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My plan for a CBR125R 2008

Discussion in 'Modifications and Projects' at netrider.net.au started by drewzor, Mar 14, 2008.

  1. I was waiting three cars behind a set of red lights, a guy on a R1 and myself took off as the lights went green and we troll through our gears before being stuck going up a hill behind someone in a camery.
    I notice a scooter keeping up with us with no problems at all. I started to think... whats the point of anything above a 125cc for around here?

    Maybe on the open road I can see the point or if you want to hit 120k in 5 seconds? Really.. you would pay 7k + for that feature.. FThat! I would only ride like that maybe 5 times a year..
    These bikes can do 140, takes most of tuesday morning but they do it and you can enjoy riding a bike to its limits without killing yourself. For me I think it will work well.



    So I have decided to buy a CBR125R and plan these mods apon purchase.
    Shark exhaust
    30mm lower seat padding
    rear seat cowl.
    Upgrade tyres from 100/80 17 to 130/70 17 & 80/90 17 to 100/80 17

    This is how it should look.
    [​IMG]
     
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  2. Looks good.

    Sure for around town you really don't need more than 125. If I had to do anything more than 80 though I wouldn't be so keen. Given that you can only legally do 90 when you're on red Ps though, in theory it shouldn't be a problem.

    Except for if you intend on doing longer day/weekend group rides, they're just not practical without slowing the group down. But otherwise should fit the bill, the light clutch would be bliss in traffic.
     
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  3. Well...it's an interesting idea :shock: Far be it for me to discourage, as all riding, on any bike imaginable, is just fantastic, but....

    Cowl, padding, easy and cheap fixes....if you needed/wanted to

    Exhaust, well, it might make it louder, probably wouldn't make a difference powerwise that you could feel in person, and would cost a bit.

    Tyres - can you change those sizes on the standard rims? If not, then you need rims as well, are the brakes going to fit? Probably not, need to make adapter plates, spacers etc.....more effort than it is worth?

    Then, you have a machine that can do 140, as long as there is no hill, no headwind and you are a featherweight. Probably find most days, it tops out at 110 or so.

    But having said that, they are cool looking bikes, and if it floats your boat, why not? Bargain price too :)
     
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  4. Yeah, I'm focusing on asthetic's cos its pointless trying to performance inhance a 125cc.

    I'm told so far that these are the absolute largest tryes you can fit on it, they are of the same spec as the YZF125 Yamaha and shouldn't require new rims.

    Exhaust is a must. They sound just like my fathers lawn mower and I can't live with that. This system makes it sound fatter and gives 10% performance gain...which should offset the size tyres.

    Why fat tyres? cos it will make it look good.
    cowl makes the bike look bigger to suit the tyre size
    seat is lower because I'm told with fatter tyres I will lose nimbleness and lowering center of gravity should restore this.
     
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  5. Speed is not the issue in the city or in moderate traffic.

    The issue with negotiating in traffic is your ability to 1) maneouver and 2) call on acceleration when needed to avoid or take opportunity in traffic.

    I ride an R1, and have also ridden a scooter.

    The R1 whilst wider and not always good to filter with gives me far superior acceleration management.

    On a 125cc you will not have a problem slowly getting to 50, 60 or 80kph.

    It is when you release the throttle (thereby dropping RPM) and then needing to get back to that torque curve in order to either change lanes (to keep up with that lanes traffic) or shoot / thread through a gap that the 125cc will fail you. Why? Because the engine will have a large lag time in bringing the scooter or bike back up to speed.

    This can be the difference between being rear-ended by another car and performing a quick over-take manouver.

    I have been in situations where buses have changed lanes, truck cut me off and braked etc. etc.

    If I was on a bike under 600cc, it would have resulted in me being trapped in nasty situations.

    I still think for commuting and general travel, larger bore bikes are much safer (assuming you use it wisley).
     
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  6. This is a valid point, I have experience what you are describing on my partners scooter. While crusing in traffic, someone starts to merge, you cant slow down for fear of going under the truck behind you so you twist the wrist and you hear brrrrr BRRRRRRRRRRRR and you start to consume inches at a rapid rate...... hahaha

    I would argue that this experience is a lack of road craft rules being applied but we all find ourselves in the situation at some point.

    So then the problem is torque?
    Having reluctantly read some performance suggestions for this bike I found that you can change the sproket (rear smaller front bigger) to allow
    for a greater delivery of power.
     
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  7. The better solution would be a Motard with a large single cylinder engine.

    Changing the sprockets on a CBR could improve acceleration, but it'll also reduce the bikes top speed and increase revs at cruising speed. That is good for improving throttle response at speed without having to drop a gear, but will also significantly reduce engine life.
     
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  8. Reduces engine life?
    Sorry I dont understand, wouldn't this reduce the load on the engine?
    eg; 5000rpm produces say 60km amount of speed on flat
    Install sprokets
    3000rpm produces 60km amount of speed and 5000rpm now produces 80km.

    This means a greater percentage of its life is running at lower revs to produce the same power.

    Maybe if you were throttling its neck at 110km smacking the arse of the red line I could see how it would be damaging but 90km is the most I'll ever do anyway..

    or do i have this back the front?
     
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  9. Back to front.

    What you describe is what would happen if you put larger sprocket on front and smaller on the back.


    What was suggested was a smaller on the front and a nice big dinner plate on the rear, which would give better acceleration but sacrifice top speed - which is already quite low.

    You can run the numbers (cbf right now it's officially the weekend) and most likely you will lose only a few % of the top speed for a small gain in acceleration which would make it worthwhile on anything over a 250 (inclusive) but still not exactly my cup of tea on a 125..... just turbo it instead :p
     
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  10. You have to smash through the gears in a hurry as it is, bumping up the rear sprocket would make things a pain IMO... first gear would be good for 5kmh
     
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  11. Ok, I'm leaving the gearing stock.. like I said in the first place "There is no need for a bike bigger then a 125cc" (for me at least)..

    So back to the original topic which is aesthetic mods for a CBR125R

    Here are some more I have chosen, New rubber handles and graphite tips.
    Better looking mirrors mounted from the front fairing and Iridium look screen (screen not shown)
    [​IMG]
     
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  12. Sounds good. Some other things maybe.. oggies, replace levers (or just paint them) and have them the same colour as bar ends / oggies / windscreen screws, etc. Fender eliminator
     
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  13. Don't know about the fatter tires. It could screw up your handling pretty bad as the bike wasn't designed for such large tires....
     
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  14. +1
     
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  15. This is the motorcycling equivalent of buying a Hyundai Excel because you don't need anything quicker/bigger (fair enough so far) and then blinging it out with fat tires, colour coded gear knob/pedals/mirrors and a big ass spoiler.

    I swear motorcyclists are all ricers at heart. :roll:

    Oh, I forgot neons! A cbr125 definitely needs neons.
     
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  16. has anyone here ever had excessivly large tyres for their bike?
    If so how did it effect it?

    Personally I can't see how it would effect this bike too much negatively. Heaver steering yeah but just like a car it should improve stability (besides wet weather)

    this is a 120/80 17
    [​IMG]
     
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  17. Tires that are too large for the rim simply pinch in, making the tire taller and skinnier. This changes the geometry of the bike, and you still dont get a tire that LOOKS bigger. Further to that, and I havent done the sums, but I believe you dont get a larger contact patch either. You've got a greater surface area of tire, but are using less of it (and can't use the edges at all) because of the profile.

    The only time I would use an incorrectly sized tire is to get a better compound, if there was nothing available in the correct size.
     
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  18. Changing sprockets does not allow for a greater delivery of power. There is hardly any there to begin with, and changing the gearing will only make things worse.

    If you increase the front sprocket or reduce the rear you will lower the revs at any road speed. Its a bit like adding a seventh gear and taking away first. You will consequently have less acceleration, but possibly, if the bike will still maintain 90 kmh on the flat, it will rev lower.

    However the poor thing will be running with the throttle pinned to the wall.. You just cannot get more speed or performance out of a bike with 13 hp by changing the gearing!

    Making the front smaller or the rear larger will increse the engine revs at any road speed, and slightly increase the meagre acceleration that is already there. That's a bit like having an extra gear below first, and sixth ends up being closer to fifth. For what point?

    Cheers

    Trevor G

    PS You will find that a standard bike will need to be dropped back to 5th in a strong headwind or uphill, anyway. Maybe even to fourth...and that is witrh it in standard trim.

    PPS Larger tyres will just look pathetic. Bigger tyres do not help power or handling at this level. In fact larger tyres are not a motorcyle performance or dressup feature unless you want one of Deus' sand-gropers...and that is enormously big!


    BTW Check out the shiny chain on that 125

    When will people learn to lube the chain lightly and often?

    If it goes at all shiny you have lost!!
     
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  19. Where would you get this '30mm lower seat padding '?
     
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  20. Bread knife, sander and a staple gun is the cheapest way.
     
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