40% power gain on Ninja 250? Yeah?

40% power gain on Ninja 250? Yeah?

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cyberface

Original Poster:

12,214 posts

207 months

Friday 18th June 2010
quotequote all
Power is not the next item on my Ninja 250 project bike - braided brake hoses and suspension are. I figured that I'd get the handling as good as possible before messing with the engine - because I don't want a LOT more power anyway (otherwise I may as well have bought a faster bike).

However in my internet searches for ways to make the little Ninja *lighter* (as in the Chapman approach to speed - to go faster, add lightness), I came across this Sport Rider article:

http://www.sportrider.com/features/146_0904_2008_k...

which featured a Ninja 250 souped up to break the 4-stroke 250cc land speed record, by the looks of things. They claimed the Ninja 250 puts out 25.6 bhp and 13 lb ft torque in standard form on the dyno. This is slightly lower than the claimed 32 bhp, but the article is about the US-spec Ninja, which retains carburettors whereas my UK-spec bike has EFI. Still, I've got an indicated 104 mph out of the bike, whereas the article claims a maximum 98 mph, so given the usual over-reading of on-bike instruments, I doubt my bike is producing anywhere near 32 bhp.

Reading the article, with no capacity increase but an increase in compression ratio and some (presumably extensive) head work, they managed 35.92 bhp and 16.79 lb ft, with the power produced at 12,200 rpm. Since my bike already redlines above that (13,000 rpm)… what's the story with the stock engine, then?

The special engine built by the 'Sport Rider' guys in the USA claims 40% more power than stock, which is a HELL of a power increase on a nasp engine that already spins pretty damn high.

Does this sound at all realistic? There's no increase in rev limit, and nothing appears to have been done to the engine to make it sound like a grenade or 'race' engine that requires 100-mile rebuilds.


Of course, it could simply be that the Ninja 250R engine is under-tuned in order to pass the 33 bhp (or is it now power-to-weight?) regulations for A2 licence holders (regulations which are similar in many more countries than just the UK), and getting more power for full licence holders isn't a big deal. But I've not heard of any common bolt-on kits, and regardless of the article's claim that the bikes aren't widely raced (they are, in the USA, oddly enough), AFAIK the race series is a standard-bike type formula to keep costs down, a form of real 'budget racing'.

In the course of my project research, I've found that 'adding lightness' is pretty much the most expensive way you can improve a bike hehe which is pretty typical! My enquiries to the carbon-wheel chaps resulted in an apologetic 'no chance' - their thinnest road-legal wheel is built for a 180-section rear tyre (i.e. all you supersports and superbike chaps out there) and whilst my enquiry was based on seeing a GP 125 (Bradley Smith's bike) using their wheels, the race wheels may theoretically fit but would not be road legal.

And carbon wheels, whilst being ultra-cool, are expensive. Not that I'm overly bothered, since I like having something different and I knew as soon as I took delivery of the baby Ninja that it'd end up becoming one of my mad projects biglaugh


Part of the project is to end up with a road-legal, emissions-compliant, low-top-speed but high-acceleration, super-handling corner monster. Basically like an Aprilia RS250 but four stroke, reliable, and possible to ride and use regularly without being stolen. Modifications hence must be subtle in looks. IIRC the Aprllia RS250 had around 60 bhp but I don't need that much - I don't want a top speed anywhere over 115-120 mph, as per the original 'Lotus Elise of motorbikes' concept.

The sticky tyres have given monstrous grip, but have shown up the inadequacies in the suspension straight away. I'm hoping the flexiness and nervousness is down to suspension rather than requiring new swingarms or other major mods, but always was expecting to replace the rear shock with something high-quality. A good rear shock will also reduce weight, which is a good thing.


Light tuning of the engine itself was always on the cards, since in the quest to lose weight I simply *have* to change the rear can, which weighs a ton on the standard bike. Changing the can *and* the full system would be best, since it'd allow me to switch the exhaust hanger and rear brake fluid reservoir to a separate plastic or carbon hanger, and remove both heavy alloy pillion peg brackets (they are *chunky* and removal will save a decent amount of weight).

I had an idea of cheaper engine work - just swap the twin for the 650 twin Kawasaki make (in the Versys, I think) - it's physically around the same size and IIRC conversions have already been done. But then I'm looking at not just more power than my maximum, but also much more torque. And the torque could cause problems with the swingarm, chain, etc. and especially the braking system - which only has a single disc at the front.

So potentially a re-bore, head work and some 'traditional' tuning on the existing engine was the original plan. I was happy with the idea of 32 bhp because I was expecting a pipe and filter to get me around 35, which would keep the top speed low but make the bike very nippy in the twisties…. but I wasn't counting on the 'published' 32 bhp being 25.6 bhp in reality!!!! Something more like 40 bhp would be the maximum, and would be the ultimate for a lightweight 250 built for cornering - any more than that and it'd be silly to continue when 600s are being made so lightweight these days.


The question is then - does anyone know whether the Ninja 250 engine is actually in mild tune, and whether getting 40% more power is a reasonable proposition with traditional tuning I can get any bike engine tuner to do (head work, cams, remap, exhaust, maybe a big-bore kit)? I looked at the numbers for modern 600 supersports - road bikes in Japanese-reliable trim appear to be making 100 bhp from 600cc these days, which is 166.67 bhp per litre. Scaled to a 250, that makes 41.67 bhp. Of course, modern 600 supersports are all 4 cylinder screamers, and the Ninja 250 is a twin. But Ducati make twins too… and they don't seem to be that short on power.


Anyway since the bike is great fun and I have no intention of *reducing* the fun level - just *increasing* it, without making it comfortable over 100 mph (it's not, certainly not at the moment), brakes and suspension are getting done first. Actually, I ought to do suspension first, because I'm finding that I don't really ever use the brake much - engine braking and sitting up into the airflow slows the bike enough for corners - I'm only using the brake in town and for emergencies! So suspension advice would be welcomed. I don't know enough to bolt on an Öhlins multi-adjustable shock and then set it up myself, I'd really need an expert to do this - is it feasible to work out the settings on a shock simply from bike weight, rider weight, engine power, riding style, etc. - or is it an iterative process with the rider needing to know how all the different functions of a shock (bump, rebound, etc.) work?

Tango13

5,539 posts

126 months

Friday 18th June 2010
quotequote all
Throw the standard suspension in the box marked "bin" and then get the forks revalved and fit a matching rear shock as the sticky tyres are probably to much for the standard setup.

I think I still have a PB road test of the ZZR250 which IIRC has pretty much the same engine so I'll post the BHP/Torque figures when i get home.

eta When Harris fitted all the Ohlins for me I asked them to set it for fast road use and it was perfect so don't worry if you know nothing of suspension.

Edited by Tango13 on Friday 18th June 11:51

bass gt3

8,683 posts

183 months

Friday 18th June 2010
quotequote all
Throw the whole bike in the bin and buy something more suitable. It really seems you are trying to make a silk purse from a sow's ear.
Whilst you may not want more power, if you have it, there's no law saying you have to use it. I really don't get what you're trying to do??
Oh, and until you put your's on a dyno, you don't know what you're starting with. So begin there if thats your chosen route, and the sky's the limit

Edited by bass gt3 on Friday 18th June 11:51

rhinochopig

17,932 posts

148 months

Friday 18th June 2010
quotequote all
It's a shame that the 250 four pots died a death, I used to love reading the specs of the baby ninja / blade engines. They used to rev to some amazing re lines - 18k IIRC.

cyberface

Original Poster:

12,214 posts

207 months

Friday 18th June 2010
quotequote all
Tango13 said:
Throw the standard suspension in the box marked "bin" and then get the forks revalved and fit a matching rear shock as the sticky tyres are probably to much for the standard setup.

I think I still have a PB road test of the ZZR250 which IIRC has pretty much the same engine so I'll post the BHP/Torque figures when i get home.
Yup, you're right about the suspension. The question is, what to buy? There's a big range of prices…. And I think that the ZZR250 was an IL4, though may be wrong.

bass gt3 said:
Throw the whole bike in the bin and buy something more suitable. It really seems you are trying to make a silk purse from a sow's ear.
Whilst you may not want more power, if you have it, there's no law saying you have to use it. I really don't get what you're trying to do??
I've already explained what I'm playing at… no need to follow the herd, is there? Anyway it's fun to do something different. Just because you disagree doesn't mean I shouldn't have a go. Your alternative effectively means buying a ZX6-R and either miraculously acquiring self-control from somewhere, or putting a rev-limiter on the engine halfway down the rev-range and only using half (or less than half) of the bike's performance. And getting the handling of a 600 when you want the handling of a lighter, slimmer bike. It's not the *only* solution, is it?

P924

1,272 posts

132 months

Friday 18th June 2010
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If you really aren't concerned about top speed, and want to increase acceleration, why not change the sprockets.

Steve Evil

9,925 posts

179 months

Friday 18th June 2010
quotequote all
The thing about the 250 Ninja is that it's a budget bike built with budget parts, unlike some of the older 250s being mentioned that were built to a much higher spec to begin with.

It's the same as trying to turn a 911 into a track day weapon, you could go ahead and start with a basic Carrera and have to install the roll-cage, uprated suspension, strip it out etc. Or you could just start with the GT3 RS and you've got a much better starting point.

Biker's Nemesis

36,189 posts

158 months

Friday 18th June 2010
quotequote all
Start with setting the sag, weather you have *standard or uprated suspension the say still needs to be set for your weight. Sag should be between 25 - 35 mm with you sitting on the bike with your usual riding gear on.

Brakes, Goodrich etc and some after market pads will be enough, if not then you'll be looking at a Brembo master cylinder and a wavey type disc. People fit the Radial master cylinder from a 636 to early ZX10's so that may be a cheaper alternative than a Brembo.



<*it's standard, not stock BTW>

God damn yanks.


Tango13

5,539 posts

126 months

Friday 18th June 2010
quotequote all
Suspension wise any of the big names Ohlins, Maxton, K-tech, your main problem is wether any one does stuff for your bike. Most 250 owners will ony keep the bike till they have an unrestricted licence so won't be interested in any upgrades. No demand so no supply.

The GPX250 was a twin which spawned the ZZR250 which is now the ZXR250. That engine has been around for about twenty years!

bass gt3

8,683 posts

183 months

Friday 18th June 2010
quotequote all
Steve Evil said:
The thing about the 250 Ninja is that it's a budget bike built with budget parts, unlike some of the older 250s being mentioned that were built to a much higher spec to begin with.
thats the point i was making. I'm not saying your goals aren't worthwhile, it's just that you might have started with the wrong platform. For a bike to have the spicier components, it usually follows that the bike exists in a certain performance bracket. And the baby ninja is a first bike, starter, entry level run around. Yes, you can fit all sorts, including carbon wheels. BST are up the road from me here in SA and they do them for the 250 RS, so no reason why not for yours. But you are now entering the murky world where you need to know if the chassis will handle the increased loads. Adding Ohlins front and back only for the chassis to bend like a twig won't help any. Remember, Kawasaki designed the bike for a specific purpose. You're now asking it to do something much different. The chassis will be designed for the expected loads due to the limitations of the constraining components, tyres, suspension, brakes, etc.
Really, i've been where you are. But you need to step back and really think about this. There's no wrongs or rights, just engineering realities. But at the end, it's your money, bike and decision.

Good luck

cyberface

Original Poster:

12,214 posts

207 months

Friday 18th June 2010
quotequote all
Chaps - I *know* that I may be on a fool's errand here. I *know* the bike is built with budget components to begin with, and I'd be far better off buying the bike that already came with the top-end components… but what bike may that be?

I'm guilty as charged of the 911 analogy - wanted a 993RS but couldn't afford one (prices went mental) so I bolted a supercharger to my standard 993 Carrera. Then uprated brake pads, lighter 18" wheels, Dunlop SSR tyres, etc. And yes, I was faster round Brands GP than the 993RS boys, for a while. But yeah, if it'd been possible I'd have got the real thing.

The trouble is that the UK market doesn't have demand for a 'Lotus Elise' type bike - they're all 'Ferrari 430' bikes. All of 'em. If someone can point me in the direction of a 250cc four-stroke sports bike that is built with top-end components and is designed as a low-top-speed ultra-lightweight corner-monster then please do!!! I'll go out and buy one.

I'm trying to make a modern, 4-stroke, reliable bike that is similar in concept to the Aprilia RS250. I don't want to buy a real Aprilia RS250 because of a few reasons - reliability, insurability, likelihood of theft and the highly strung nature of its two-stroke engine being most of them. I wouldn't be able to ride an RS250 to the station every day and expect to find it there when I got back, would I? They are also not made any more, meaning a second-hand bike, MOTs, etc. etc. I've looked pretty hard, but I can't find the 'modern version of the Aprilia RS250' on the market. Where is it?

As far as I can tell, there are no bikes on the market that do what I want. So, being fond of modifications and building specials, I've decided to have a go. There are a few riders on here who know *exactly* why I'm doing this, too. Nobody has to agree that I'm doing anything that makes sense, I just would like advice on the issues I'm likely to face, rather than the advice 'you're wasting your time'. Even if the bike never ends up fulfilling what I wanted, I'm not wasting my time, because I'm having fun in the process. OK?


BN - apologies - I've used both 'standard' and 'stock' in that first post… and I castigate those using Americanisms too, so must avoid the hypocrisy… By the way, standard front brake is a wavey disc, and I'm not suffering from lack of braking performance at the moment. And the standard rear shock isn't adjustable for anything except ride height, which is already correct...

Biker's Nemesis

36,189 posts

158 months

Friday 18th June 2010
quotequote all
Like anything, there's wavey disc's and there's wavey disc's.

Different caliper? if you go the twin disc route you'll be adding weight, extra caliper and disc.

Will an adjustable higher spec shock form another Kawasaki fit?

bass gt3

8,683 posts

183 months

Friday 18th June 2010
quotequote all
Cyberface,

Again, i understand your aims fo rthe bike, but realise that the aftermarket manufacturers look to volume. If the baby ninja is a stepping stone bike, there may never be the wealth of parts available. So suspension, engine etc may be a non starter. By comparison, you could have got yourself an older bike, not 250 that doesn't have fearsome performance, and gone silly on the mods. Think Monster, 750S, 900SS etc. Those bikes have great aftermarket support, especially due to the commonality of parts. So try not to get too hung up on the 250cc aspect, but think fun bike, good cornering, parts support and aftermarket.
Finally, as a point of reference, there's a new race championship started here, using hte kwak 250. it's seen as a stepping stone between the 150cc's and the 600's. And what are they allowed to change? Nothing, nada except tyres, pipe and the rear spring if required. Reason? No parts are actually available for the bikes in performance terms and changing nothing keeps the cost down and allows talent rather than wallet to prevail. And it's the only 250 out there. So if Kawasaki are the only entity in that market segment, what does that tell you? Like Suzuki being the only 750 supplier. Seems they sell enough to justify it's existance in the model line up, but not enough to make other marques come in as competitors. Sadly, you seem to want a bike that no one else does.

Steve

defblade

5,436 posts

163 months

Friday 18th June 2010
quotequote all
Are the power figures at the wheel or at the crank? Kwaka's 32bhp would be fairly healthy if it's 32 at the crank and 27 at the wheel. Not to mention "correction" factors. And consider the mag might have had an interest in making their OE figures "low" (worst run, least helpful correction factors) as then it's easier to make impressive "gains" in their article...

If you've got FI, try running on high octane petrol, for a start (*unless the hand book says it's some sort of massive no-no).

As someone's said, the only way you'll be able to tell what power your bike actually has, and if you've improved it later, is to get a base-line reading now (and use the same dyno for all further tests, too).

Sounds like you're taking the right course though - as with cars, suspension and braking fettling works much better in RealLife than outright power.

If you want to improve the power/weight ratio cheaply - eat less!! wink

Enjoy, and don't let the "I wouldn't start from there" comments put you off! Keep writing your essays smile

3doorPete

9,864 posts

184 months

Friday 18th June 2010
quotequote all
GPX250R, ZZR250 and 250 Ninja are all the same engine - 8v parallel twin. ZXR250 had the IL4. Each iteration has ended up with a slower engine due to emission regs. My GPX250R with a 2 into 1 full system and dynojet kit made 38bhp at rear wheel on a mid 90's dyno (probably about 34bhp these days). It also redlined at 14K rpm (1000rpm higher than 250 Ninja). It was 20kg lighter than a ZZR250 after the exhaust, weighing about 135kg and was almost a match for RG250's. It could also virtually keep with NC24 VFR400's etc from a performance point of view.

Having owned an Elise - they are not budget - just small and light without too much power and short on fripperies. All sports bikes have a similar concept to the Elise.

In my view the 250 Ninja is not an Elise of the bike world, more a 1.2 Ford Fiesta Zetec.

Honestly - a Supermoto would tick all of the boxes for light, low top speed etc etc. They can be made more comfortable with aftermarket seats and more practical with 18 litre tanks etc. A much better starting place for a project and ultimately a tonne more fun than a 250 twin will ever be due to their power delivery and bigger cc, but lighter engine (anything from 400 to 690cc singles). With a bit of crash protection they are virtually indestructable too. Don't even get me started on the wheelies either!

Each to their own, but if you are intent on the Ninja 250 tuning route, I'd stick with sticky rubber, aftermarket rear shock, revalved forks, racing pads and a full exhaust system with power commander. They do sound quite nice on a race pipe!

rhinochopig

17,932 posts

148 months

Friday 18th June 2010
quotequote all
Bikes that fit your requirements are:

Any of the 250 4 pots from the late 80s early 90s.
NC30
ZX400RR

Why the aversion to two strokes - a looked after RS will be reliable. Or you could even go for one of Honda's or Yamahas 250cc bike - both lovely bits of kit although now not cheap due to their desirability.

You mention insurance - massively modding a 250 will cost you the same as a standardish 250 2ST or 400 4ST.

The bike you really want is an RS fitted with that aussie 2 stroke 500cc V4 or V2 (I forget which now). Anyway it give you 100bhp and is the natural bike equivalent of the Elise. Or you could opt for one of the 250 450 crosser 4 stroke conversions.


cyberface

Original Poster:

12,214 posts

207 months

Friday 18th June 2010
quotequote all
I really didn't want this thread to get into an argument as to whether what the hell I'm trying to do with my bike is acceptable to the forum or not, FFS. If I want a bike nobody else does, that's a feature of everyone being an individual, after all. And modified, custom bikes are all over the place - not everyone wants to be, look, or act the same. Hasn't that *always* been part of the culture of motorcycling, anyway??

The initial question was regarding the engine. The base motor has been around a long time, it's old technology. However the article I linked at the start seemed to have got 40% more power out of it just by breathing work i.e. not swapping the motor, or boring it out for greater capacity, etc. I was asking if this was reasonable. Surely some of you chaps must know whether 26 bhp from a 250 twin is in 'high tune' or whether it's pretty low tune and I should be able to get much more from it… it safely revs to 13k already, so the internals are up to some high engine speeds.

After all, I've already got all the grip I need with the different tyres I've put on it, I'm not struggling with the brakes at the moment - they're just fine for road use (if I ever track it, that's when I'll find out about the brakes). Suspension is the other question, and yes, shocks from other Kawasakis will fit. A common mod in the USA is to swap for what they call the Ninja 500R rear shock, which is a direct fit… so presumably any 'aftermarket' shocks for the 500R (not sure what this bike is called in the UK - I think Kawasaki's name is the EX500) will also fit the Ninja 250. So I'm sure I'll find something there - the final issue will, of course, be as you mention whether the frame is stiff enough for all of this. I'll only find that out the hard way, though with the 250 racing series being popular, I'm not too worried about my modifications making the frame too flexible for the *road* - hell, I'm not a MotoGP rider…

As to just getting a bigger bike, I've been there. Heavier, more powerful, faster, 100+ mph everywhere when riding enthusiastically, etc. etc. I *know* you mean well with your comments, but I'm just trying to make a very lightweight performance bike that won't lose me my licence. That's all. I've tried the old grey-import 400s and they're too damn small (physical comfort-wise). The Aprilia RS250 would be perfect but for the reasons I list. Now there *used* to be demand for the type of bike I'm talking about - because Aprilia made one! With the 2-stroke no longer, that bike doesn't exist any more. And there's now a hole in the market.


Oh well, I'll shut up about it and stop the questions, and I'll post up changes as and when I do them… I really don't see how the bike could be so rigidly fixed to its standard output and performance - all vehicles seem to respond to some mild tuning, and I simply don't believe that the engine in my bike is maxed out right to the limits of its capability. The tyre swap showed a massive improvement in grip. The bike is already great fun to ride - I'm talking about a few upgrades here, not wholesale re-engineering like doubling the power, doubling the tyre size, swapping swingarms, etc. No different than a lot of you chaps do to your 600s or litre bikes, at the end of the day.

How much can it cost to take the cylinder head to a bike racing shop and ask them to improve it from standard, after all? As long as the increase in flow isn't outside the range of the EFI (at which point presumably a power commander / etc. could be used, no?) then surely it'll just make it better? These are budget built engines, so I'm assuming that like many cheaply made engines, the head casting will have flashing and other obstructions that are easily removed…

rhinochopig

17,932 posts

148 months

Friday 18th June 2010
quotequote all
Woah there - no one is arguing with you. Simply offering alternatives - this is a DISCUSSION forum, no?

If you look at 4stroke tech in that capacity, the best performing engines are fitted to MX bikes and they are probably putting out a standard max of 35bhp and that will be pretty stressed, requiring frequent maintenance. Taking your bike to those levels would require a lot of internal work I would guess, and cost you a fair bit to do so.

I know you don't want alternatives, but other than the commonality aspect, I well looked after Cagiva Mito would offer what you want - I'm 6' 5" and was stunned that even my gorilla frame fitted on one comfortably. They engine is 30bhp stock, and it is a very sweet handling little toy to boot.

3doorPete

9,864 posts

184 months

Friday 18th June 2010
quotequote all
I don't think you will have a problem with frame stiffness - definitely not on the road and definitely not with the tyres available on those rim sizes.

On the road, I used to set fire to my stock pads regularly before upgrading them and putting on braided lines. It only had a single disc (not sure about Ninja 250).

I think there won't be much to flashing etc on the ports as these days everything is made pretty well. I'm sure you'll get the best gains by dumping emmissions. Carbs are fully able to make as much power as fuel injection, but often small carbs are used as a way of retarding power. The GPX250R had 2 carbs, but revved to 14k as stock. Probably a cam reprofile might be good too, but not sure anyone has the knowledge on these.

bass gt3

8,683 posts

183 months

Friday 18th June 2010
quotequote all
regarding the head work, give Chris Steedman at CJS Racing a call. He works mainly with Ducati's, but a head is a head. His work is exemplary, and he'll provide accurate before and after flow data. With this, you'll get a good idea as to the possible gains.
Now to maximise the flow, you may need to change the cam(s) Are aftermarket cams available? If not, you might be stuck. Or will cams from another model fit? Improving an engines breathing is about more than flow numbers. Think duration, overlap, swirl, tumble etc
Next up, is there a power commander available for that model? if not, you might be able modify another approximate version to fit.(Versys)?? For example, i have a PC5 for the 848 on my 996 race bike. Did it fit? no, did i make it fit? Yes. Did it work? Hell yes!!
Suspension. The front might not be a problem with so many insert kits being available. The rear might be a challenge. Even a shock from another base model is never going to be great. But if it has the necessary functions, it might be able to be rebuilt and improved by someone such as K Tec.
Wheels. I'll guarantee the BST carbon wheels for the Ape RS250 would fit. Might need some engineering in regards to disc offsets, wheel spacers etc, but it can be done. And it would be a huge improvement.
So yes, it can all be done, and you know where such projects lead in monetary terms.