Help me tame the beast

[BucKat]

I've been attempting to jet my bike with great success.
However, the power band hits way too hard now. Makes trail ridding real tricky demanding 110% concentration to avoid getting tossed into the rubarb. I've read the jetting guide and "EMERGENCY RB Designs Jetting Info Needed" ( yes all of it).
What I'm looking for is strong linear power all the way though the throttle range with a gentler hit. Currently it is too mx like.
It pulls hard past half throttle then runs a bit flat 3/4 to WOT. 160 main on order.

10'C
49% humidy
elevation unknown but consistant ( toronto canada)
FMF pipe and silencer
boysen reeds in stock cage
158 main
48 pilot
A/S 1 1/2 turns
R1173N needle 3rd clip from top
#6 slide
float set to 16mm
Air box lid removed
BR7ES plug
KIPS clean and fully operational
50:1 mixture
13 48 sprockets

The EMERGENCY RB Designs Jetting Info Needed recommends a CGK needle for my year bike. I don't know what type of response this will give me..
Perhaps retarding the timming or installing a few exhaust gaskets????
thanks
Joe

 

[bscottr]

Originally posted by BucKat
Perhaps retarding the timming or installing a few exhaust gaskets????

Joe,
I retarded the timing 1-2 degrees on my KX and it made a big difference. I also have a 9 oz. FWW.

Good Luck,
Scott

 

[OLD-N-SLOW]

Buc,
Try a b-- series needle such as a bel,bek. You did not say what pipe you have, kg-30 or kg35. The 30 is the rev pipe, 35 is the torque. The "b" series
has a much smoother delivery. I think the 1173n is an A series needle and not real good on the kdx with the 35 or 36 carb.
I like the hard hit of the c series needle so I,m not the best to comment.
Try to get fishhead or canyncarvr to respond.
As far as timing goes less=less power.While its probable it would soften the hit
and maybe extend the rpms(a little) why do all mods you have just to get rid of the power you paid big bucs to get? Play with the needles and get the power AND the delivery you want.
Steve

 

[BucKat]

I bought the bike with all the mods mentioned. Only thing I have done really( to the engine anyway) is clean the KIPS and jet. I'm not sure what the pipe is beyond a FMF gold series. Is it stamped somewhere?
When I got the bike it was flat through-out the entire throttle range.Now it really snorts down low but hits too hard.Don't get me wrong, it fun on the wide trails but tough on the tighties. If I can figure out how to make the transistion more tamable I will then have the means of tuning the bike for any given days ride.

Once I get the jetting spot on I will focus my attention to the timing and or gaskets in the exhaust.

Will the bel or bek work well on my year. Most of the needle mods I've read so far where for '95 and up...I'm not sure how to choose needle for my application.... :think:
I willing to put the time into it. I know it will run better so the quest continues.

thanks
Joe

 

[OLD-N-SLOW]

Buc.
i thought it was a 95 and newer...sorry. However if it is a 35-36mm pwk
you should be good to go. After looking some more I would try a cek first
and jet from there. You are using a bgp now. cek will have a shorter and smaller dia. straight area. Also more taper. If your current jetting is right
this needle may make you a little rich but you can work on that.
I think you will be impressed with the change.
Steve

 

[jeffw]

I'm not sure what the pipe is beyond a FMF gold series. Is it stamped somewhere?

I bought my KG-35 pipe from Fredette used and never was able to find the model number stamped anywhere. Some here have said its stamped right at the exhaust header, not mine. You can easily tell the difference visually, however. The rev pipe has a header section that hangs low and parallel to the ground before turning up and opening to a large bell high on the bike. It has a classic MX pipe look to it.

The 35 pipe's header section is higher and angles up to a much smaller bell. The 35 will miss your kickstart lever by a couple inches, while I've read here that the 30 somtimes hits the lever.

I bet you've got the FMF KG-30 Rev pipe. I rode a KDX with one of these and what you say is true, they hit hard, and its by design. The KG-35 power delivery is linear with no surprises. The power starts so low you'd think you were on a four stroke, its a perfect woods pipe.

 

[canyncarvr]

The '11' in an 1173 needle is the taper angle. It is a 'B' series taper (1º15"). Guess you know that part now.

I don't know what works or what doesn't in an earlier model kdx. Generally speaking, though, a 'hard hit' is often the 'recovery' of the engine after a poorly tuned spot.

Look for some corroboration on this, but I'm curious about such a long needle (39.95) and such a large diameter (2.735) coupled with a #6TV, topped off with a 48 pilot? Seems a mismatch to me.

Earlier kdxs could run a 'fatty' pipe. I think it said 'gold' on it. FmF says this is supposed to be an 'all round' pipe. I don't know what model# they gave that pipe, but it should be stamped on one of the mounting flanges.

I'd expect more of a problem with a bike that was flat on the bottom then hit hard about midrange. If yours is strong on the bottom, then flattens out up top, where's the 'hit' part?

 

[jeffw]

cc,
You must have been writing your reply when I was editing mine. I don't know that I checked the mounting flanges for the model number, I'll do that when I get home.

My pipe has "FMF Gold Series So. Calf." and "Feel the Power" stamped on the bell. It bolted on with just the usual gentle persuasion others have had to use with their new pipes so I'm assuming it is for a post 95 bike and that it is a KG-35 based on its small distinctive shape.

 

[BucKat]

yeppers she's a pre '95.
BGP is correct.

The only stamp on the pipe besides "FMF Gold Series So. Calf." and "Feel the Power" stamped on the bell is N-14 KDX 060594.

My main is still a tad lean causing the flat top end. Weather will warm up soon so I'd expect the 158 will do the trick in a couple weeks. I'll still try the 160 for now.

The hard hit I refere to is something like this.
1st and 2nd gear are too responsive for the woods so I use 3rd. This produces a really strong 4-stroke like pull. Low revs but will still hooks up and lift the front wheel off the ground when requested.(this I like). As the revs pick up and the pipe comes on the throttle response is so snappy it's tricky to ride. ( my lack of experience falls into play here).That's the hit I refere to.This pipie power is great in the open trails,dunes and track but for me ,,,not in the woods. Perhaps I should just ride my son's xr100. ;)

As I read through the "EMERGENCY RB Designs Jetting Info Needed" thread I thought I had stumpled across a means of gaining a smoother more predicable power via jetting and playing around with different needles. Maybe I read too much into it but I still want to learn as much as I can about this most favorite bike.

Steve,, are you saying that a longer tapper will produce smoother power through mid throttle .I'm I correct on that.
I've read the needle jet guide on JustKDX. It's alot to stomach for a newbie.pheww!!

CC
The #6 TV is stock on the 90. The orginal 1172 needle was scord so I bought a 1173 as advised on the jetting guide JustKDX. 48 pilot is stock as-well. As far as I can tell the 48 with the A/S at 1 1/2 turns seems to work nice.( again my lack of experience play a large roll here).
It'd be nice to have someone in the know take my scoot out for a test pilot and tell me where it needs work.
Thanks for all the replies.
Joe

 

[BucKat]

When I bought the bike early last year it was running lean all through and the reed cage was in upside down. This results in a 25% blockage (approx.)
Perhaps now as I get the bike running better and realize the power it should have I'll just have to take my time and learn how to ride/control it...
Hmm doesn't sound like a bad thing to me..
Anyway,,,,all hep is appreciated.
Joe

 

[MARC]

the bike sounds like way too much fun to me, I'd leave it alone if it were mine and the the jetting looked good!!!!!!!!

 

[jeffw]

Sorry, I thought we were talking about a post 95 bike. I did find K-35WDS 050396 stamped on the inside top mounting flange of my pipe. I guess a "torque" pipe wasn't available for pre 95 bikes?

It may not be possible to completely jet away a mid range hit and still have the bike make max top end power, its a trade off. If you look at dyno charts you can see a hit as a section of the curve that increases at an increasing rate. You don't want this, even in an MX bike, unless you're trying to produce a very high power linear stretch above the hit.

You sometimes here the phrase "keeping the bike on the pipe" when referring to riding a 125. Good 125 riders never ride through the hit, they keep the RPMs above that spot up in the linear part of the cuvre. It may be fun to ride through the hit, but its hard to control the bike in a technical spot at the same time, be it woods or an MX track.

In the woods you want a near linear curve, or better, one that increases at a decreasing rate, like most four stroke power curves.

 

[BucKat]

I'm not looking for top end power..More so looking for great bottom end with a milder mid range hit.Of course I'll get the jetting correct all the way through and have to live with the top end..( no biggie)
I ride under 1/2 throttle mainly. Very rarely do I ever open it up.I ride with my 12yr old so I do alot of waiting.Besides that, I love the technical tight trails.
I was hoping to find a new needle that would smooth'n out the mid range hit.

CC
You mentioned that the #6 slide with a 48 pilot and a 1173 needle was an unusual combo,,,,
What would your recomendations be????

jeffw.
I'm still not sure what pipe I have...
The linear curve is spot on to what I'm looking for.If I can tune the bike to have that curve or type of power and ,,,,,knowing how the bike runs now( mx like) I can tune the bike for either on any give day...( that'd be the ultimate)
Joe

 

[jeffw]

You have a pre 95 pipe. When people here talk about the FMF 30 and 35 pipe they are talking 95 and later. The chance of one of these new pipes bolting up on your 90 are slim to none. Maybe someone has "made one fit" but I haven't read about it here.

A company called DG still makes an "enduro pipe" for your bike. Check this out:
http://www.motorcycle-superstore.com/product.asp?Dept=33&ID=4450
Back in "the day" DG was "the" aftermarket pipe to have. I bet this pipe will give you low end, no surprise power you're looking for.

 

[G. Gearloose]

BuckKat,
Your 1st and Second gear should be more usable than you describe. I run the same needle on my '91, but run a 45 with the AS at 5/8 to 3/4, and it pulls like a tractor off-idle, If I ran the AS at 1.5 like you desribe, its flat off idle then lurches, and breaks traction, encouraging me to short-shift when it was tight going. But I'm not certain what the #6 slide throws into the mix.

 

[jeffw]

Yikes! Check this out:
http://www.fmfracing.com/01/dynocharts/02 KX250 DYNO.jpg

This KX250 FMF pipe makes the hit at 6K much worse (or better, if that's what your'e into!) than the stock pipe and they're actually bragging about it! Would you ride this bike in the woods? This would only be an advantage for the most expert MX rider, imo.

 

[BucKat]

Thanks Gearloose.
I'll give the 45 pilot a go.Mine too pulls hard off idle but gets real snappy when the pipe turns on.If my chin isn't over the cross bar when the pipe hits it can really toss ya around.The pipe seems to come on regardless of throttle position. Even if held constant at 1/8 throttle the pipe hits when revs climb to a certian point.

I do use 2nd in the woods but only when going real,real slow around tight trees or up large rooty steeps.
I'm starting to believe my pipe is the cause. Maybe hoping jetting will ease the pipie hit.

From what I've read, the slide is manily in play at 1/2 throttlish so I too don't know what to make of it..( lots to learn no?? ;) )

My mistake...my pipe is stamped K-14 KDX 060594 Not N-14 ( whateven that means) I'll do a search for that.


Yikes,,that 250 must burn over 6000rpm.





I WILL FIGURE THIS OUT! ;)

Thanks mates.
Joe

 

[Canadian Dave]

Hi Joe and welcome the JustKDX,

FMF only makes one pipe for the 1989 to 1994 KDX200s. Its a moto pipe that improves all round performance from top to bottom and isn't as focused on one area of the power band like a rev or torque pipe might be.

Did you get any of the stock parts with the bike? If you have a stock pipe you might consider installing it when you head for the trees and the FMF pipe when you’re riding in more wide open areas. You could experiment with the stock silencer as well.

Adjusting the timing is a good idea and is worth playing with. www.eric-gorr.com has some guidelines for adjusting timing to point you in the right direction.

You might consider trying either a 12/47 or 13/50 gearing combination. Going with a 13/50 will require that you get a longer chain ( 110 links). This will allow you to better utilize third gear and you’ll likely be able to lug the engine in third rather than shifting down into second and running at a higher rpm. The hope is that you’ll be able to avoid the abrupt power as the engine comes onto the pipe by lugging the engine more/longer in third gear.

You’ll likely be able to smooth things out a little with jetting as well. You might consider trying something in the BGL range. Hopefully going with a smaller straight section diameter (richer) and a leaner pilot to accommodate will smoothen thing out. The idea is to add more fuel at lower throttle setting so that when you wick the throttle open there will be more fuel available in the crank case (bellow the piston) to allow for a torquey linear response rather than a crisp sudden response. You have to shift things to a rich side at lower throttle setting without getting so rich that you are loading things up and fouling the plug. Typically a C taper needle will make the hit more pronounced.

Out of balance jetting will make a hit more pronounced. For example too much fuel at lower throttle setting with too lean a transition onto the taper can cause the engine to sputter than hit too hard as things suddenly lean out.

David

 

[BucKat]

HI CD. Thanks for the welcome.

I've been with Just KDX for over a year now.( just under another name,,,,lost my password as Bucket)
I've been reading alot about the Kdx under this form and enjoy it much.

I unfortunetly don't have any stock parts.(pipe/silencer etc.) :( . I'll have to live with what I have for now..I belive in making what I have work first, then expand from there.I'm going to send an e-mail to FMF for more detail on my pipe. It fits like a charm so I believe it's authenticly designed for my year(not a pipe that was forced to fit)

Read Eric's guide on timing and I do keep a log on my jetting progress.I'm looking forwark to retarding the timming but only after I get the jetting correct..One thing at a time right! ;)
I'd also like to tamper with installing several exhaust gaskets to try lengthening the straight section of the pipe resulting in more bottom end.

I do have an extra 12 front and I'll give that a go soon.If I like the results I'll go larger on the back next chain change out.Currently third gear is my gear of choice in the woods..Low rev's,,,tones of torque.

I am learning a lot about jetting and general tuning as I read and experiment with my bike..From what I had, when I first bought the bike, to now is a huge imporvement but there is still lots more to go.

The bike pulls like a tractor down low now but I''m sure it can only get better as I try new/different things.I do like the way it turns on but,,,,like I mentioned it can be tricky. I will try differnt needles as recommended..
If I understand corrently a B taper is more so what I'm looking for as compared to the C I have now. With my set up now I don't get any fowling or sputtering down low. It pulls nice but turns on too hard.( for me anyway)

Excellent to hear from all. Thanks and keep the advice comming..

One can never know enough... :) Learn form experience,,,even if not from your own........

Joe

 

[fishhead]

as far as needle selection goes I would try a bel-3 or 2 to start and a cgl-4 to start with a 158/160 main and a 48 pilot. I also would check the kips valve. Those bikes are generally pretty smooth so it might be a good idea to double check the usual things. a cgk-4 will give good throttle response and richen up the jetting above 1/2 throttle. The pre 95 bike seem to prefer richer jetting on the main and pilot than the 95 on bikes and the jet nozzle is slightly lower so you will use a longer needle than pre 95 bikes.

 

[BucKat]

Thanks for the reply Fishhead. :)
I'll give sudco a call and order several needles. Guess I'll grab a 45 pilot for the hot weather as well. ( just in case, I don't want to be waiting for jets if I want to get this puppy straight).
Pooie for me,,,I just threw my knee out :( ( none dirt bike related -thank crap- ) so riding will be off limits for awhile. Guess this will be a good time to take the top end apart and do some extra work..Rings and such. Kips have just been overhauled so no worries there.Guess I may as well build that jig to get the dents out of my pipe as well...I'm also working on a pvc bike stand for us none welder types..( I'll keep that posted as progess continues)


Please keep the recommendations comming.....If I can't ride,,,darn-it,,,I'll read.


Thanks all
Joe

 

[BucKat]

Took top end apart and whaalaaa,,,found one striped KIPS valve and one broken in two places..
Can't believe it as I just replaced them at the end of last year..bugga.


Now I need to find out why the keep stripping/breaking.....replace with new ones,,,,,, then continue my jetting quest.

New jet needles on order from sudco. Could only get the cel for now as the others are on backorder.


Joe

 

[BucKat]

Will continue jetting quest once other problem are rectified..
see "KIPS valve keep sticking" thread for more details..


pheww! will it ever end...I hope not. :)

Joe

 

[BucKat]

Ok,,I HAVE finally tamed the beast.
First was a needle change from a R1173N #3 to a CEL #2. That made one heck of a difference..(For the worse that is).The bike hit even harder when the pipe came on and was way too snappie.But I knew this would be the outcome from what I read on other posts. It was the 1st needle that arrived so I decided to give it a go.
Found the air screw set out too far so I went to a smaller 45 pilot with a/s set to 1 1/2. No change in performance just a better selection of pilot.
Plug chop at WOT still showed lean. Went to a 160 main. I now had a bike that pulled hard from idle to 1/4, hard from 3/4 to WOT and was still to responsive in between.
Changed to a BGL #2 keeping the 45 pilot / 160 main running @ temps of approx 30'c each time. a/s adjusted as necessary.
Boy what a difference. Bike now pulls hard all the way through the throttle range. It is much more controllable in the woods and now has a more usable, friendly power. The hit is no where near as hard yet the bike still pulls the front end when demanded.
It's not perfect yet but getting there.
I'll play with clip positions next time out and from those results I will choose a needle that will give me more flexability for changing weather temps. I feel it could be a little leaner as it does tend to 4-stroke a bit under load.

I'll post results.
Thanks for helping me tame my beast making riding safer and a bunch more fun.
Joe

 

[BucKat]

oh ya...I did get that KIPS problem fixed...
Problem was with the collars. They were worn out too much causing the valves to bind..
Joe