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2013 kx250f- thoughts on reialbilty of cammed and done motor

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hey guys!

picked up a 2013 about a month ago and am looking for more power over the winter

ive got a couple different ideas,

1. displacement

2. head work and cams

3. both

i really love the powerband of the new motor, coming off a two stroke i really am harder on

4 strokes, but this 250f loves to be reved.

my thoughts are that with jsut a big bore i will lose this in turn for more mid range

the second option, i feel i may lose some reliablity. like i said im a 2 stroke guy and have not

hopped up a 4 stroke before

3rd option seems like it would be a rocket but also a big price tag

also thoughts on hot cams, web cams, big vavled heads, tuning for all work being done would be appreciated. basically i want the best power to price ratio with reliablility in mind

thannks

dunner

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I have found that a big bore dual injector setup as is possible on the 12 and 13 KX250F is not very easy to dial in. I believe it could be done very well, but to just throw on a bigger cylinder kit and stage 2 cams is not going to do much other than move your power down lower in the RPM. The dual injector KXF250 bikes really love to rev, and a big bore kit kills that, unless you also get the crank stroked and the combustion chamber worked on, perhaps some porting and some major mapping work. The problem with the two injectors is that they are programmed to work together very specific to the stock displacement setup. Exhaust, cams, porting and so forth are very helpful, and I would go with those before I would do the big bore. You will not have a bad bike with the big bore and the right map, but you really need to be able to adjust the spray of the injectors individually to make it work up to its potential, and stroke the crank, all of which are not cheap mods. You would need a new ECU and have someone who can program that ECU with multi-thousand dollar software to work with the setup on a dyno to get it right. I had a 269cc kit in my 2012 KX250F, and I had a decent map for it too (it will not run without a map made for big bore), and it had some good midrange and low end power, but it lost the sweet high RPM power that the engine was designed for. I was happier once I went back to 250cc mode and ported the head than I was with the bog bore. Depends on your use and riding style too. I just felt like I was taking away the best thing about the motor by killing the high end power. You CAN make get the high end power back, but that is where stroking the crank and combustion chamber work comes in to play, which calls for custom engine mounts (or mod the stock ones) and a custom cylinder to fit the longer stroke. Lots of stuff to get the big bore working its best. I decided to keep the bike at 250cc and work with what is already the best motor in the class and build on its positives rather than trying to build a whole new motor, which is what you have to do for the big bore to work right.

So, if it were me (and it is...I got a 2013 a month ago too) I would get the head ported for overall power, get a nice exhaust system, copper seats and guides, del west valves, and maybe have crower power grind the cams for more lift if you want that, and get a new stock piston and new tires, dial in the suspension, and work on my riding technique. This bike has tons of potential, and it does not need to be hopped up to be super fast. I do have a couple of maps now for the 13 KXF250 and they make a nice difference in my opinion. I mapped the stock ECU and it is really cool because you can change each of the 3 maps that you access with couplers, so I have stock, a lean power map, and a rich power map for different weather conditions.

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Just curious, do you race? What soil/terrain do you mostly ride?

Unless you are at the top of A class, leave the motor and therefore reliability/durability alone.

If you ride mostly loose sand and are struggling with power, get a 450 or back to a 250 2st.

That bike has more than enough power for anything else.

Your bike has more nut than my 12 RMZ250. I have yet to need more even in deep cut loam going up hill next to 450s. Your bike straight rips stock!!

Just another suggestion for ya.

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i would say i am a faster b class rider on most tracks. i am very good in sand and can hang with most any one in the deep ruts and whoops. i really ride this bike to its potential. i love the suspension and could prolly spend the money and get it dialed! im just looking for that response, 450 like traction ride, i feel if it just had that bit more power all over i would be set, 4ht needs a little more pull up top and third could use a little down low, im not made of money and am just looking to get that bit extra to have a chance agaist a good rider on a 250 2t, i was that guy but it just tired me out too much.

drzadam, what would the mods you suggested run me? i am good with motors and can tear down my self, have the head done by a local engine builder, and could reassemble with new cams or ground stocks.

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i would say i am a faster b class rider on most tracks. i am very good in sand and can hang with most any one in the deep ruts and whoops. i really ride this bike to its potential. i love the suspension and could prolly spend the money and get it dialed! im just looking for that response, 450 like traction ride, i feel if it just had that bit more power all over i would be set, 4ht needs a little more pull up top and third could use a little down low, im not made of money and am just looking to get that bit extra to have a chance agaist a good rider on a 250 2t, i was that guy but it just tired me out too much.

drzadam, what would the mods you suggested run me? i am good with motors and can tear down my self, have the head done by a local engine builder, and could reassemble with new cams or ground stocks.

Why not just buy a 450? Not taking away from you and your skills, but a local B rider is not a national B rider. Watch Loretta video and see what a Loretta C rider can do in the 250 C stock class with a stock 250. Think about this, a 250 to mod right for power and longevity unless you have a money tree isn't cheap. you can have more than enough with a stock 450. I know of several 250 A&B national riders who practice on stock 450's to mimic modded 250 power without wearing those expensive motors out.

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I for one agree with the 450f's.. I don't like having to worry precision throttle attention. I love the 250fs because for the most part it's just pin it. I for one do not have the skills to get the full potential out of a stock bike but I also weigh in 195lbs [used to weigh 165 but holed up with a major back injury I gained weight] and needing some extra grunt would be nice..

With that being said.. You're looking for power way up on the top of the rpms and to get that you're going to be building a timebomb..

This is what I personally think you should do.. Practice a lot more and get used too using the bikes mid-upper range rather then the top of the rpms. Once you get more used to that you will start going faster and carrying more speed due to being a gear higher..

But you might want to consider a ISF of the trans. This will reduce friction on the trans allowing it to be more responsive and can gain you around a 1hp while actually increasing reliability. Get the ECU remapped. This will add some punch and wont affect reliability.

Once you get more attuned to riding a 4stroke by keeping it in the mid/mid upper rpms you then should be able to go with a big bore kit and get more punch and notice it rather then ride above its power.

As I said if you go with a done up motor at your current 2stroke riding mentality you're only going to end up blowing it up rather quickly and say "4strokes suck"

Good luck with what ever you choose to do.

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just curious.. how do you like the new kawi? im thinkin about rollin my RMZs for the new kawis. any cornering problems? pushing outta ruts or anything weird? high speed stability good down rough straights?

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as i just stated, the bigger bike tires me out too much, i used to ride an rm250

Some not all have had issues coming off 2 strokes. Learning to ride in a different power band isn't as easy as one would think with years under your belt of 2 stroke riding. Talking with my motor builder, head work, stage 1 cams and stock piston has been building great power down low through mid where you want it, plus keeping reliability.

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Fact: increasing peak cylinder pressure over stock will reduce durability (bottom end, transmission, etc.). It does not matter if it's from big bore, intake/exhaust, or adding extra fuel or ignition advance (mapping).

No offense, but if you are a fast B rider, you are definitely NOT riding this bike to its potential.

Leave it stock, maybe try +1 tooth on the rear to get the "response". You'll be shifting more but you might find a good balance point for you/track.

I would never exchange reliability/durability for extra power on a newer 250 4st unless I was a competitive A class rider.

Do let us know if you decide to go big and how it turns out. Thx.

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just curious.. how do you like the new kawi? im thinkin about rollin my RMZs for the new kawis. any cornering problems? pushing outta ruts or anything weird? high speed stability good down rough straights?

Same interest for the same reason. More focus on the cornering (I'm sure the motor and rough straights are boss on this bike).

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i was actually thinking of dropping a tooth in the rear. imgetting used to the 4 stroke style but i do have the mentality of a 2 stroke rider( finding different lines then the norm, being fast into corners instead of stop turn go, outside lines with speed etc.) i think i would benefit from just an exhaust and maybe a remap for higher octane fuel, along with suspension of course. maybe ill stick to that and see where im left, i do like the stock piston, headmods, and stage one cam idea

who do you recomened for headmods. also what kind of performance gains could i expect from a slip on, headmods(porting), race fuel and remap?

lastly, i love the bike, handles well, i have noticed that the front does like to push out of ruts. i did come off a 06 rm250 that handled unreal tho

i was actually thinking of dropping a tooth in the rear. imgetting used to the 4 stroke style but i do have the mentality of a 2 stroke rider( finding different lines then the norm, being fast into corners instead of stop turn go, outside lines with speed etc.) i think i would benefit from just an exhaust and maybe a remap for higher octane fuel, along with suspension of course. maybe ill stick to that and see where im left, i do like the stock piston, headmods, and stage one cam idea

who do you recomened for headmods. also what kind of performance gains could i expect from a slip on, headmods(porting), race fuel and remap? no cams

lastly, i love the bike, handles well, i have noticed that the front does like to push out of ruts. i did come off a 06 rm250 that handled unreal tho

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exhausts are a waste of a grand. just re map it youll get more out of that. i wouldnt replace the exhaust until you have to.. unless you have money to blow for cool looks. get your suspension done and it will handle the ruts a little better. for now you can slide the forks up into the clamps to let it turn a little tighter in the ruts.

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you asked a while back about the cost of head porting / valve job, exhaust, map, etc. A good plan that would not hurt your reliabiltiy would be port head and get copper seats and guides ($700 w/ Pro1RacingHeads) and get a stainless exhaust system ($450 - $500 for a yoshi RS-4), map is $50 - $100 depending on where you get it, an that would be enough to notice a major difference I believe. Leaving the cams stock will be fine...in fact you might think of trying a 11 or 12 intake cams because they retarded the cam timing 3 or 4 degrees on the 13 and that supposedly helps high RPM power, but it may not be ideal for mid power, so the same cam but advanced 3 deg I think is avail for about $150 from the kawasaki stock parts catalog... I wish I had saved mine because it would be interesting to try it out on the 13 and see the difference. Then do regular maint. and you should have a long-lasting bike. I like the idea of an ISF treatment for the tranny...these bikes don't shift as well as some already, and the reduction in drag is really worth almost a HP. I would love to do that, but the down time to tear the cases apart, send it in and wait, and then re-assemble will be more than a week for me if I am lucky. I can handle that, but I have been riding a few times a week right now so...

Anyway, it is easy to think about more power no matter what bike you have...the best thing you can do is practice with what you've got and make it work best for your riding style. A rear sprocket gearing change, with the idea of getting yourself to third gear as quickly as possible and staying there most of the track, can be worth some time savings per lap for sure.

Take it from a guy who has done every upgrade imaginable to these KXF bikes...the stock bikes are fast, and money will start flowing out like there is no tomorrow. In the end, the rider is the biggest part of the picture....what do they say, 10% bike/90% rider? Get your bike in great working order and ride it and become better. It is a boring answer, but nonetheless true.

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yes, i have decided to through a can on it, get suspension done, and get a remap. once the head needs some work i will then get it all done up!

thanks for the answers guys.

also i dont know how u guys would jump up a tooth in the back? i already use 4th and 5th alot. 4th almost right out of every corner. im no pro but i would like to think i hold my own

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only people i know who use 4th in any corner are local pros. must bog like crazy. and almost everyone here has said pipes especially slip ons are a waste of money. and unless you are on some gigantic tracks you shouldnt be using 5th.

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No way you are running 4th and 5th coming out of a corner. If you're looking for honest help or advice with your bike, you have to provide honest information.

What size sprocket are you currently running?

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how are you guys not banging 4th gear after corners? on tracks with even small straights i almost always make it to 5th, and no it is not bogging at all. i told you i was a faster b rider, but im lying right

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count your gears again on your next ride.. theres no way your using 4th out of corners unless its the first corner at glen helen, of if you are just destroying that clutch

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im pulling third to the top almost imediatly at the exit and shifting to 4th, i am not killing my clutch, i am not a new rider i simply wanted information on the reialbility of done up 4 strokes

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