Boring out the engine

[nlambert89]

Hello all,

I have a 2007, and I was wondering if anyone has ever done or seen a 250 with a bored out engine.

Any information will be greatly appreciated.

Thanks

[xXecuterXx2]

Welcome!!

And sorry, i don't. There is a lot of good info here, so I'm sure someone here will be along to help you.

[cuong-nutz]

A handful of folks here have but mostly on the new gen motors. The only member I can possibly think that has done it on the previous model is maybe RacerX. Lots of info in the newgen tech thread.

[Racer x]

Boring is straight forward. But there are no aftermarket pistons that I know of. The 2007 has a different shape combustion chamber so possibly the new gen low compression pistons MIGHT work . But I'm not even 50% sure.

[nlambert89]

Thanks everyone I guess more research is on my future. I will post back when or if I find anything out

[Racer x]

Let us know what you find. The first gen engine is going the way of the dodo so don't be afraid to experement. It's a fantastic engine. But old technology

[RickM]

An old race mechanic guy told me they used bore the 250 and put honda hurricane pistons in it, in the late 80's. I don't know if the guy was bullshitting though and I really think he might be lol.

edit: ok.. So after digging around some , it appears the Hurricane(1st gen honda CBR600) pistons are a direct fit in the ninja 250. it +1mm overbore for the ninja. That should give a nice bump in power.. especially if the head is ported match.

[BoBO]

If you call JE or whatever company, they can make a piston kit to your desired specs. I have done it on a few cars, I'm pretty sure they can make you one for your bike. I don't know about the down time though? I had to wait 3-4 weeks for my pistons.

[VaFish]

It's probably not done much because for the cost and work involved the pay off isn't that great.

Besides once you get the engine cranking out tons of horsepower, then you have to upgrade suspension, brakes, frame, ect......

If you want a lot more horsepower than a pregen provides, buy a used Ninja 500 or 600 and you will be much better off in the long run.

Of course if you are just one of the people that likes to do things because you can (nothing wrong with that), then go for it.

[Racer x]

The power of a bored out 250 is not in the peak power. I have gone out to 282 cc on a new gen engine. You get a little more top power. But the big increase is the midrange. That will make the bike more fun to ride. But if you want real power,suspension ,brakes even a ten year old 600 is better. My 06 zzr 600 rocked.

[zilog]

Originally Posted by VaFish

It's probably not done much because for the cost and work involved the pay off isn't that great.

Besides once you get the engine cranking out tons of horsepower, then you have to upgrade suspension, brakes, frame, ect......

The problem is that you will not get out tons of horsepower from the Ninja 250.
The distance between the two cylinders is relatively small, so you will not be able to bore it up a lot. I would guess that you can go up to ~280 cc at best.

Lets assume that you`ve bored the engine and had someone manufacture a set of pistons. You will also need new piston rings and new pins, because the pistons are larger.
You would also have to rebuild the engine (new gaskets, bearings, etc..), while it is disassembled, so you can make sure that it will run nice. Considering that you are in the USA - labor and parts for the whole process will cost a few hundred dollars.

Okay, so now you have 30cc more under your seat, but the bike runs worse. Why?

To benefit from the larger displacement, you will have to push more fuel in the cylinder. You will have to tune your carbs properly. Keihin CVs are good (I`ve seen cars running with them), so new needles or a jet kit should do the job.
Pushing more fuel in means that more exhaust gases will come out from the engine. I am not familiar with the Ninja`s exhaust system, but you may need a new one (mufflers and pipes) and/or engine head work.

You fixed your fluids flow, how much power do you get?

Less than 10 hp. Sure, you will get a better power distribution across the RPM range, but is it worth it?
In case you are going to race it in a certain class - go for it, but you will have to do a lot more to be competitive.
In case you are doing it to proof the concept or for fun - go for it, but there are a lot other projects that will yield more results @ the same cost.
If you are thinking that you will make the Ninja faster - yes you will, but the gain will be small, especially considering the expenses. It will be easier to find a larger bike. Even a 300/400 will perform better.

All the best,
zilog

[VaFish]

Originally Posted by zilog

The problem is that you will not get out tons of horsepower from the Ninja 250.

"Tons" is a relative term.

Ten horsepower, especially if it comes on lower in the power band, will be very noticeable on a pregen. If you are starting out with a well used and abused pregen it probably isn't making the power it had when it left the factory so we could be talking quite a bit more than 10 horsepower increase.

However, we are in violent agreement, the time and expense of boring out a 250 and the associated work to make the most of the greater displacement is probably not worth it.

You nailed the answer here:

Less than 10 hp. Sure, you will get a better power distribution across the RPM range, but is it worth it?
In case you are going to race it in a certain class - go for it, but you will have to do a lot more to be competitive.
In case you are doing it to proof the concept or for fun - go for it, but there are a lot other projects that will yield more results @ the same cost.
If you are thinking that you will make the Ninja faster - yes you will, but the gain will be small, especially considering the expenses. It will be easier to find a larger bike. Even a 300/400 will perform better.

To me boring out a 250 is like the guys that buy a 125cc Grom (or worse a scooter) then put a pipe on it and all sorts of other mods. Yeah ok you have the fastest Grom in town. That's like taking the best looking ugly chick to the prom.

[zilog]

Originally Posted by VaFish

"Tons" is a relative term.

Ten horsepower, especially if it comes on lower in the power band, will be very noticeable on a pregen.

You are correct, but (unfortunately) I can not guarantee how much performance will you gain. You may get only 2hp @ top. This will not make much of a difference. Most likely you will only feel the gain at middle RPM.

Originally Posted by VaFish

That's like taking the best looking ugly chick to the prom.

I laughed loud on that.

[Racer x]

I am not sure. But have never seen a pre gen over 30 hp. Anyone have any dyno runs that are that high?

[cuong-nutz]

Originally Posted by Racer x

I am not sure. But have never seen a pre gen over 30 hp. Anyone have any dyno runs that are that high?

ported head, 0.5mm overbore, balance, jet kit, etc:





~35 HP

He has a some good rebuilding info on his site which I have used in the past.
http://www.rcramer.com/bikes/ex250

[zilog]

Looks good!

I can bore my engine for little to no money, but than again - what pistons would you drop in for the +0.5mm oversize?

[cuong-nutz]

Kawasaki made .5mm over pistons. If youre going that route, I would just up the anty and go bigger. Go JE. I haven't had good luck with Wiseco quality. With the money on pistons, better off with a better platform and get a 300 motor.

But if you're stubborn and like to give it a go, get bigger pistons and port the heads. The heads are really restrictive. Also toss the counterbalancer. We have a a couple of great bios threads in the newgen area.

[Racer x]

I have mixed feeling about the balance shaft. It removes mass them the reciprocating parts of the engine . The good is the less mass will rev faster. But will less mass also slow down faster? Do you loose more RPM after you shift? Drag racing engine usually don't use light flywheels . Only road racing .

[agentbad]

Maybe cheaper to just do the 300r engine swap.

[cuong-nutz]

Originally Posted by Racer x

I have mixed feeling about the balance shaft. It removes mass them the reciprocating parts of the engine . The good is the less mass will rev faster. But will less mass also slow down faster? Do you loose more RPM after you shift? Drag racing engine usually don't use light flywheels . Only road racing .

I believe @mgentz and @spooh have personally done it so they could probably comment more. I'll test it out on the next engine I get my hands on.

[mgentz]

Originally Posted by cuong-nutz

I believe @mgentz and @spooh have personally done it so they could probably comment more. I'll test it out on the next engine I get my hands on.

I kept the balance shaft for durability. @spooph still kept his but made it inoperable. The reason for that is the oil gets passed through the shaft and by deleting it you lose oil flow. There was a lot of data on the best way to index and pin the shaft.

Yes it's costs a lot to get a little on the 250. But it's fun. Bragging rights are cool but funny. I love my bike but still want a 675r, 636, or r1m.

[zilog]

Originally Posted by cuong-nutz

Kawasaki made .5mm over pistons. If youre going that route, I would just up the anty and go bigger. Go JE. I haven't had good luck with Wiseco quality. With the money on pistons, better off with a better platform and get a 300 motor.

Did not know that, thank you!

It appears that the piston is Kawasaki part #13029 (13029-1201) and it really is 0.5mm overbore.

There is no point at getting the JE or Wiseco sets, considering their price. And I am not even calculating the shipping and taxes, if you are in Europe.

[Mohawk]

The EU ZZR250 puts out 30hp stock at the rear wheel !