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more grunt for cbr250rr

Discussion in 'Modifications and Projects' at netrider.net.au started by sam_ye, Jun 26, 2009.

  1. hey guys
    i've had my babyblade for a month or two now
    am confident with everyday riding and am now looking to play around with it.

    i've been hunting around for simple and cheap mods to do on the bike and have returned such results as after market air filter and enlarging the airbox, and new sprockets. was wondering if you guys can give any advise on doing those mods and other work i have to do due to those mods.

    i'm also thinking about taking the silencer out of the exhaust. now for some of you, you'll b thinking "hold on, this joker was onli rescently complaining about the noise level of his bike". i know i was, but it was more the fact that atm my bike is winey like a biatch. hopefully the lack of silencer will make it sound meatier. what do you guys think?



    lastly, any other cheap simple mods you guys can think of? as i'm not exactly mechanically minded myself, complicated stuff will most likely result in the destructiong of a perfectly good bike.
     
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  2. The quickest way I think to make it faster than usual is ride it to a cliff and push it off! It's a 250, if it was meant to be fast, everyone would ride one.
     
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  3. There is stuff that can be done, Exhuasts, re-jetting etc.

    Or saving the money that it would take to getting a little more speed and put it towards a faster bike when your off restrictions.
     
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  4. You're wasting your time & money. Live with it for a year, ride the wheels off it, get a real bike & feel real powaaah! Without spending thousands of dollars & hours of time you'll get bugger all real performance.

    Cheers! :grin:
     
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  5. Err enlarging the airbox may reduce power. In NA engines quite a lot of time is spent designing the intake tract for proper intake resonance.

    Im going to go with the flow and say dont waste your time or money. Honda already pushed plenty of power out of that 250cc, its time to get a bigger engine.
     
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  6. 160hp/L from factory, naturally aspirated, yeehaw!
     
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  7. They are putting out about as much as you're going to get from a 4 stroke 250cc

    There's precious little to be gained beyond more noise.....from any of those mods.

    Buy a larger lams bike if you want more power/torque.

    Otherwise, now get the hang of throwing the thing around corners, the bike is likely to still be faster than you are :)
     
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  8. if you are still on restrictions then i doubt you've out grown your 250, as everyone says. i know i haven't.
     
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  9. thx for the tip guys. but i have already decided not to spend thousands and thousands on my current bike. i'm not gonna do nething crazy like boring out the cylinders or flushing everything thats flushable and rebuilding the engine (may clean the carbie once in a while). but i do plan to keep this bike until i finish uni due to the lack of funds coz i'm hardly working during uni

    i'm just talking about simple stuff like less restricting airfilters, different sprockets for better acceleration. u no, cheap stuff. don't even think i'll go touching the exhaust headers.

    btw guys...wot about the silencer removal. is the silencer removable or do i havta bash it?
     
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  10. My brother has a baby blade and the biggest difference was changing to a larger rear sprocket.
    It made a very noticable difference to the bottom end-mid range. From memory he only went one tooth bigger on the back but I was suprised at how much quicker it felt. Don't bother with air filters. Exhaust system can make a bit of difference but then you have to factor in jetting and getting it tuned properly and it still won't be as noticable as the sprocket which will only cost you around $50.
     
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  11. It's not easily removed as we had a go at this. In the end it was easier just to buy a performance pipe from ebay. I'd seriously advise against trying to remove it.
     
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  12. 250cc can go fast, but only in the corners (comparitively).
    Yours is a relitively high reving in-line 4, most of it's power will b up the top.

    First thing is to suss out any restrictors it 'might' have (Some 250cc bikes shipped in have stuff like early throttle stops & restrictor plates here & there).
    Next is to make sure you're runnng new plugs/leads, replace all the filters (even the fuel filter).
    Gearing might help. I had a 748 Desmoquattro & had a problem staying with larger capacity bikes at places like Phillip Island. I reduced the ratio (geared it down) on the rear sprocket by 2x teeth & got that extra pull out ofthe corners that 1000cc bikes had all over me. Brought the gears closer together (slightly) too but did not pose a problem out on the road - improved my fuel economy too (??).
    Goggle mods for your bike on the 'net. Tuning might liven the engine up, simple stuff like carb (re)jetting & airbox mods.
    Important not to go off modding anything 'before' the engine - like airbox, fuel system etc untill you make sure you can tune to suit. (like opening up the airbox will mean maybe more fuel with jetting to compensate).

    In the end, your bike, being a 250cc will benefit more from sticky, racey tyres (for its type, no 180 rears..), suspension mods , brakes refurbishment , that sort of stuff.
    Use it's light weight & manuvability to it's advantage, don't be frightened to rev it. Change engine il often. Do some track days (maybe Broadford or Winton - oh you're not in Vic?).
     
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  13. Get decent sporty tyres, will help you go fast :)

    -1 front sprocket for added acceleration(will revv higher for same speed though)

    Put in new air filter, stick an ebay $100 cbr250rr muffler on it and give it a good service - if the front end is spongy it'd be worth getting new fork springs and oil.
     
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  14. hang on a sec...marx, so gearing down by 2 teeth means reducing rear sprocket by two teeth? coz ross is saying add more teeth to the rear.
    so is it more on rear and less on front for greater low end pull?

    and excuse the noobness here, but wot is jetting?

    i hav two for new air filters. is it a gud idea to go a less restricting air filter? or does that mean i havta balance the carbs to get the correct fuel/air mixture?

    as for the exhaust...no1 seems to b in favour of just bashing out the silencer. though i think one for 50 dollars from the wreckers for me to play with is the cheaper option than 100 dollars one from ebay. i hav read in other places where people drill holes into the muffler to open is up...ne tips on how to do that?
     
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  15. With a carb bike if you change intake (filters) or exhaust you may have to rejet the carbs as increasing the flow in/out will change the air/fuel mixture - probably making it leaner. So what you have to do is pull the carbs apart and change the jets to allow more fuel flow to get it back to the correct A/F ratio.

    You would need to find people who have done similar mods and see what they have rejetted to, otherwise you are going blind. I've rejetted my bike several times myself and my particular bike is very easy to do, and there is heaps of info on which jets to use.
     
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  16. ok cheers
    any1 with any experience in cbr250rr jetting??
    the lack of silencer would chang ethe flow out i assume. so that means i'm better off doing the exhaust and the air filter then rejet the carbs?
    and i'm still seeking advise about the exhaust...i'm deff not going n aftermarket one off ebay or w/e. just wondering if there r ways to tamper with the stock exhaust.
     
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  17. The CBR250RR has the potential for a bit more power, but honda doesn't make it easy.
    Despite what people say, there are a couple of options.

    The 1994+ CBR250RR's were limited to 40ps and the prior ones were limited to 45ps. They are limited by cam timing, porting, ignition timing retard and the carbs are different between the two. They apparently start cutting ignition at 17,500RPM or something, so you've got a bit to play with.

    You can get it ported and the cams reground, but you run into a problem with the CDI which retards the timing around about peak power to keep the output within japanese spec. People have looked for alternative ignition units, but you'd need one which goes up to ~20,000rpm. Other people have built their own fuel injection system, but I believe that was never finished.

    I think one of the guys on the CBR250 forums has a honda race cdi which lets him rev higher (not the eBay ones), but I don't know how you'd get one.

    So, uh, its probably not worth it. Just get the usual done (jetting/dyno tune). Perhaps a better air filter.
     
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  18. Yes, it is best to do intake/exhaust/internal modifications as a "package" and retune after. Unless you want to retune after one item is done, and retune again after the second item.

    Now for the subjective bit:
    I'm not big on mufflers that have had a "bafflectomy" to remove/destroy the internal baffles. They usually sound raspy and tinny to me.

    A straight-through glasspack muffler would be ideal as the fibreglass packing (or ceramic packing) absorbs the tinny high frequency sound and leaves you with the low frequencies only.

    Having said that, IMHO the CBR250RR doesn't that great with an aftermarket muffler. Prefer how they sound stock. (Unlike the VTR250, which sounds pissweak when stock but adopts a pretty meaty Ducati Monster V-twin with a glasspack) But that's just my opinion. :)
     
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  19. all the things megaphat mentioned sounds awesum...but too complicated and most likely too costly. i like the idea of just increasing airflow then retuning the carbie to suit...then sprockets for a down low pull...money is n issue here. cheap is the way to go for me atm

    how much is the glasspack? c a muffler from the wreckers will cost me like $50 and i can experiment with that. has ne1 done it b4? wot do they think about gutting their stock cbr250 exhaust?
     
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  20. Seriously....on a cbr250....you will spend hundreds on jetting, dyno time, exhaust etc....for very little gain ie 3-5hp at the rear wheel if you are very lucky, more likely you will lose power or sacrifice bottom end to achieve that tiny gain. (or you will spend next to nothing drilling the shit out of the airbox/exhaust and bolt on a pos exhaust, and have an expensive shitty looking/sounding 250)

    Honda has some idea what it was doing, you don't get 40-45hp (reliably!) from a 250 by purposely making a restrictive airbox (to the detriment of power/flexibility), putting the wrong jets in the thing or the wrong exhaust.....these are the cheapest easiest things Honda could have "fixed" to achieve more power.

    Spend the money on a track day, good tyres or gear, save it for the next bike, coke/hookers.......anything.... :LOL:

    This is a well trodden path most of us have been along (people who have been stuck on 250s), you can't get blood from a stone :LOL:
     
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