiming to do the whole thing in a few hours, although that few hours stretched to a few days, and then became a full week (stupid work) and the suspense of trying her out was getting to me. But FINALLY.. everything is back on the bike, and she was ready this morning to go on her maiden voyage with the new 14/53 sprocket setup.
She glided out the garage like a pushbike, no resistance whatsoever.. mmm.. the feeling of new sprockets. I fired her up, and she awakened with a deafening roar, much to the dislike of sleeping neighbors.
I didn't thrash her all that much to start, I went around for 5 minutes getting everything warmed up, but even so, I could feel her pulling away like a whole different bike. I came around the block, stopped outside my house and waited for a clear road to let her rip.
I jumped on the throttle, opened it all the way up, and within 2 seconds (quite literally) I was at redline in first gear, and going WTF!! where did my revs go!?! The front wheel nearly lifted off while I was in sitting position, I guess the 115 sized jets and unifilter played a part in that aswell.
Pushed her into second, and the same thing. 2 seconds and I was at redline again. At this point, I hadn't noticed a loss in speed, it felt like I was still traveling at however many km/h it was, but the acceleration took me there much, much quicker. To be honest, I felt like I had a brand new bike.
It was once I got up into 5th gear that I noticed.. shit, my left foot is going nuts with shifting. This was the first downside I noticed. You are shifting like crazy, to a point where it felt weird. From memory I had to take it into 4th or 5th gear just to ride down my street without sounding like a F1 car on steroids.
At this point I was still pretty excited at the new acceleration, but was bummed out at the rate of gear switches I had to do, I wasn't expecting it to eat through gears that fast.
By the time I got home after a short half hour ride, I was happy with the sprocket conversion, but if I had the choice again I think I would go with the 17/54 to be honest. The reason why this conversion works pretty nicely on the mc22 is that it revs to 20k (from memory). So it is quite nice that you can take it to redline and still be putting out a decent speed, unlike other learner bikes I have ridden.
I would like to try get a camera mounted to the bike and take a video to show you just what its like. I'll try to do this by the end of the day.
All in all, I don't think I could ever go back to the stock 17/52 after I have tried out the 14/53, but if I still have my bike by the next time I need a change of sprockets and chain, I think I will go with 17/54. Although I am still VERY pleased with it, and the acceleration which it puts out is nuts! (definitely doesn't feel like you're on a 250 anymore)
Here are the actual pro's and cons:
Pro's[/size=3][/size=3]
- crazy acceleration
- its cheap to do the conversion
- It will beat any other cbr250rr you race
- its fucking crazy, just take my word for it, and do it
Con's[/size=3][/size=3]
- Reduced top speed. Some say that your top speed is reduced to 160hm/h, however I have broken that and taken my bike to somewhere close to 180km/h I believe. But when are you gonna go that fast on a aussie road (legally) anyway.
- your speedo will show that you are going faster then you actually are
- Your engine and gearbox will have approximately 18% less life.
- You will be shifting gears much more, however you will get used to this
![]()
I ride a CBR250RRR...The extra R is for Red.
[red]Background info[/size=6][/red]
The cbr250rr's stock sprocket setup consists of a 52 tooth rear sprocket and a 17 tooth front sprocket. From memory the chain is 136 link, however im not sure of the pitch. This is the regular setup any stock cbr250rr will come with.
So, why would we want to change the size of the sprockets? Well.. the less teeth we have on the front sprocket, and the more teeth we have on the rear sprocket will determine how much faster the chain will run along the sprockets and rotate the rear wheel. The higher the rate of which the rear wheel rotates in a set amount of time, the more acceleration we have. There is ofcourse downsides to doing this, but that will be discussed later.
Why 14/53? why not any other combination of sizes? well the stock sprockets of the cbr250rr are only sold with either 52 teeth, or 54 teeth from most bike stores. You can ofcourse use the 54t rear sprocket with the stock 17t front, however that will only grant you 4% increase in acceleration (gay). The 14/53 sources sprockets from other bikes, and a different chain to give you a very nice increase of acceleration without losing too much top end speed (will be discussed later) so we could say it would be the optimum sprocket conversion to go for, with the parts which are available to us, and will fit on the cbr250. In saying this, none of the new sprockets, or chain, are designed for the cbr250. The front sprocket is off the VTR250, and the rear sprocket is off some old dirt bike, however they do fit the cbr250 perfectly, so don't worry too much about this.
[red]Purchasing[/size=6][/red]
I bought my sprockets and chain from MCA in Auburn and the city. Most other bike stores should sell them, however they might have to order the rear sprocket in, which could take time. They are usually more expensive aswell. I would suggest to buy from MCA.
Firstly, give them a call and see if the sprockets and chain are in stock. Dont mention that they are for a cbr250 otherwise it will confuse them, and they will start blabbering on about how the sprockets you are inquiring about won't fit your bike (they don't know about this uber sprocket mod).
Instead tell them to look up in the link international book (this is the book they use to source and track down all the parts in store) for the sprocket codes:
31-kvo 14 tooth - This is the front sprocket. It is from the VTR250
32-428 53 tooth - This is the rear sprocket. It is from a dirt bike, so tell them to look it up in the dirt bike section of the book, otherwise they will tell you they don't have it.
Lastly ask for a 120 link, 520 pitch chain. They have a few of these, they vary in quality and price, so it is up to you with which one you go for. I went for the cheapest which was the RK 520S0 O-Ring chain.
The prices you should be paying for these are:
Front sprocket - $17? (cant remember for sure though)
Rear sprocket - $55
Chain - $136 (for the cheapest)
If they dont have something in stock, ring other MCA stores and see if they have them. I got my front sprocket and chain from Auburn and rear sprocket from the city store. If no one has them, ask them to order one in. They will do it.
Here are some pictures of what everything looks like, dont be alarmed at the size of the rear sprocket. I almost shat my pants when I saw how big it was.
Rear Sprocket^[/size=3]
Front Sprocket^[/size=3]
Chain^[/size=3]
[red]Converting the sprockets[/size=6][/red]
What you will need:
- Rear Stand
- Your trusty tool kit. wont go into too much info
- Breaker bar will be very useful
- Angle Grinder or chain breaker tool.
- your new sprockets and chain.
Start by removing your LHS fairing. Once it is off, move down to your front sprocket cover. Remove the speedo drive, and then the sprocket cover. If you got alot of gunk and shit in here, I suggest you give it a good cleaning. When your front sprocket is exposed, you will need to loosen the bolt holding it on (the big one right in the centre). This has been a very annoying task for most and it will be the part where a breaker bar will save your life. You will also need to make sure your bike is in gear when you try and remove this bolt. I did it in one go with a long breaker bar.Proceed by removing the front sprocket, and just let the chain hang down.
Raise your bike on the rear stand and remove the rear wheel and put it aside. Now if go get your angle grinder/chain breaker tool and cut through your old chain and take it off and throw it in the bin.
Pull the rear sprocket off the back wheel and replace it with your new sprocket, put it back into the cush drive housing, and put your rear wheel back on.
So now you should have both your new front and new rear sprocket on, with no chain.
Now you will need to get your new chain and cut 3 links off it. Do this with an angle grinder or chain breaker tool, and install it.
Put everything back on, and your ready to go!
[red]Pro's and Con's[/size=6][/red]
Here is a review which I wrote about the mod, and what I thought on my very first ride. I mounted a camera for my ride to try to give you a better idea of how the acceleration is, although it turned out very shakey: http://www.youtube.com/watch?v=PxJsLROT_as
Review:
I was at first hesitant to go with this setup, as the size of the rear sprocket kinda threw me off when I bought it. Nevertheless, After some convincing from Fatty, I went ahead and bought the sprockets and chain and took them home to be fitted.
I was aiming to do the whole thing in a few hours, although that few hours stretched to a few days, and then became a full week (stupid work) and the suspense of trying her out was getting to me. But FINALLY.. everything is back on the bike, and she was ready this morning to go on her maiden voyage with the new 14/53 sprocket setup.
She glided out the garage like a pushbike, no resistance whatsoever.. mmm.. the feeling of new sprockets. I fired her up, and she awakened with a deafening roar, much to the dislike of sleeping neighbors.
I didn't thrash her all that much to start, I went around for 5 minutes getting everything warmed up, but even so, I could feel her pulling away like a whole different bike. I came around the block, stopped outside my house and waited for a clear road to let her rip.
I jumped on the throttle, opened it all the way up, and within 2 seconds (quite literally) I was at redline in first gear, and going WTF!! where did my revs go!?! The front wheel nearly lifted off while I was in sitting position, I guess the 115 sized jets and unifilter played a part in that aswell.
Pushed her into second, and the same thing. 2 seconds and I was at redline again. At this point, I hadn't noticed a loss in speed, it felt like I was still traveling at however many km/h it was, but the acceleration took me there much, much quicker. To be honest, I felt like I had a brand new bike.
It was once I got up into 5th gear that I noticed.. shit, my left foot is going nuts with shifting. This was the first downside I noticed. You are shifting like crazy, to a point where it felt weird. From memory I had to take it into 4th or 5th gear just to ride down my street without sounding like a F1 car on steroids.
At this point I was still pretty excited at the new acceleration, but was bummed out at the rate of gear switches I had to do, I wasn't expecting it to eat through gears that fast.
By the time I got home after a short half hour ride, I was happy with the sprocket conversion, but if I had the choice again I think I would go with the 17/54 to be honest. The reason why this conversion works pretty nicely on the mc22 is that it revs to 20k (from memory). So it is quite nice that you can take it to redline and still be putting out a decent speed, unlike other learner bikes I have ridden.
I would like to try get a camera mounted to the bike and take a video to show you just what its like. I'll try to do this by the end of the day.
All in all, I don't think I could ever go back to the stock 17/52 after I have tried out the 14/53, but if I still have my bike by the next time I need a change of sprockets and chain, I think I will go with 17/54. Although I am still VERY pleased with it, and the acceleration which it puts out is nuts! (definitely doesn't feel like you're on a 250 anymore)
Here are the actual pro's and cons:
Pro's[/size=3][/size=3]
- crazy acceleration
- its cheap to do the conversion
- It will beat any other cbr250rr you race
- its fucking crazy, just take my word for it, and do it
Con's[/size=3][/size=3]
- Reduced top speed. Some say that your top speed is reduced to 160hm/h, however I have broken that and taken my bike to somewhere close to 180km/h I believe. But when are you gonna go that fast on a aussie road (legally) anyway.
- your speedo will show that you are going faster then you actually are
- Your engine and gearbox will have approximately 18% less life.
- You will be shifting gears much more, however you will get used to this
I ride a CBR250RRR...The extra R is for Red.
