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Discussion Starter #1
is it possible to reach 30-32 bhp on the CBR250r?? :eek:
using whatever changes necessary ,except actually making changes in engine construction or damaging it??? using only performance upgrades or add ons??? :confused:

lets put our heads together and come up with ideas...and dont repost the same idea if already posted by someone...
here's mine:

Free flow exhaust
Sports air filter
 

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Discussion Starter #2
thats very basic right? wat more can we do?
 

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Larger injector, larger TB, ECU A/F tune.

You won't do much without pulling the head to be honest. The bike is a single cylinder that doesn't weigh very much. Pull the engine out (by hand with a friend) and pull the head, then disassemble the head and take it to a machine shop to have a thin slice machined off the mating surface with the cylinder sleeve/block. When you get it back from the machine-shop, take a dremel and (extremely slowly and carefully) match the ports for the intake and exhaust manifolds with the manifolds themselves and slowly open the runners into the head to match the opening that was just made (again, very slowly, you would rather do too little than too much). Clean the head thoroughly.

Next install Ti valves and stronger springs (if available, check the ones from a CBR1000rr as they should be extremely close) and some higher lift and duration cams. Also, if available, install adjustable cam timing gears. Set the timing after reassembling the engine with a tiny bit of overlap (exhaust stays open as the intake opens, drawing air in through a suction force).

Before reassembling the engine, take the time to buy new head bolts/studs, a new headgasket, and have the rings, bearings, and seals replaced as well as having the cylinder walls rehoned.

Reassemble everything and tune the A/F ratio accordingly to match the mods done. If possible, have the redline bumped to 12.5k rpm (or 13.5k rpm if you don't mind rebuilding the engine more frequently) to make the most of the top-end power that will be gained.

Make sure to have an open exhaust (no muffler or straight flow muffler with no catalytic converter), a free-flowing filter and intake assembly, a larger diameter throttle body, and a higher flow injector installed before tuning the ECU.

Break in the newly rebuilt engine, say goodbye to your Honda warranty, and enjoy your new, fast(er) CBR250r.

It would also be a smart idea to look at ways to improve the suspension (a la Racetech) and brakes (stainless lines or a dual front disc conversion off an older CBR250r model- the one that shares the front fork specifications as the new model).

Another way to speed up the bike is to drop weight, both from the rider and from the bike itself. The stock muffler and catalytic converter are heavy, around 20 lbs (or 8-9 kg if you prefer) and you will already be using a straight pipe so that weight will be gone. The tubing for your pipe could be replaced with Ti tubing shaving weight further. Loose the passenger footpegs and cover the rear brake fluid reservoir with a small piece of carbon fiber. Replace all body panels with carbon fiber if a replacement can be found (Tyga makes a good number). Replace parts with aluminum if a replacement can be found and the stock part is steel. Source an aluminum swing-arm and suspension components if replacements are possible (not sure if the stock pieces are steel, but the finish on them makes me suspect that to be the case. Loose the back seat in favor of a cowl made of CF (someone needs to come up with this ASAP). Replace the fairings with race bodywork if available, if not judiciously remove the inner plastic lining leaving a web pattern to drop some weight. And as a last resort, remove all body panel fasteners and hollow the shaft out with a drill press, leaving enough material to hold the panels in place without breaking. I estimate a drop of 30 lbs or more is possible from the bike. The rider, well, depends on how much you weigh now, and how much you want to work to lose weight, and if you empty your bowels before you ride. Your gear is another area, a lighter helmet and other gear (while still being protective) may cost a bit more, but if you are looking to cut weight, that is another area to look.

There are lots of ways to make the bike faster. However, the biggest question is, is the price worth the gain. Here in the states, I can sell the bike, take another 5000 USD and buy a brand new 600cc bike or a used literbike. The mods I mentioned would cost around the same price if not a bit more.
 

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There are lots of ways to make the bike faster. However, the biggest question is, is the price worth the gain. Here in the states, I can sell the bike, take another 5000 USD and buy a brand new 600cc bike or a used literbike. The mods I mentioned would cost around the same price if not a bit more.
Wow. You listed a slew of completely impractical and prohibitively expensive modifications.

Some of the parts you're talking about are not available and would have to be custom made. A lot of the modifications (and subsequent tuning and rebuilds) would require the budget and engineering of a satellite race team. Blueprinting a commuter bike's engine? Shaving the block to increase compression ratio? Custom cams, headers and swingarm for a $4000 bike? The time, effort and money wasted would be a huge loss compared to buying a brand new 600RR, a balanced and reliable package with a warranty.

drankurbaruah, I'm going to assume your bike is a commuter and not a track bike. A free-flowing intake and exhaust is the best you can do right now. A straight pipe isn't the best idea since your bike would be unbearably loud, no longer street legal, and without proper tuning, a loss of exhaust backpressure could actually lower engine output.

A more extreme option is to wait for a custom ECU for the 250R. Honda engines tend to run rich (to protect the catalytic converter, assumably) and a good tuning shop can get you a few horsepower from A/F adjustment even on a stock bike, or at least make the bike feel faster by manipulating the power band...

...but even this seems impractical. The CBR250R is a neat little thing, but you should measure power modifications with "dollars per horsepower" and think hard about how much your bike is worth to you.
 

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A larger injector??????? That would do absolutely nothing! It would just be prone to running rich and possibly flood out (even tuned properly) you will not be able to max the fueling capacity of a fuel injected single cylinder lmao. Not with out nitrous or forced induction at least.
 

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I know nothing about these engines but if it was a Sportser I'd say stroke it.
Maybe even bore the cylinder. Longer rod, shorter skirt piston with a domed top to increase compression followed by a fuel remap.

But please take what I say with a grain of salt. I know just enough in this field to be Dangerously Wrong :)
 

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That is exactly why I said what you quoted me saying.

The only reasons I could think of doing what I suggested are if you wanted a 250 because of a country's licensing restriction for new riders, or you just wanted to try something new and untested. There is also the chance that someone would want a middle performing bike to split the difference between the 250r and the 600rr for a track learner bike.

Personally, before I do anything to mine I will have something else as a daily ride and fun bike. A 675 Daytona is currently holding number one position at the moment, but I will wait until I have had the 250r paid off for a few years and some other financial matters taken care of.

The reason I posted what I did was simple. He asked how to make power on the 250r. The answer is simple, you un-do what Honda did to de-tune it from the factory, namely raise the compression ratio and the redline, open up the exhaust and intake, and tune for a leaner A/F mixture. Basically matching the setup on a single cylinder of the 1000rr, which shares the same specs as the 250r.

In regards to the straight-pipe losing back-pressure, yes, you will lose most of the low-end grunt, but you will gain a lot of top end pull, at speeds where the 250r needs a bit more pull (namely 70mph and above). You also lose 20 lbs of metal from your bike. As far as the legality is concerned, it depends on where you live. In my area, a straight-piped bike is par for the course and would not cause an LEO to bat an eye. In a more hippie-oriented state like NJ, NY, IL, or CA, LEOs might give you more grief over the modification.
 

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A larger injector??????? That would do absolutely nothing! It would just be prone to running rich and possibly flood out (even tuned properly) you will not be able to max the fueling capacity of a fuel injected single cylinder lmao. Not with out nitrous or forced induction at least.
Bump the compression to 12.5 or 13k and the larger injector is an additional precaution so you don't grenade your motor when the stock one can't provide enough fuel and you run lean.

It would do absolutely nothing otherwise, except waste money.
 

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I know nothing about these engines but if it was a Sportser I'd say stroke it.
Maybe even bore the cylinder. Longer rod, shorter skirt piston with a domed top to increase compression followed by a fuel remap.

But please take what I say with a grain of salt. I know just enough in this field to be Dangerously Wrong :)
The beauty of this engine design is that it is very oversquare, meaning its bore is much larger than its stroke. This is just asking for a higher RPM redline, as it is completely capable of sustaining the higher speed based on its geometry. It may need some stronger fasteners and stronger components in general to sustain the additional forces, but not likely. Though a stronger set of studs for all the lower rotating assembly and a rebuild during the process certainly couldn't hurt the situation.
 

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Some ppl have obviously bought the wrong motorcycle.. It is a cheap effective Thai made sporting commuter.. just enjoy it for what it is.

Spend the money on a weight loss program, riding lessons, or track days.
 

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Some of the responses here are apalling. Amontgomery, you were on the right track.

The head is where all the hidden power lies. We have managed to double the power of a naturally aspirated Honda engine by bumping up the compression, porting the head, working on the combustion chamber and various other tricks. It is not insignificant, and neither are the costs.

Let the people decide what they want to spend the money on, shall we? Not everyone is a fat 300 kg slob who doesn't know how to ride a bike properly.

Assume that there might be restrictions during races which might mean that someone with a smaller displacement motor gets an advantage.
 

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Some ppl have obviously bought the wrong motorcycle.. It is a cheap effective Thai made sporting commuter.. just enjoy it for what it is.

Spend the money on a weight loss program, riding lessons, or track days.
Exactly! Better to ride a slow bike fast, than a fast bike slow. Master the 250cc then move up to a 600cc. It's a big jump so be ready for it. I hear about dudes all the time that can whip a 250 around any corner and overall handle it like a pro.... so they buy a 600 and dump it the next day. It's more weight, more ponies, and more to pay attention to.
 

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Some ppl have obviously bought the wrong motorcycle.. It is a cheap effective Thai made sporting commuter.. just enjoy it for what it is.

Spend the money on a weight loss program, riding lessons, or track days.
Why would we have a a CBR250r "PEFORMANCE" section if people didn't want to make what they have faster, stronger, lighter? Some people want to make the best with what they have, and it is these people who come up with the new ideas that other people, who originally scoffed at them, benefit from.

Put someone on a 250r who knows how to ride very well and weighs a healthy weight. They will be far more capable on a twisty course than they would on a larger bike. Drop a bunch of weight from the bike, do the modifications to the engine I was suggesting earlier, and put the same person and tuned bike on the same track. He/She will do much better than before, how much better is directly proportional to how much better the bike performs, assuming the rider does everything the same.

The new 250cc class in Motogp should show what a 250cc, four-stroke is capable of. And the answer is far more than being simply a commuter.
 

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Some of the responses here are apalling. Amontgomery, you were on the right track.

The head is where all the hidden power lies. We have managed to double the power of a naturally aspirated Honda engine by bumping up the compression, porting the head, working on the combustion chamber and various other tricks. It is not insignificant, and neither are the costs.

Let the people decide what they want to spend the money on, shall we? Not everyone is a fat 300 kg slob who doesn't know how to ride a bike properly.

Assume that there might be restrictions during races which might mean that someone with a smaller displacement motor gets an advantage.
Exactly.

Also imagine that some racing club has a special unlimited class for sub-250cc bikes.
 

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Holy herp-derp batman. CAPS LOCK SHOULD BE USED SPARINGLY

Why the **** does it matter to you what people spend their money on?

And for the record, the modifications I suggested, other than the parts, would be fairly conservatively priced. Got access to a machine shop? You can have the compression raised. Find a tuneable ECU and you can tune it yourself. All the labor could be done (with the exception of the head machining work) by the owner if he/she has even the slightest bit of mechanical knowledge and a place to work. Honing the cylinder walls and rebuilding the engine would be relatively cheap work to do as the cost would be in the tools (if you already have the tools or plan on working on many engines, that's not an issue)

The cost is in the ECU and dyno time, the rest of the procedures are free as you can do them yourself.

Adding lightweight parts can get expensive. We all know how much carbon costs. But that doesn't mean you have to do everything to cut weight. Every little bit helps.
 

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Compression, cams, competition valve job, minor headwork, pipe, fi-tune, velocity stack. it will make 30 hp no problem. Mine makes 27.5 with no internal mods. The class i race in doesnt allow motor work. but im sure you could get there reliably.
 

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But I guess I can't be too surprised at these kind of responses. I have seen threads asking how to remove stickers, fill up with gas, and put air in tires. With this kind of mechanical knowledge and skill, some folks should just stick to buying pre-built performance packages and having someone else do all the work for them.

Some people probably couldn't install an aftermarket exhaust even though there are a grand total of 2 bolts to remove, much less disassemble a head.

On the other hand, if a person can do the work without paying someone to do it for them, many of the modifications I list should be no issue.
 

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Well I hate to say it. but if you wanted an easy 30-32 hp you should have bought a ninja. A full pipe ($550) and a jet kit ($90) and you will get 30+ hp when properly tuned. Thats at the wheel of course.
looks like 28 hp is about as far as you are going to go with bolt ons.
Heres a ninja 250 dyno sheet from area P
 

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