No top end with FMF Gnarly

[JCW]

I took the stock pipe off of my 03 KDX200 and put an FMF Gnarly Woods pipe on. I can barely tell any difference down low and I've lost about 15 mph on top end. I could easily do 65 mph with the stock pipe and I can barely get to 50 mph with the Gnarly (per my Trail Tech speedometer). The bike runs great and I don't think I have any problems. Has anyone else noticed this? I think I'll go back to the stock pipe and try the V Force Delta reed cage and reeds. I hear they add low end power and maybe I can keep my top end speed as well with the stock pipe.

I wonder if the stock 03 pipe was improved over past models because I definately don't see that huge low end difference I've read about many times on this forum.

Thanks for your comments-

JCW

PS Canyncarvr, maybe the "Sticky Bros Traction Plus" additive I'm spraying on my back tire is causing too much traction and resistance?

 

[canyncarvr]

Yeah. Maybe your rear wheel is a 24 incher now?

I assume you are referring to a -35 pipe? The terms 'gnarly' and 'woods' don't say anything definitive about the pipe profile you have.

Bet'cha $10 your problem is jetting. The -35 runs way richer. Even if you were spot on before, you aren't now (having changed nothing).

Another assumption (nothing else happened)...the -35 will run one heckuva lot better than what your indicating. If you're still running 48/160 (stock) ..you're way out of whack!

I don't recall if you've said before. 'Runs fer crap' without a what's in there jet list won't help you much.....

Mississippi may be low enough to be close to stock jetting...but it's also dripping wet ain't it? There's a reason to lean it out.........water don't burn too well.

 

[JCW]

Thanks for the reply. That's certainly an option, but I've never fouled a plug and I never felt like the plug was loading up in slow terrain (like my KX250s used to do). It doesn't smoke that much either and it cranks 1st kick everytime. ??? It seems perfect, but I could definately be off somewhere.

A lot of guys I ride with run 3 oz to 1 gallon. I always run 4 oz. to a gallon. Everything else is stock. The pipe has no number on it. When it arrived, I called FMF and read the stock number off of the paper that was attached to the pipe to make sure it was an FMF Gnarly Woods pipe and they assured me it was. I'm fairly new to KDXs, so I can only compare mine to my previous 250 MX bikes (which is an awful comparison). One other thing though. I am still using the stock silencer, as I think (?) I recall hearing that the pipe made a lot of difference, but the silence (FMF Turbine Core) did not make much difference. Is that true? I was trying to keep the stock silence since it is quieter, but I could change.

Regarding sprockets, what do you suggest? I don't think I have enough low end to change and gear up for top end? Regarding jetting, I could move it one clip and see if it is too lean.

Thanks for you help
JCW

 

[splatt]

The gnarly woods pipe is meant for low to mid and falls flat at the top.

 

Steve

 

[wibby]

Have you done a WOT plug chop yet? That's the proper way to check how your jetting is. (at least for the main)

Sounds like you need read this: http://justkdx.dirtrider.net/
Click on Tech Tips; Engine; Carb Tuning

Read it, Learn it, Live it ;)

 

[Zerotact]

I remember being told that if my bike starts cold on the 1st kick it was definately too rich. I dropped my needle clip from the middle to the top (2 notches) I now have to kick it over a few times, but I could definately feel the power increase.

 

[CaptainObvious]

Yeah, I'd say rejet. Your 32:1 ratio is good, but if you are running stock jets, well that's bad. Don't go by the smoke, go by how it runs. From what you are saying the bike does't run well with the pipe. That shouldn't be.

Rejet and see how she goes.

 

[JCW]

Based on the KX250s I rode for years, I always based jetting on how the motor sounded and how it loaded up when riding slowly with minimal RPMs. I also checked the sparkplug to see what it looked like. I appreciate all of the comments and I will move it one clip and check it. However, never fouling plugs, never loading up at low RPMs in tight technical terrain, running smooth all day, and never seeing any oil at the end of the silencer sure (with my old school thinking) made me think it was fine. The bike seems to run fine to me, it just has no top end. It's like 6th gear was removed. I'll let you know after a little re-jetting. Also, looking back, I wish I would have gotten a Fatty pipe (in case anyone considering a pipe is listening)

Thanks again everyone-

JCW

 

[Dogman5]

The Gnarly pipe isnt designed to give you more top end. Its designed to give you significantly lower end power, but however sacrifice the top end..

Check FMFs nice charts and thier powerband charts on their website.

However, the loss is not that significant to where you should be loosing 15MPH on the top end. That is odd..

 

[ktmracer]

if you are coming off of 250 mx'ers you should have gotten the gnarly desert pipe. there is a big difference between the woods and desert pipes. the desert pipe hits much harder in the midrange and gives you nice overrev (relative to the stock/woods). although you will lose some of that 25 rpm no clutch roll on power.

 

[canyncarvr]

Confusion abounds most rampant....sheesh.........

Forget (for about the gadozenth time!!) all the 'desert', 'mountain', 'woods', 'gnarly' crap. It's a -30 or a -35. Period. End of story. The number will be stamped on one of the mounting flanges (not always the same one). It may well be on the inside of the flange.

The -35 (torque) indeed is not tuned for the upper rpm band...but it does not 'fall flat' on a 200. It will 'fall flat' on a 220...but then, a 220 'falls flat' all by itself in the upper ranges anyway.

The 'fatty' does not exist for the 'H' model kdxs. Well, unless they reintroduced it recently. The 'fatty' is a pipe profile that was touted to be an 'all-round' pipe...'better everywhere.'

If you believe that ad-hype....you're most welcome to it.

re: 'starts first kick every time'

Zero has it right. That's pretty straightforward.

Jetting is not an 'option'. Not if you want to get anywheres close to the response out of the kdx that it is capable of.

It is a requirement!

Changing oil/gas ratio does indeed affect air/fuel ratio...but the two are not same. Don't confuse rich/lean with 40:1 vs. 32:1.

BTW...40:1 IS 'richer' than 32:1.

 

[Canadian Dave]

JCW take a second to fine tune your jetting and I'm sure that you'll not only see improvements in your top end performance but everywhere else as well. Stock KDX jetting is very rich, unless you live in the Artic, and will certainly be detracting from your performance. Just to give you an idea how rich it is, most will drop from the stock 160 main to something in the 152 range.

David

 

[TVRider]

JCW,

You're getting great advice here. My 03 200 was a dog out of the box, I put a -35 pipe on it and tossed the airbox lid (I think that second part is significant) and it was a totally different bike!
I'm sure someone will correct me if I'm wrong but the improvement possible from the pipe is limited with the stock airbox config.

I have gobbs more low end and improved top end, just not as much improvement. I'm in swampeast missouri, not that far from you and I was running a 42 pilot, 152 main with the stock needle and clip position until I recently went with a new carb and the RB Designs' Carb Mod. According to my WOT plug chop at 80 degrees low humidity, this was still on the rich side. Hope this helps.

Tom

 

[DRECKFRESSER]

I just replaced the stocker with a k35 also and kept the stock silencer. (no airbox lid) Except for playing with the needle a bit, I didnt have to change any jet sizes. Plugs tan. I noticed a definite improvement in low-mid performance and hardly any loss in top end. Wich woods are you going 65mph through anyway?? :)

 

[canyncarvr]

From the woods behind me to the woods in front of me (leaving a pumpkin 200 in the dust btw) on an 'interconnecting' road.

But...that was more like 75mph (GPS certified).

Hey! Maybe it'll only happen once...but it did happen!! (the pumpkin part) ;)

 

[JCW]

Thanks again guys. I've been out of town for a couple of days and could not respond. I'm definately re-jetting now. At this point, the jetting is stock with the needle moved up one clip from the top, 2/3 of the air box cover cut out, and a -35 pipe installed. I think I'll probably start with a 152 main jet and the WOT check after another thorough review of the carb tuning section in Tech Tips.
Canyncarvr, thanks for keeping the pumpkin brigade in check. What an awesome forum.
JCW

 

[JCW]

Hey guys, I changed from a 160 main jet to a 152 which works best at the 2nd clip from the top and this bike now officially "rips" with a nice golden brown plug and no weak spots anywhere from idle to wide open.

I finally have enough power to change the gearing and get a little more top end now. I'm thinking of changing from a 13 tooth countersprocket to a 14 and leave the back at 47. Has anyone done this and if so, how much of a change was noticed (low end and top end).

Thanks again everyone. Now I can't wait for the weekend. I'm going pumpkin hunting.

JCW

 

[JCW]

I don't know what happened to my original comments from earlier today. I'll try it again. I switched from a 160 main jet down to a 152 set at the 2nd clip from the top and the bike rips now. Thanks everyone for the help.

Now I want to get a little more top end, since I have the power to change the gearing a little. I'm thinking of changing from a 13 to a 14 tooth countersprocket and leave the rear at 47. Has anyone done this and if so, how did it work.

Thanks,

JCW

 

[Racer#213]

i got a questions, when you toss the airbox lid, where do you put the electrical box that is bolted on top of it?

 

[JCW]

I cut out the back 1/2 and a lot of the front half of the lid, but left just enough for all of the edges to fit and for the electrical box to stay in place. I would guess that 75% of the lid is open. It seems to work well for me without re-routing the electrical box.

 

[KAY DEE EXER]

There is a threaded hole on the frames crossmember that it can be attatched to.

 

[CMcCarthy]

I gotta say, the K-35 and a re-jet transformed my 01 KDX. It felt like the horsepower doubled! Add to that the airbox mod and a RAD valve or equivalent and that thing will have you grinning ear-to-ear.

 

[JCW]

For the FMF -35 pipe and rejetting (152 main 2nd clip from the top), is the V Force Delta better than Boyesen? What's the difference in how they will preform. Is one better down low and the other better on top end, etc.?

Also, generally speaking, what effect will changing the reed cage and reeds have to do with jetting (typically make it leaner or richer, etc). I have enough power now to go up to a 14 tooth counter sprocket to get more top end and I plan to do that (if that makes any difference in the reed choice I need to make).

Thanks everybody for the help, I'm almost dialed in-

Thanks
JCW