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You can get mods covered by insurance companies over here, but you must tell them about them. Some mods (not for road use exhausts etc.) or any mod that will prevent your bike from passing a MOT test, can render your bike "unroadworthy" therefore invalidating your insurance, so that if your bike gets totalled by another vehicle, the other party's insurance company can refuse to pay out.
 

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Discussion Starter · #24 ·
Hey thanks for the input my buddy said the same thing when he saw a cross section of the motor.
 

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Porting will yield approximately zero horsepower improvement. You're more likely to mess up the torque characteristics and idle than add more than .2 hp.

As for polishing, it will yield exactly zero horsepower.
To add to this:

Porting (enlarging) won't just yield approximately zero... it will actually more than likely reduce power overall.

Make the ports 20-30% smaller, thereby increasing velocity (rather than reducing it) and you will see favorable results on the dyno.

Bigger isn't always better, even if it's what the "common" folks say is common sense. Most of the "common folks" who talk about needing bigger ports have not measured their changes in a scientific way- usually they change 3-4+ things at the same time and then say "wow, i'm glad we ported and polished"... when in fact if they'd stepped through the build one part at a time and tested each thing individually (very difficult with an engine) they would probably (usually) see a reduction in power (or at very least, unfavorable changes to the power band) as a result of the port enlargement.

Reasons are very simple, actually- the actual intake phase (when the valve is open and the piston is moving downward) isn't the most important part of the "air charge" process. Yes, it's important to get a good amount of air in there- but almost every engine in the world has a slight sort of "overlap" between when the valve is completely closed and the piston is moving back upwards.

If you make it to where there's less vacuum on the intake, you also make it where there's less back pressure during this overlap. I.E. it will blow the air back up the intake runner just as easily as it sucked it in.

Once that air/fuel gets pushed back up- it gets more fuel added to it, making the next intake stroke too rich... To some degree, depending what the desired mix was in the first place, this ends up making even less power.

There's far more to it than this simple explanation... but actually having SMALLER intake ports is usually the recipe for better power, not bigger. It's not a closely guarded secret, it just goes against the blind acceptance of "common sense".

Folks, I know NSU doesn't produce a lot of fanfare with his messages, but he is a smart cookie- definitely more people need to pay attention to the things he says... and if ya don't understand what he says, ask questions. Ya might learn something. ;)
 

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Rando I'm an old guy with FAST bikes with lots of POWER :mad: BUT MAN I'M WITH YOU :D fix the bike the way you would like it , RIDE IT AND HAVE FUN :rolleyes: :eek:
by the way my CBR250RA has Race Tech suspenison Frt & G3-S SHOCK W/REMOTE RES,full SS YOSHI exhaust , DYNOJET DFC , Galfer steel brake lines & wave ROTO ;) so like I say GO FOR IT :)
 

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Hey if Rando wants to juice the box up a little why?? knock him. Some of us like to get a nut off doing things like that. Rando let the rest of us that want to know how you did on it. The thrill is doing something that either hasn't been done before or just to make it a little better for the rest of us!!!!!!!!!!!!!!!! :)
 

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Why waste your money on the 250. You should of bought a 750
Because he can and he wants to, this is cbr250.net so why not answer his question instead of saying something that is common knowledge...
I have a whole garage full of toys everything has been tinkered with and a lot more pleasurable to drive and ride something you have tweaked yourself
Tweak it mate and enjoy.
 

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Because he can and he wants to, this is cbr250.net so why not answer his question instead of saying something that is common knowledge...
I have a whole garage full of toys everything has been tinkered with and a lot more pleasurable to drive and ride something you have tweaked yourself
Tweak it mate and enjoy.
Holy thread necromancy Batman!
 

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Haha Yeah just noticed that I've been one this site for 3hrs and I'm done already was to much school yard bullshit
My Australian friend, I new here in the forum too. You will find here a lot of useful information. I'm already saying thank so much for the things I learned here, and are not accessible in any guide or book.

Get another tip - Consider the group dynamics: The forum is international (multicultural), and the largest group is from USA (The founders?). CBR250R sold in the United States and Canada with the "EVAP Canister". The forum is intended only for discussion of the CBR250R model from 2011 and on. You will find here people of all the ages. The forum has existed since 2011, and its first years were the most fruitful, even today it is impressively active. What you do if the information you find here is at your own risk.

Maybe you want to teach me something new now? and the most fun is that people also upload pictures here about the topic they are presenting.

Bottom line: What are you looking for? Type in the keywords in the search window, and you will see which of the results might interest you. Even on an old thread people will respond and answer to you, just like what is happening to you now (It is not acceptable to open a new thread on a topic / thread that already exists). You will find a great deal of technical information, along with personal conversations, but personal conversations are not the main point here.
Just saying, I'm not here to educate anyone.
 

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If you want a fast bike, why don't you buy one, instead of trying to make a slow bike fast? It'll be much cheaper and easier in the long run. ;)
I'm keen to know what gains can be had from head and cam mods. Yes, its cheaper to just buy a bigger bike but I like the option of pick it up and ride away after a spill (I've done this). Also an improvement in power to weight ratio combined with magnesium wheels means you'll beat a bigger bike off the line almost every time. Sure, they'll blast past you in first gear but they're using alot more fuel to do this.!!!
 

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There's no substitute for cubic dollars! Well, let's compile shopping list on what it takes to double HP NA way:
  • stroker crank
  • big-bore cylinder
  • forged high-comp big-bore piston
  • titanium con-rod
  • bigger back-cut valves (stainless intake, inconel exhaust)
  • fully radiused copper-beryllium valve-seats
  • serious head porting & polishing
  • custom cams
  • custom intake
  • larger throttle body
  • larger MAF
  • larger injectors and pump
  • custom exhaust
  • aftermarket programmable EFI system to tie all above together
  • machine shoppe time and labour to install all above
  • lots of dyno-time tuning above package
U$20-25K is my estimate and you may not even double HP. You're basically converting CBR250R engine into NSF250R version. Might be easier to buy NSF250R engine. Although I don't think Honda will sell one to just anyone. Might need to buy NSF250R for U$45K.
 

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Can you really fit a turbo on these bikes? I'd like to see that and know how much it costs.
You can turbocharge ANYTHING! Comes down to cubic dollars and how much fabrication and programming skills you have that you can do yourself vs. farm out to engineering shoppes. Lots of custom cutting, welding, wiring, programming and dyno-tuning.

For example, there's guy that built turbocharged barstool using Honda 160cc single and SDS-EFI system (typically used on Lycomming aircraft engines).




This is turbocharged intercooled scooter with NITROUS shot added!


Here's guy that chopped his FZR250 engine in half due to racing regulations. Then added turbo to bring power back up. Ecotrons is crappy EFI system BTW.

Here's another that converted his carbureted Ninja 250 to EFI then added turbo. Then built his own dyno to tune that turbocharged Ninja 250. Many, many Ninja 250s have been turbocharged gettjng 50-60bhp.

I'm working on turbocharged NSR250 track-bike with RZ350 engine. Target 100bhp and 300lbs wet.

So again, ANYTHING can be turbocharged, comes down to pocketbook and access to fabrication and tuning skills. Here's shopping list:

  • Garrett GT0632SZ , don't fall for marketing idiots pushing VZ-21 turbo
  • custom exhaust manifold to turbo
  • custom exhaust after turbo
  • intercooler
  • custom intercooler charge pipes
  • custom piston, 9.0-9.5:1
  • stiffer valve springs
  • larger injectors and pump
  • custom intake
  • aftermarket programmable EFI system from Accel DFI, AEM EMS, Apexi PowerFC, Austronic, Autotronic, Electromotive TEC, EMtron, FAST, FiTech, Haltech, Holley, LinkECU, Megasquirt/Microsquirt, MoTeC, ProEFI, SDS-EFI, Wolfe 3D, etc. (stay away from Ecotrons)
  • dyno tuning to tie it all together

U$2k to $10k depending upon how much work you can do yourself. That's not bad for 30hp gain. That's $67-333/HP-gained.

Way, way better deal than all bolt-ons you can slap on bike such as intakes, filters, "chips" and flashes, full exhausts and even cams. Those give measly 2.5hp increase for $1000+ for $425/hp-gained. Far cry from $67/hp.

Not to mention riding bike with +2.5hp feels extremely disappointing compared to bike with +30hp!!! :)



BTW - this is just start, there's no limit to turbocharging power!!! You can even go +45hp if you wanted. Now you'll need new valves and forged conrod. Add +U$1k-5k to build cost.
 

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found actual CBR250R with turbo. No details though

Without intercooler, it limits how much boost you can use. Probably around 7-8psi for +12bhp gain. Almost not worth it for effort & cost.
 
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