More power ? KDX 200

My son has a 06 200 KDX. This is the second season and he is feeling he needs a bt more power..(surprise) We have been looking at pipes. the gnarly woods pipes take much off the top. Could use the torque but don't want to loose the top. Suggestions?....or 250?


Woods and torque ar ethe same and rev and desert are the same. It depends on the type of riding. If he revs alot then the rev pipe is a goot fit. If he lugs alot and pulls stumps then the torque pipe is better. It just depends.

My understanding is the PC pipes do not take as much off the opposite end as the FMF pipes do. Overall they seem like a better developed product.

Don't be misled by the just the cc's. The KX250 is alot more bike than the KDX not just a little. It is alot faster. Everywhere. And violent.

If your looking for power thoughout the band, then look at the Fatty by fmf, the Gnarly makes power down lower. I have the fatty on my 99 kx 250, and it pulls fairly strong from the begining to the upper end...

Ebeck...Violent..?? :applause:

Fatty was available for pre 95 KDX's. Post 95 KDX's you can go Desert or Woods that is is. One makes power down low one makes power up high.

Look into the PC Platnum pipes.

Yep the 250's jetted and piped properly are violent compared to play/trail bikes. Nothing like a 500, that is just absurd. Imagine a 1000cc thumper.

If you still want more power after you do the pipe, and jetting to go with it.

Check out RB Designs for head and carb mods, more power from the bottom to the top.

Hmmmm I dunno man. The divider plate mod actually blocks fuel spray. I have tested a spray pattern with a divider and the fuel spray actually hits the divider plate so air above the divider plate is fuel free. The fuel enters the intake tract at an angle. The divider plate interferes with fuel spray. Not the best mixture is achieved. Aside from that, I am usure on how if the slider is less than 1/2 open how adding a divider plate above the open portion of the slider acts like anything but a fuel spray blocker. At WOT it adds nothing that I see. I am sure people have all kinds of butt dyno testimonials on this mod though.

I may be missing something and this may be the best mod in the world but I just can not see it. It makes little sense to me but then again I am not the sharpest knife in the drawer. Chances are I am wrong on this but it is my opinon based on my own actual testing and observation. I can even post a video of the test. I was shocked when the fuel hit the divider and bounced down. Maybe I did something wrong. shrug.

Be advised changing the head is always a compromise despite marketing. I know a guy out here with a bored carb and modified head (I think just squish and quench) and piped and jetted and he gets alot of mid snap alright but it makes less down low than he did stock. There is no silver bullet in this.

The 36mm carb bore, you may feel it. I can not say but I have my doubts. I'd say why not use KX250 carb though? If you want big go big and add compresion. Why diddle with 1mm?

You can make more up top with all those mods true, but not every where. Cams or alot more displacment is needed for that.

If you have not opened the air box, added a pipe and jetted you will be pleasantly suprised though. I have seen an much as 10whp increase with those alone. On a dyno.

Just to give you an idea, a KDX with pipe and all jetted will make 30whp. Add a punched out carb and modifid head and you may get 35whp on good day with the wind to it's back down hill with an optimistic dyno. Heck, a KX125 with a pipe will make easy and thee motor is smaller. A KX250 can easily fetch 45+whp. The power under the curve willl be ALOT bigger as well.

An MX bike just plain makes more. The motor design is different. That said doing those KDX motor mods may make total sense for some and they may feel it worth it. Hey that is fine. Go for it! The modding process itself and testing is half the fun!

Once you get past the pipe and jet the effects are incrementally small. Big bore kit or new bike is how I see it.

I plan on borg my carb but not doing the divider plate. Not becasue the boring really adds something(it may, I am uncertian I would notice it anyhow) I am doing it just to do it.:applause:

You can always swap in a KX250 motor into the KDX frame the inverse of what I am doing, a KDX200 motor into a KX125 frame with KX250 suspension. You can find them on ebay all day.

Then again, no matter what you have you will always want more.

Good luck with your path!

Icarbon, I've ridden a KDX equipped with an FMF Gnarly and ISDE silencer, it had a ton of chug for a 2 stroke, and had a nice smooth build into the mid range. It seemed to have plenty up top to me, but I haven't ridden a stocker.

Cams or alot more displacment is needed for that.

Hmm...ya know, I went out and looked at the KDX sitting in my garage, and I'll be damned if I can't find a single cam on that whole stinkin bike. :eek:

And, I'd really like to know how you know how much difference all this stuff makes, when by your own admission, your only seat time on a KDX is test riding your neighbors.:applause:

For others, TrikeKid has a bit of a history dogging me on the CRF230 forum as well.

I know a Learjet is faster than a Ferrari but I have never driver either. Well, actually I have driven Ferraris but I won't go there, but you get the point.

KDX's are subject to the same laws of physics. 2 strokes are 2 strokes. I have been working on them and cars for over 20 years. I also have a brain and am an engineer.

Also most of the information is out here on this forum. I also spent time speaking with folks in the industry.

1) I can see the fuel hitting the divider plate. That is good how?

2) Just how much power do you think you get with a 1mm bigger carb or more compresion?

You see in the CRF230 forum that head mods in terms of percentage yeild 10% increase. Add a hi comp piston and a cam and you'll get 2-3 more.

Don't get me wrong that is good but if 25whp is not enough I doubt 28whp will be either is all I am saying. If people want power get a bike with POWER. I am just trying to set expectations. Head mods will not give you 10whp. They just won't. On a 2 stroke the pipe is everything.

A KDX willl aways make less than a KX125 which is a smaller motor no matter what you do to it. That is pretty well known.

Spent time at a dyno, actually close to 2 years. I saw alot of this stuff first hand. I also saw plots of LTZ450 quad hit 97whp which was really neat. I have actually seen the results of mods on the dynos. I personally looked at over 120 dyno pulls with different jetting and pipes on a KDX200 alone. How bout you?

There is a reason why a stroked race motor costs huge money. It is not enough to spend $100 on head work. A KDX with a 36mm carb, pipe, divider, jetting and what not will feel faster than a stock bike in some areas of the rpm range and slower or the same in other areas of the rpm range.

Those mods will make more power in other places other than peak power and that is noticable for sure. That is power below the curve. mPeak won't be changed alot though above what you get with a pipe. On a 2 stroke the pipe is eeverything.

The guy asked I responed. Take it or leave it. He can take it or leave it. He can also take the info and do his own research. I provided information that he did not have. It may be wrong. I trust he will act on it accordingly which may include laugh and ignore it.

One thing he won't do is throw thinly veiled attack like you did and always do to me. Please stop with those or I will leave this forum like I did the 230 forum.

Not wanting to start anything but don't knock the RB mods until you try them. I think others will also agree

The FMF Fatty had waaaaay more power than stock, but it was all midrange. If I had to do it over again, I would consider the Pro Circuit pipe.

I put the knarly pipe on our kdx200 it was basically a stock bike,it brought the bike alive.go with the knarly.if your riding a lot of woods and single ttrack stuff gear it down lower you will like it .hope that helps:thumbsup:

Thanks to all that replied. After listining to the replies here and other sites we have decided to go with the carb Mod and then one of the pipes.

will let everyone know how it all works out.


What are the riding conditions? For a 200, the KDX200 makes decent torque. Most people that want to go faster, not just want more power, seem to go with the FMF Gnarly Desert (rev = mid - top pipe).

Unless they changed, the Pro Circuit website currently just shows the Platinum 2 version for the 1995 and newer KDX's. FMF makes the Gnarly in a low-mid and mid-high version.

ebeck, you may want to ride a bike with the particular mods before commenting too much. I doubt the original poster's son will use more than the seat dyno, and pretty much all seat dyno reports on a pipe and/or RB Designs carb mod are the same (THEY LOVE IT!). Have you read the description of what all is involved in the modifications? I am doubting that you have ridden a bike with stock vs. RB modified, but I am also wondering if you have read what all is involved.

My KDX 200 has a Gnarley pipe, RB carb mod with 42/152 jetting, Deltaforce 3 reed valve, UNi air filter, no lid on the airbox, 12/50 gearing, KX 250 forks.

The pipe was a nice improvement but the RB carb mod coupled with the DF3 reed valve is what really woke this bike up! The RB mod with the DF3 is one of those easy bolt on mods that work very well together. I would never own a KDX with out those 2 mods. The performance difference is night and day.

With the stock gearing I have clocked it at 73 mph via the GPS.

My riding buddys all have CR 250s, KTM 200, KTM 450 EXC and for woods trail riding or just woods racing amongst ourselves the KDX pretty much stomps. It takes a long run of open road for any of the more powerful MX bikes to really make time against me. Actually the only bike that really is impressive is the KTM 450 that bike flat out rocks in wide open desert riding. Woods ride though it is reduced to looking at my rear tire.

The gnarly woods pipe adds a lot of hit down bottom from stock but does not take anything off the top. Not sure if it was said, but i didnt feel like reading all that lol. It is the best mod I have done to my bike.

I am doubting that you have ridden a bike with stock vs. RB modified, but I am also wondering if you have read what all is involved.

I said it may be great but does not make sense is all. Likley I am missing something. Again I may be missing something though. It may be great. I did state that it may affeect power under the curve and the is noticable. I was prtty clear on that.

People should be advised that thier bikes will not go from 30whp to 50whp with those mods is all I was saying. 32 maybe. Power under the curve may improve greatly annd that is noticable. I was pretty clear about that as well. I was merly speaking of peak power. I realize peak power is not everything but that is was I was speaking abut. I was pretty clear on that too.

People looking for power will likley not he happy with those mods for long is all I was getting too. Hey some may though. I am stilll boring my carb. Silll on a 2 stroke the pipe is everything. It is the single biggest prformance gain. If that is not near enough a new bike or motor may be in order is all.

Those mods may be very noticable in ares othr than peak power indeed but the effect is not to turn the KDX into a YZ450 is all.

I should have put opinion disclaimer on that post.

The mods may be noticable.

Did not mean to offend anyone.

Devils advocat is all.

My applogoies all.:applause:

G'Day all,

Great forum!!

I have been riding a KDX200 for a few years now and have simply fitted PC pips and opened up the air box, until recently.

After cooking it in the Tasmanian (Australia) Bush i found a damaged piston and cylinder. I then fitted a steel sleeve and the 2nd biggest oversize Wiseco kit available (1.5mm). During run in, I had major pinging issues which resulted in ruining my new piston and again damaging the cylinder in the process. (i was not happy) I then went for the next oversize again, 2mm oversize which is the biggest available from Wiseco. I had the head modified to blend in with the new cylinder size and lower compression just enough to stop detonation.

As the standard squish design is more suited to top end power this head work did help with bottom end power.

I also did mild porting to remove casting marks and a general tidy up.

The bike is now a pleasure to ride. I found that with the standard bore and the PC pipe lost way too much bottom end and was very hard to ride up steep slippery hills, which we have allot of. The power it made would have been good for fast grass track racing or motocross.

With the bigger bore and high compression it has much more bottom end and mid range and will chug up any hill if I need to. My clutch doesn’t get such a work out now. I would still go for a Woods pipe or something that develop torque much earlier. Although the power delivery is now fine for me, the bike is now my sons and the power delivery could still be a bit smoother for him, but he is getting to like it.

The single best modification I have made which has increased my speed out of site has been stiffer fork springs. No good having the power if it handles like a bag of wet rags.

NB obviously jetting must be spot on regardless of what you do and i have also had some success playing with the power valve.

I am not riding a YZ250F which suites my riding style, but even though the KDX200’s are a bit dated, I still think they are a great bush bike.

To quantify the effects of the now near-legendary RB mods on the KDX:

Remember feeling the effects of adding the pipe?

It happens all over again with the RB mods. And then some.

Wow that is a pretty incredible statment! Clearly there is something that is not obvious then. I will be sending mine out. Peace!

He has a description on his site. It is a good bit more than a bore and stick a divider in there. :-)

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