250 carb change

[hybridkdx]

 Has anyone tried a 36mm carb on a 250?? Love my 03 250 for enduros, but with other bikes I have ran a smaller carb for more bottom end and less top. Has anyone tried it on a 250 yet?

[motopunk]

i had a 36 carb on 250 360 and 500 engines .. but for real much low end power you should also use a pipe designed for this kind of power delivery and turning the statorplate to a little bit later mark ...

[hybridkdx]

Already have the pipe, tried the flywheel weight, didn't like it lack of response off idle or low rpm. I have built several kdx's and the smaller 220 carb will add low end to a 200, and the larger 200 carb adds revs to the 220. Really wondering if anyone has actually tried it to a kx 250

[sandblaster]

Motopunk  wasn't talking about a flywheel weight.
He was talking about slightly retarding your timing.

[hybridkdx]

I realized that. I was hoping to beat the ones who are gonna jump on here and tell me to try a flywheel weight!!!! I put a 13oz on my son's 03 while I was still on my hybridkx. After buying my 03 and switching from my bike to his we both decided we didn't care for the weight. I have since cut 6oz off of it and will run it this weekend at the local toys for tots race. Have never retarded timing. Only advanced timing for outboard drag racing applications for a snappier motor. That will also be on my to do list.

[motopunk]

Motopunk  wasn't talking about a flywheel weight.
He was talking about slightly retarding your timing.

 ...  and i forgot the points of lowering compression or adding a reed-spacer... 

flywheel-weights give more torque, but doesnt change the engine performance as much as you try to find...  maybe it could help to add one, after all other mods are done,
for an similar effect like a flywheel-weight, you could also bring more rotating weight to the clutch by adding one steel-plate, before buying an expensive flywheel-weight, that maybe later only catching dust on your workbench .

some bikes, like ktm come in stock with alumininum plates in the clutch.. pretty light weight, but not durable enough.

what i tried to say is, that many performance changings could easy be done without buying expensive parts...like pipes weights and so on...   on some diferent mx-tracks i play a little bit with these effects. you only know the diferance if you experienced it... 

[hybridkdx]

I just put the flywheel weight back on, this time at 9 oz. As far as rotating mass, the Rekluse does that. Was hoping someone besides me was gonna be the guinea pig about the carb. But I know me and I will prolly end up doing it. I tried the spacer in the power valve, It definitely smooths out the hit, but adds alot to the mid range. It is removed for now.

[Motorrad]

dont forget exh spacers/washers.  can make the world of differance when your fine tuning.   I run 3 in my K5..

[motopunk]

i have a handmade 10mm reedspacer on my 83 kx 250. before this mod the bike performed like a 125 with the power of 250. very low at bottom, but mid to top like a rocket, which made it difficult to ride in small turns on hardpack or mud, because of the rocket effect the rear wheel was not controllable enough for me ... now i have a smoother power delivery. more bottom to mid, with the same top end. tried also a 38mm pwk carb instead of the 40mm mikuni but this doesnt worked on this bike for mx... 

[treedodgingfool]

You're looking for more bottom-end grunt without effecting response (flywheel weight drag) or increasing the mid-range hit (power-valve spacer/04 spring).  I know this sounds simple, but what expansion chamber/silencer combo are you using?  If you're still using the stock, a SST, Works or Fatty Expansion and you're looking for more bottom-end, I'd feel your best bet to accomplish that without the joy of refiguring out your jetting again on a smaller carb would be to reinstall the power-valve spacer/04 spring and get a FMF Gnarly pipe (the most bottom-end grunt of the bunch without over-empowering the mid-range).  From there, to increase bottom-end if you still find it lacking, a bump-up in compression, either using the Team Green specs from '03 to mill the head down (less compression = less power & slower response everywhere; no good unless you want a flat, unresponsive power delivery) or get a '04 head (already bumped).  Also, a longer then stock/shorty silencer, like a FMF "Q", will bump up back pressure which will give a slightly noticeable difference in low-end grunt and smoother delivery in combination with the other goodies.

[hybridkdx]

Currently running the fatty/turbine core combo. The valve spacer did really calm down the hit but added more overall power. Looking for not so much more grunt, but more of a kdx type delivery, with more than the kdx has overall. I rarely let the motor wind as my light weight causes traction loss. I also have a kx/kdx hybrid that I love if only it had more ooomph. Would love to have a kdx 250 type motor, but kawasaki decided to drop that engine instead of refine it's chassis.

[treedodgingfool]

Just give a little background on where all my test/tuning has been is with converting MX bikes to compete in east coast enduros with for the past 14 or so years.  I've converted/competed on '00 CR250, several '03 & '04 KX250s & a '07 KX250 (and now back on a franken-biked '03/04), besides riding tons of different enduro bikes, KDX's, etc over the years working in the motorcycle industry.

There's a couple of ways you can go about trying KDX'ify your '03 KX.  The resounding trait of a KDX motor in stockish trim is seamless power and loads of grunt (more then any 200 has a right to).  Best way to acheive that on a '03 250 is to fill in the gaps in the low-mid power delivery, lower the gearing and slap a heavy flywheel weight on it (or E-line lighting coil) to get that idle to nothing, tractable pull from the bottom of a hill kind-of-power.  Easiest way to acheive that is get an '04 engine and slap it in a '03 chassis (seriously, '03s have great forks for trail nasties and a linkage to match, but the linkage set-up does give it up to the '04 when the rocks turn to sand whoops).  The '04 engine was literally one of the best MX convert engines of all time that I've ridden/raced.  Smooth, tractable and a seamless, meaty power delivery from idle on up.  The next best thing, to do with a '03 engine for a KDXish power delivery without porting is as follows:

-Pre-Load Powervalve Spring w/ Spacer/ '04 PV spring
-FMF Gnarly Pipe (a must for grunt, I've run 5 different pipes on the '03, ths is best by far)
-Either a V-Force (2 or 3, but get used to replacing reeds) or Boyeson Pro-Series Reeds (must be for a '03) on Stk Cage
-The Turbine Core silencer is fine in length, just keep the packing fresh
-Flywheel weight, 11 ounce is a good choice (I've used none, 9oz, 11oz, 13oz & a E-line Lighting Coil, the coil making the most drastic difference.)  Yes, response will be slower, but that's what you're looking for when in need of enduro bike/KDX power/tractability (which the '03 engine lacks, thanks to the PV slamming open prior to the bike being ready to run on the pipe).
-Final Gearing, I've used 13/51 & 13/52, 13/52 is perfect in my book, I like to have the power on tap and we don't have much for high-speed stuff.

I've tried plenty of other mods (different black box, Power Now, etc), but what I listed here I felt were the best spent money besides keeping the engine fresh.

[hybridkdx]

Can the stator still be bought? Would love to have lights. I remember a man looking about a year ago and said they were discontinued. Would love to port the motor, but the real need would be lowering the ports, which is kinda hard to do. I have never ported a motor for less top end, only for drag racing. Prolly wouldn't hurt to learn to ride better as well

[treedodgingfool]

E-line stopped the lighting coils long ago (unless you can find somebody willing to part with one, but KX ones are rare, wish I bought more then one now).  You can run a Powerjet lighting set-up, which with todays new LED Cree MR16 bulbs throw some serious light with minimal watts (PJ good for 14w on '03/04).  You could run on a Powerjet '03/04 a MR16 Cree 9w (50w eqv.) which is more then enough to do a little night riding on.  As for porting, I'd only send it out to somebody reputable to get it right.  The mods I listed as the sum of their parts would really get the bike close to what I think you're looking for (an enduro convert).  It'll be a lot easier ride, for sure!

[hybridkdx]

Why doesn't Kawasaki make a purpose off road bike like the 125/200 or 250 chassis 250 kdx motor? Fools could really take alot away from KTM. And it would be very cost effective to build. If service honda can sell em at 12,000 I am sure Kawai could at 7,000