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Discussion Starter · #1 ·
These bikes are a bit of a toy a little shy on power. Without any foreseeable major additions of horsepower, we are going to work on looks and weight savings.
Eventually we will get into the suspension maybe look into a camshaft or a big bore kit.
 

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Discussion Starter · #2 ·
Here is the bike, all but stock. The only piece so far changed is a 15T sprocket up front to make the lower gears more use able and to drop the RPM on the freeway.

Oh and this is my girlfriend's bike, but I still take it out from time to time.
 

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Discussion Starter · #3 ·
Today the replacement exhaust hanger arrived from Thailand. This bike will never carry a passenger so it's giving up the passenger pegs.

The total weight savings is 2 lbs between the passenger peg brackets and the exhaust hanger.
 

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Discussion Starter · #4 ·
We've got an exhaust on order from Italy which isn't supposed to arrive until after September 21.

We'll also be getting a fender delete, integrated taillight, and the handles out back will be going as well. Not sure if I'll be just getting the deletes for the handles or if I'll try to utilize the space for something else.
 

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Today the replacement exhaust hanger arrived from Thailand. This bike will never carry a passenger so it's giving up the passenger pegs.

The total weight savings is 2 lbs between the passenger peg brackets and the exhaust hanger.
Good stuff, have you seen my thread 'put your 300 on a diet'?

http://www.cbr300forum.com/forum/cbr300-general-discussion-forum/2458-put-your-300-diet.html

Ive reduced the stock weight by 28lbs so far. Noticeable increase in acceleration and improvement in handling esp 'flickability' when canyon racing or at track days.
 

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I must complement you on the way you are going with this. I'm not a big mod for mod's sake sort of guy but I can see a logic to what you are doing here.
Can I ask who has the greatest input to this program and what the motivation behind it is?

Oh BTW carrying a pillion is not a good experience, well for them anyway as my friend found to his chagrin. Ok if you are a very bendy 12 year old that weighs next to nothing, but a fully grown man not so good.

Keep up the good work.
 

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Just a thought...I believe that along with the camshaft you may need an upgraded EFI unit or a piggy back unit of some kind. Please keep us posted of your progress...
 

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Regarding the big bore kit: As far as I know there aren't any available for our 300's yet as its a relatively new model.
I would be cautious about this approach as the gearbox, drive train etc of this bike was originally designed for the 26HP output of the 249cc motor and is already now having to handle 30.4 HP which it seems to do fine, but to up the ante even more.... ?!

There is a 305cc big bore kit available for the 250R but it appears to make the engine unreliable from what I've read.
See post #24 of thread below if interested.

http://www.cbr300forum.com/forum/other-bikes/506-305cc-big-bore-kit-cbr250r.html
 

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Perhaps more left..

The CBR 250 R has the exact same bore/stroke as the CBR 1000 RR which has a Red line @13,000 RPM's. So in Theory the 250 R COULD be designed to achieve that RPM too instead of the 10,500 Red line it currently has.

So I will go out on a limb here and say that perhaps the 300 engine has the potential I believe to rev higher..much higher than it's tach posted 10,500 redline. Honestly I really wonder why Honda made this motor with 4 valves at such a low power peak...unless it is capable of much more.

Given that the R 3 is 321 cc..Honda could go with a 350 cc single..or a 350 cc twin....or better yet bring back the

NSR 400
 

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The CBR 250 R has the exact same bore/stroke as the CBR 1000 RR which has a Red line @13,000 RPM's. So in Theory the 250 R COULD be designed to achieve that RPM too instead of the 10,500 Red line it currently has.
That's interesting, I didn't realise that was the case. However... I think the issue with achieving those high revs is that one cylinder in isolation is a whole different kettle of fish to a four cylinder with regards to balance.

I'm just talking off the top of my head here so anyone feel free to correct me but I think the four cylinder motors achieve a better state of balance and smoothness because the cylinders balance each other out. Because of this they can naturally rev higher without shaking themselves to bits.
Whereas a single cylinder on its own despite maybe having a counter balance shaft fitted cant achieve that same state of equilibrium.

Having said that... I see some of the latest single cylinder trail bikes are pulling 12,000 RPM + so I could be wrong, it's happened once before! :laugh:

Regarding the peak power being at lower revs (8,500 RPM): I think this is to make the bike more user friendly to ride, esp for learners on their first bike. I'm glad they did, i personally don't like to have to wring a bikes neck all the time to get maximum acceleration out of it. Makes me tired and I'm middle aged now :D
 
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The CBR 250 R has the exact same bore/stroke as the CBR 1000 RR which has a Red line @13,000 RPM's. So in Theory the 250 R COULD be designed to achieve that RPM too instead of the 10,500 Red line it currently has.

So I will go out on a limb here and say that perhaps the 300 engine has the potential I believe to rev higher..much higher than it's tach posted 10,500 redline. Honestly I really wonder why Honda made this motor with 4 valves at such a low power peak...unless it is capable of much more.

Given that the R 3 is 321 cc..Honda could go with a 350 cc single..or a 350 cc twin....or better yet bring back the

NSR 400
Raising the redline only makes sense if you're building power or at least maintaining power to the current redline. As it is, power falls off rapidly after 9K indicating either valve timing or flow needs work before spooling any faster.

Better internals will likely be required to go beyond 12K. Piston velocity is getting pretty high at that point.
 

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That's interesting, I didn't realise that was the case. However... I think the issue with achieving those high revs is that one cylinder in isolation is a whole different kettle of fish to a four cylinder with regards to balance.

I'm just talking off the top of my head here so anyone feel free to correct me but I think the four cylinder motors achieve a better state of balance and smoothness because the cylinders balance each other out. Because of this they can naturally rev higher without shaking themselves to bits.
Whereas a single cylinder on its own despite maybe having a counter balance shaft fitted cant achieve that same state of equilibrium.

Having said that... I see some of the latest single cylinder trail bikes are pulling 12,000 RPM + so I could be wrong, it's happened once before! :laugh:

Regarding the peak power being at lower revs (8,500 RPM): I think this is to make the bike more user friendly to ride, esp for learners on their first bike. I'm glad they did, i personally don't like to have to wring a bikes neck all the time to get maximum acceleration out of it. Makes me tired and I'm middle aged now :D
I couldn"t agree more with the above statement. I Like the way the engine works and perhaps with higher revs..she may shake herself to bits..
 

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I just like that you shared your girlfriend with us, more pictures like that............ lol, I am of course slightly kidding. Great photo, can see the new user/motorcycle excitement on her face. Nice gear too, full leather jacket?
 

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Discussion Starter · #15 ·
The 305cc kit would be enough of a step up from the 286cc and to compliment with a hot cam and the mapping to make it work will be fun, but way down the road.
As for any inspiration, I'd have to say: If you want to add speed, add lightness.
 

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Discussion Starter · #16 ·
I just like that you shared your girlfriend with us, more pictures like that............ lol, I am of course slightly kidding. Great photo, can see the new user/motorcycle excitement on her face. Nice gear too, full leather jacket?
Yeah it's the Alpinestars Stella GP Plus R Leather Jacket. And yes, she is almost more excited about every mod then I am. lol
 

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Discussion Starter · #18 ·
Good stuff, have you seen my thread 'put your 300 on a diet'?

http://www.cbr300forum.com/forum/cbr300-general-discussion-forum/2458-put-your-300-diet.html

Ive reduced the stock weight by 28lbs so far. Noticeable increase in acceleration and improvement in handling esp 'flickability' when canyon racing or at track days.
I have. Ultimately I'd like to get some better wheels as that would do the most to effect the performance of this bike. But nobody makes something direct and Moto3 style wheels are a nice $4-5k easy. So we're aiming small. Pieces will add up.
 

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Yeah it's the Alpinestars Stella GP Plus R Leather Jacket. And yes, she is almost more excited about every mod then I am. lol
You are very very fortunate to have a girl friend that shares your hobby. Good for you.
 
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The 305cc kit would be enough of a step up from the 286cc and to compliment with a hot cam and the mapping to make it work will be fun, but way down the road.
As for any inspiration, I'd have to say: If you want to add speed, add lightness.
The 305 is based on the stroke of the 250, not 300. You actually get 349cc's with the kit on our engine, but without a custom piston it results in a roughly 13.8 compression ratio.
 
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