KX250 vs YZ250 Full Review


87 replies to this topic
  • UpAllNight

Posted May 11, 2009 - 01:04 PM

#1

As requested and promised. Here is my attempt at a decent review.

2006 YZ250 vs 2006 KX250

A little about me - I consider myself a high B level rider on average. I mostly ride tracks and will only judge these bikes by thier track performance. I'm 5.9' 163 pounds. I own both of these bikes.

Mods - The KX250 is bone stock. The YZ250 only has a pipe spacer, however I often ride without the spacer. This review will be without the spacer. So both motors are stock. Both bikes have stock suspension valving, however I did tune the suspension (through clickers, fork heights, sag, and oil level) on both to fit me and the track. (settings used are listed on the following post below). The jetting on each bike was change slightly to fit the weather. The KX needed the ignition pickup adjusted to cure the pinging (air gap adjustment).

Motor - The YZ250 is a snappy motor yet when used right seems to find traction well. The rear wheel never spins to far ahead of itself. It has very strong roll on from the bottom and thrusts into a meaty mid range then signs off slowly into its top end. Its not a rev motor but it doesnt mind reving into a overrev when needed, however its not the most effective way to use the power. The YZ doesnt mind a short shift. The YZ has a way to running very clean at any throttle, its snap has the same sharpness in almost all RPM's and is very predictable. The best words to describe the YZ's motor is Thrusty and snappy.
The KX250 is not as snappy. It has a smoother but longer feel to the power. It wont handle short shifting as well as the YZ, however it doesnt mind hanging out in its high RPM range for as long as you want it too. From the bottom it climbs instantly but smoothly, into the mid range it starts speeding up its roll and then at mid-top it yanks forward into its solid top-end pull.Once it locks into its solid top-end power it feels as if nothing can pull it down. You can stuff it into the most power robbing spots on the track and it wont show any signs of a struggle, even the sound of the motor will not change. The best word to describe the KX motor is smooth screamer. By the way, the KX motor pings to hell in stock form. Even with 40/60 race/pump mixture it will ping. I was able to cure it by adjusting the ignition pick up's air gap to 1mm (as suggested by dirt rider mag and others in the forums). This as well as some small jetting changes cured the pinging.

Sound - The YZ sounds zingier and crisper while on the bike but can sound almost boring if your off the track watching someone else ride it. The KX sounds louder, raspier, and has a higher pitch wail. The KX sounds great when your not the one riding it but isnt as crisp sounding as the YZ when your mounted on it. Both sound Great though.

Suspension - (setting used are listed on the following post below) The YZ250 has forks that seem to amaze. In corners they compress well. When braking hard and while the forks are compressed they seem to still be smooth and ready to smoothen out another bump with gentle ease even though they are already halfway through thier stroke. Bottom resistance is good, but they are very sensitive to fork fluid height being tuned correct. The YZ's shock is very good as well. Although the YZ's rear end doesnt feel quite as good as the KX's but pretty close.. The YZ's rear is pretty fluid and fairly transparent. Overall the YZ suspension is a work of art and the bike can be trusted going through the nastiest stuff. Out the box however the YZ needs a ton of tuning because It doesnt corner well and jumps front end high as well as too fast of rebound... its not raceable out the box, but once tuned its one of the best. The KX out the box is much better tuned and almost ready for the track. The KX250's forks are very good, although not as good as the YZ's. They handle chop well and have decent bottoming resistance. They never ride low in the stroke and always feel up to the task. Fork height adjustment in the clamps is important on the KX, it effects the corners as well as the straights. The KX's rear is simply amazing, even in the nastiest whooped out burm the KX's rear will just charge the bike forward leaving you in control to steer its direction. It feels like is has a ton of stroke yet never walloa's. Its not sensitive to clicker settings, its hard to upset its tune with the clickers but you gotta have the sag right or it wont handle right (will explain why in the handling section of this review). Overall the KX feels right, not needing much of anything.

Handling - The YZ250 is middle ground on everything. Even the bikes weight feels to be very centered. Its pretty stable in the straights and corners as well. In the corners it likes for you to sit way up front, stick your leg out front and weight the front wheel. Although inside lines is not its specialty, it will take them with ease if you corner it like I just mentioned and add some drag to the front brake thoughout the whole corner. The YZ is not a natural in the corners (raising the forks helps improve its feel though), but its predictable and consistant. Once you get to know the bike it will never surprise you in a bad way. Its more likely to want to stand up and over shoot the burn or rut than it is to drop you on the ground. It jumps well. Its not the most flickable in the air but can be whipped/scrubbed after you form to its stable stiff feel in the air. It likes any aerial maneuvers to be initiated early on the face. The YZ changes its pitch in the air through the throttle or rear brake with sharp ease, thanks to a crisp rear brake and snappy throttle response. The YZ is a great bike for beginners as well as fast guys. The KX250 is not very beginner friendly in the corners and favors aggressive riding to work right, but its rock solid stable in the straights. The wheel base is the same as the YZ (kinda long) but the head angle is as steep or steeper than a RM. This longer wheel base (along with its great rear end) makes the bike feel vary stable going straight, but the steep head angle makes the bikes steering very sensitive in the corners. if you give it the right signals it will reward you, but if you send the steering a ill signal it will drop you on the ground just that fast. In flat corners it rides a fine line between hauling booty and sliding out. If you can keep it in check the KX will out corner the YZ in flat corners, but if you screw up your done. The KX is very sensitive to the sag setting, if the rear is too high (low sag numbers) it will knife in the corner badly, too low (high numbers) and the rear will lose feel and hit the bumper too easy. The KX has very low feeling center of gravity. Because of this it is less likely to want to stand up in a corner if you bounce off an apex of a rut or burm, unlike the YZ which will stand right up if you dont plan ahead. The KX takes inside lines decently, its not as predictable as the YZ and the rev happy motor doesnt have the lower end thrust as the YZ, so your kinda stuck working the bike and clutch harder than the YZ. But where the YZ shoots out wide if you screw up, the KX'es sharper front end seems to allow you to correct a screw up without going wide. The KX jumps very well. Feels really flickable in the air and can whip/scrub with super ease. Its more likely to jump rear end high, which makes showboating easy. It lands just as soft and light as the YZ. In the air the throttle and rear brake doesnt seem to snap the pitch around as crisply as the YZ does, but its all good. The KX250 favors aggressive riding and likes a rider who knows what hes doing, at least in the corners.

Brakes - The KX has a better feeling front brake but worse feeling rear. But both are really top notch.

Controls - The YZ's controls are great. Good levers and good feel. The KX has a crummy feeling clutch lever than doesnt seem to favor using just one index finger and the shift lever seems too far inward. Your boot can sometimes get stuck in the YZ's shift lever area. Also the KX is harder to start in gear, but once started it has zero clutch drag.

Quality and fit n finish - Goes to Yamaha, thats no surprise. Aluminum frame, cant beat that with steal! Even though the Yamaha needed a ton of suspension and chassis tuning, out the box the motor needed nothing. Just start and go, and go, and go, untill you snap a piston or break a gear :excuseme:. The KX pinged like crazy, needed the ignition pickup adjusted and jetting to cure it (before you toast the motor), but at least the suspension wasnt far off out the box. The Yamaha has better hardware and better finishes thoughout the whole bike. The Kawa has some funky cable and wiring routings. Feel free to ask about the air gap fix.

There you have it, the YZ is the latest jap 2 stroke motocrosser thats a middle ground bike built to do it all for all and a serious weapon. The KX is a dedicated racer that is only happy if your charging hard, laying it low and throttling hard. Both are blazing fast and suspended well. Thier just different flavors.

  • UpAllNight

Posted May 11, 2009 - 01:05 PM

#2

Suspension settings - All clicker settings are referred to from the fully wound in (clockwise) position. So if its 10 clicks, thats 10 clicks out (counter clockwise) from the fully wound in position.



YZ250...

As listed in this thread http://www.thumperta...2&highlight=sag 3rd post down

Forks:
compression, 11 clicks out
rebound, 9 clicks out
Fork oil level (outter chamber), 340 ML (can very depending on your weight)
Forks slide up in the clamps to 8mm (which is 3mm higher than the index line on the forks, as seen in the picture on this link http://i17.photobuck....Picture229.jpg )


Shock:
Race Sag, 101.5 to 102mm
compression, 8
rebound, 4
High Speed compression, 5/16th of a turn out (from all the way in) which is basicly a hair more than a quarter turn out.


KX250...

Forks:
compression, 10 clicks out
rebound, 11 clicks out
Fork oil level (outter chamber), stock
Forks slide up in the clamps to 6mm measureing from the top of the fork tube (not the fork cap) to the top of the tripple clamp. Stock was at 6.5mm, however I found right on 6mm to be best for me.


Shock:
Race Sag, 99.5mm
compression, 9
rebound, 9
High Speed compression, 1-1/16 of a turn out (from all the way in)

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  • CaptDan

Posted May 11, 2009 - 03:25 PM

#3

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Gosh, tough job. Slave-ing away on a racetrack all day.

:smirk: :ride:

Great write-up, UpAll. Many thanks! :excuseme:

  • UpAllNight

Posted May 11, 2009 - 04:16 PM

#4

No problem. The write up was kinda lengthy but I was bored at work and had nothing else to do. I burnt 5 gallons in the KX250 this weekend, it was my first weekend on the KX250 but I think 5 G's of gas is enough to get the idea. The YZ I have had for years.

  • mks yz

Posted May 11, 2009 - 04:21 PM

#5

Yeah I don't know how you do it lol... Your review is an excellent review of the stock bikes, you should do reviews for the rags. However a couple ?'s

1.) How is parts pricing for each bike, and what has failed so far.
2.) Have you done much aftermarket wise to the bikes since then and what are the must haves for each bike.
3.) From your review I gather that for racing aggressive mx the KX is your choice and for play riding, longer races, or scrambles you would pick the YZ.

  • UpAllNight

Posted May 11, 2009 - 04:33 PM

#6

1.) How is parts pricing for each bike, and what has failed so far.
2.) Have you done much aftermarket wise to the bikes since then and what are the must haves for each bike.
3.) From your review I gather that for racing aggressive mx the KX is your choice and for play riding, longer races, or scrambles you would pick the YZ.



I haven had the KX long enough to break anything, however I have broken everything from fork springs to gearboxes on the YZ. Its not that the YZ is weak, I just put in alot of hours when possible. The YZ has a piston that is known the crack and shatter. I just replaced it with a wiseco. The YZ's gear box is also know to break parts from time to time if riden hard. The rest of the YZ is pretty much bullet proof.

As for aftermarket... Rcannon would know best. I dont know what he hasnt tried yet. For the YZ I would say a wiseco piston and maybe the pipe spacer on a stock pipe, at least thats what I'm using.

For racing... it depends. The KX would work best on faster tracks with sweeping corners or when your fresh and energetic. The YZ would work best on tighter tracks because of the strong bottom-mid. The YZ is also easier to ride when you get worn out and tired.

  • CaptDan

Posted May 11, 2009 - 04:42 PM

#7

...However a couple ?'s

Yeah, I was wondering about tires.

I hear the YZ's D739FA stock front tire works best on the drive to the track.

Could that color the review?

  • Helmet_Hair

Posted May 11, 2009 - 05:54 PM

#8

Good read! Pretty much confirms my suspicions on the KX....more of a hard charger, vs. the Yami being a little more flexible/neutral.:excuseme:

  • RCannon

Posted May 11, 2009 - 07:17 PM

#9

Thats a good report. I think its interesting to read how similar they really are.

I know you said the motors run differently, but with a few bucks spent in mods, one could basically become the other.

  • UpAllNight

Posted May 11, 2009 - 07:21 PM

#10

I know you said the motors run differently, but with a few bucks spent in mods, one could basically become the other.


That is for sure.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • RCannon

Posted May 11, 2009 - 07:24 PM

#11

I hope you continue to buy bikes..I like your writing style!

  • KX02

Posted May 11, 2009 - 07:38 PM

#12

Good job upallnight. I ride a KX and my partner rides a YZ. Alot of what you said makes sense.:excuseme:

Not sure if you find this to be true as well. My clutch is quite a bit stiffer than the YZ's although is does't bother me when I'm riding. My KX tranny shifts almost flawlessly, but my friend complains about missing shifts alot on the YZ, going from 2nd to 1st I believe.

  • OW38B

Posted May 11, 2009 - 09:22 PM

#13

Outstanding review of both bikes. Great job.

  • 2strokenut

Posted May 11, 2009 - 09:46 PM

#14

Thats one of the best reviews I've ever read on TT. Even better being that I have an 07 KX :excuseme:

I only have experience on the steel framed YZ's but a lot of what you said makes sense. It seems like the KX works better and better then more I push it. Awesome review!

  • Stu2

Posted May 12, 2009 - 12:56 AM

#15

I'm about the same level rider and have very different thoughts on the Kx. I bought it new in dec of 06 (it was an 07' model but identical to 06 except for decals). From new it turned badly, and was harsh and jittery. Even after I broke in the susp. It pushed something awefull, stood up in the corners, the back was a mistery, it was harsh, yet wallowed and felt numb.

I read an article in Mxa on this bike and thier review was less than complimentary, they said the susp was terrible and even after replacing the linkage arm to sort out the geometry it was bad. They said the engine was like an 80's two stroke, strong but not user friendly.

On the contrary in thier review of the 08' Yz 250 (almost identical to 06') they said it was the best 250 two stroke they had tested......ever. The shock they said was as close to works as you could get on a production bike and the forks were also some of the best.

  • UpAllNight

Posted May 12, 2009 - 03:29 AM

#16

I'm about the same level rider and have very different thoughts on the Kx. I bought it new in dec of 06 (it was an 07' model but identical to 06 except for decals). From new it turned badly, and was harsh and jittery. Even after I broke in the susp. It pushed something awefull, stood up in the corners, the back was a mistery, it was harsh, yet wallowed and felt numb.

I read an article in Mxa on this bike and thier review was less than complimentary, they said the susp was terrible and even after replacing the linkage arm to sort out the geometry it was bad. They said the engine was like an 80's two stroke, strong but not user friendly.

On the contrary in thier review of the 08' Yz 250 (almost identical to 06') they said it was the best 250 two stroke they had tested......ever. The shock they said was as close to works as you could get on a production bike and the forks were also some of the best.


Did they change anything on the suspension in 07?

I read all the reviews I could find for the 06 bike befere I actually rode it. You are right MXA dogged is, claiming it needed a PC linkage and pipe. All the other mags claimed it was great, it got a close 2nd is most other mags.

What I didnt get is most claimed they found 105mm sag to be best. 105 might make the front end more forgiving and less sharp in the corners but it really screwed up the feel of the rear.

  • deep diver

Posted May 12, 2009 - 05:17 AM

#17

So c'mon all nighta....Which is you're favourite??

  • KX02

Posted May 12, 2009 - 05:18 AM

#18

100mm sag and the forks set at 5mm works good everywhere for me. No headshake and great cornering, like you said the harder you push it in the corners the better.

  • Stu2

Posted May 12, 2009 - 05:23 AM

#19

I am not 100% sure if they changed it from 06, but I think the only change was decals. I remember looking up at all the articles on the 07' to make sure it was ok and read the Mxa article a week after I bought it and thought:banghead:

They changed the linkage to change the rising rate, I cant remember the details but they said it helped, but the bike was still 'flawed', On my second ride out I got the huckabuck leading into a berm and it spat me completely off, broke 5 ribs an my clavicle.......I remember that bike well

  • 35yz450F

Posted May 12, 2009 - 11:58 AM

#20

I am not 100% sure if they changed it from 06, but I think the only change was decals. I remember looking up at all the articles on the 07' to make sure it was ok and read the Mxa article a week after I bought it and thought:banghead:

They changed the linkage to change the rising rate, I cant remember the details but they said it helped, but the bike was still 'flawed', On my second ride out I got the huckabuck leading into a berm and it spat me completely off, broke 5 ribs an my clavicle.......I remember that bike well


Does 'huckabuck' mean something different in SA?





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