KDXRIDER.NET

1995 New-to-me used bike, new topend, cleaned KIPS, Cleaned Air filter, no lid, fresh br8es plug, new 607 reeds.

Jetting is too rich when at high RPM wide-open-throttle (WOT), and too lean when at low RPM WOT, I can jet for excellent topend but it bogs and looses power at WOT low RPM, or jet to have great low RPM WOT, and topend is blubbery. It idles beautifully and cruises real nice. Any ideas? Some over at TT say it is the nature of the stock pipe and a FMF woods will make everything wonderful. I would like to exhaust all other problems before trying this path, as I like the quiet beefy stock pipe.

Thanks

I appreciate the link to jetting 101, not saying I know everything by a longshot or I wouldn't be on here, i make my fair share of oversights and bumb things, but I need "advanced 2 stroke tuning 601" I consider myself a pretty good tuner, grinding slides and lathing needles is not new to me, but I am stumped on this one. The only circuit in play here is main jet, I am disregarding transients and focusing on steady-state wide open throttle.

Anybody else experienced this phenomenon with stock pipe?

Where is your jetting now? Most on here like 45, stock needle#2, and 155 main. I've found the bike makes considerably more power with the needle in #3, but I have the stock reeds in my bike. I personally didn't feel a big bang for the buck with FMF Gnarley pipe and would recommend a Pro Circuit, though the last time I tried one on a KDX, the Platinim II didn't exist yet. That being said, I like the stock pipe alot too.

You'll probably have to compromise somewhere.

Trying to get the system to carburate cleanly at WOT both low RPM and high RPM is not going to be easy.

On my hybrid with the RBD carb and a modified CR250 pipe I can be in third, chugging along at 11 mph, go WOT and it will pull cleanly to the moon. Tweaking the air screw for changes in temp is the way to get there.

I did not have many issues with the stock pipe and rejetted stock carb, as I recall. I also wasn't very picky back then. It probably ran like cr$p.

KarlP wrote:
I did not have many issues with the stock pipe and rejetted stock carb, as I recall. I also wasn't very picky back then. It probably ran like cr$p.

+1

Thanks everybody. I am at 5000 ft, been from a 142 to 155, runs great on top with 145, runs great on bottom with 155. I am using 38 pilot, but have tried a 45, 42, but too surgy at light cruise. Stock needle, 2nd clip, tried top clip, and 3rd. The only circuit at play here is main jet, using higher gears roll on and wait a second or two....disregarding transients.

" I personally didn't feel a big bang for the buck with FMF Gnarley pipe"
then something must be off somewhere. Even with stock jetting the improvement was huge, even more after jetting it properly.

I love to tinker anyway, so I am thinking of maching an additional circuit emulating one of those solenoid powerjet carbs that remove fuel on the topend by turnin on the solenoid above a certain rpm. I'll use a rpm switch to make it happen and use a tiny solenoid valve and plumb it like a dial-a-jet. But I want to make sure I ain't fightin a "duh" problem first.

Right off you need to get that stock needle outta there and put in a CEK or a BEK the stock needle is hard to tune. The CEK will g ive you a "power band" hit while the BEK will give you a smooth power delivery which is great for slippery conditions.

aren't these for rbd carb? i thought bel and cel were 4 the stock carb...

Actually, it's CEL or DEL for a stock H series. Definitely worth trying before you go machining something. The stock needle is less than ideal, certainly.

scheckaet wrote:" I personally didn't feel a big bang for the buck with FMF Gnarley pipe"
then something must be off somewhere. Even with stock jetting the improvement was huge, even more after jetting it properly.

Gotta agree here something was off here.
The FMF was the largest improvement of any engine mod I did to my kdf.

I here what yall are saying about the needle but wouldn't the needle be out of the equation when talking wide open throttle?

Will the fmf woods pipe even improve the very lowest rpm off idle torque over stock pipe, or do you give up just a little torque off idle in favor of upper low-mid-top power?

definitely YES on the low end. If you don't notice any improvement then something is waaay off...

Will the del needle give a honda scooter like cruise? On most bikes I wind up going two sizes leaner factory option needle, and grinding the slide up one size, dropping the pilot, raising the clip. I can't stand surgy, 4-strokin cruise. Yall think these needles will be a close starting point for me?

Oh yeah, I'm at 5000-8000 ft, rocky mountains!

Try the del. It will help clean things up. I probably have one I can sell you. My email is jbowens2401@yahoo.com

Sorry, didn't mean to hijack, but when I bought the bike a little over a month ago, it had the stock jetting, and a brand spanking new FMF "woods" and TCII on and that was the first ride.. With the stock jetting, I then put the stockers on and didn't really notice much of a power diffrerence, just a noise difference. I then put in a 45 pilot, dropped the needle to #2 and a 155 main and put the fmf pipes back on just to see if I might be high, and then next ride with same jetting, I put the stockers on only to realize last weekend that it was too lean so raised the needle one clip out on the trail and the bike made much more torque (it was around freezing). The biggest difference I noticed between the two pipes is that the fmf has the ting, ting, ting racier two stroke sound, but that was about it. I'm taking the head off the first week in Jan along with the carb to get RB'd and then I'll be able to get a better look of the condition of the top end. Maybe my KIPS is sticking or something.

to clarify: the muffler won't add anything (aside noise), the expansion chamber should make a difference.