Jetting confusion...

[nmilne]

Hi all ... I'm slowly working my way around my new (1997) kdx ... and have the carb in bits at the moment sorting out what the jetting should be. The carb doesn't look as if its been opened before and has what I presume is the standard jetting - 48 pilot and 165 main jet. I've been reading a bit on jetting here and I must admit being a bit lost ... lots of people seem to be running very lean, but then lots of guys are running at altitude as well.

So what I'm looking for is a jetting recommendation for a 97 kdx200 running at approx sea level (maybe up to 1000ft?) with the standard pipe and snorkel removed (but with lid intact, although it has a bunch of holes around the perimeter of the snorkel which I assume is stock?). I'm mainly after optimal response from off-idle.

The bike also came with a FMF gold series Fatty K-35 pipe ... i've heard a lot of people say these didn't come for the kdx, but that's what's stamped on it. I've put the standard pipe back on for now because the FMF is rather dented, especially around the crown of it (probably 15-20mm deep dents). Is this a decent torque pipe and are they easily repairable? Or should I start looking for another pipe? Again, I'm mainly looking for tractable power, not really for snap, at least not at this part of my learning curve....

:cool:
Neil

 

[nmilne]

btw, the temp around here this time of year is around 15-18C, or 60-65F

 

[John Harris]

Lots of threads here on jetting and every bike is different and you have to do it with trial and error to do it correctly. That said, start with 42 primary and 155 main and you will be close enough to ride and fine tune the process. Cheers John

 

[nmilne]

Thanks John - yeah, I've been reading quite a bit, but its almost like information overload. 155 main sounds like the go and I was thinking a 45 slow jet, but might buy both and see how much twidling needs to be done with the air screw. Thanks again.

 

[kmccune]

The first step for a beginning "jetter" is to buy 3 pilots and 3 mains. The first one of each jet being your best guess "base" for your situation from reading and discussing. The other two being one step up and one step down from the first one. Then get a supply of spark plugs, clean and oil your filter and find a nice flat area to do the plug chop.

OK I lied.... first go to http://justkdx.dirtrider.net/ click on" KDX Tech Tips" and then On "Carb Tuning" print the article out and read it and then read it again and then study it :) Then get the jets mentioned above, the mentioned article will guide you to the base jets.

Take your time it really isn't that bad, getting it very close that is. Now some here are more anal ;) then I am about jetting so do this first and then read about perfecting your jetting, but be warned if you go down that road you will be jetting every time you ride....I just can't be bothered with it. I change jetting with major temp changes only, no altitude here to worry about.

Good luck ...oh and let the anal jettersclub begin the flaming :rotfl:

 

[Rhodester]

People have said about me that I was 'anal'....along with something about 'hole'...

 

[kmccune]

People have said about me that I was 'anal'....along with something about 'hole'...

:laugh:

.....and your bike most likely runs cleaner then mine, but I don't mind if you don't. :laugh:

 

[waronwoods]

jetting confusion

I am also confused.... I have been riding my KDX 220 for 2 years without touching a thing on it, and I'm still running the original plug it came with. I have had no problems with any part of the powerband. Yesterday I strapped on a Gnarly Desert+powercore2 and cut half the air box out. took it out for a short ride this morning and it seems to run perfect??? should I worry?

 

[Rhodester]

The FMF pipe will make the bike run richer. You would benefit from leaning the pilot a step and the main jet a step or two (maybe more). The 220 also has a nasty habit of grenading OEM pistons especially when modified for more power. I'd put a wiseco piston and rings in there ASAP.

 

[Green Hornet]

FMF has recommended jetting for the 220 on thier site. There pipe could lean abit. But, when I installed it on my 220 there was no problem. The rich mixture began when I installed the Boyseen Power Reeds. Look at there site for the jetting specs and then go from there. I'm sure you could fine tune it. I put the Gnarly Desert on mine w/Turbinecore 2 Sparkarrester Silencer and what a great Hit it has now

 

[nmilne]

Ok, still struggling with the bike ... I got my wiring sorted and have the headlight and tail light hard wired on now. However the bike still isn't running very well at all. I pulled the carb off and gave it a bit of a clean, put in a 155 main jet but left the stock 48 pilot (the 42 & 45 are on order) and set the air screw at 1.5 turns out. Float level is at about 15-16mm and I set the standard needle on the 2nd clip pos from top. I stuck in a new plug, checked the filter and individually wrapped the cut loom wired with tape to insulate them. Finally I made up some new premix (after dumping the old lot) with motul 800 at 40:1.

First, the bike is still a pig to start. I kicked for an eternity until it finally got started in a spluttery manner. Once running it requires a fair bit of throttle to keep running and only idles with the idle adjuster on the carb turned virtually all the way in. Even then when idling it'll trying a stall from time to time, just bumping up off the point of stalling repeatedly until some throttle is added and it returns to its highish idle. When giving it a handful of throttle it revs but feels flat, not crisp. There's so much throttle wound on to get it to idle that you can't see perceptable change with the air screw, so I let it be.

Stopping and restarting the bike is sometimes easy, sometimes a drama requiring multiple kicking. Once running it will also sometimes start bogging badly, like its starving for fuel. Giving it some throttle twisting action seems to get over it, and pulling the fuel tank cap off doesn't fix it (ie. its not a tank vaccum issue). Plug spark seems ok when kicking over by hand. When trying to get the bike restarted it seems to work best by kicking a bit, then giving it some kicks WOT to clear it out, then choke and try again....

I'm a bit lost at the moment ... any help appreciated ... I'm thinking either the carb needs a good clean out with compressed air or there's an electrical breakdown of some sort ... potentially a bad coil or similar?

 

[m0rie]

Have you checked your carb vent hoses? If they are blocked or pinched they will cause the bike to idle and run poorly. Have you checked the condition of your reeds? If you pull the stock reed cage out and there are still a pair of brass duckbill reed stops on the cage, chances are the reeds are the originals and should be replaced. If they are frayed or chipped they need to be replaced. What did you gap the plug to? You should also pull the petcock off the bottom of the tank and see if the filter screen is clogged.

Let us know,

-Maurice

 

[nmilne]

I had cleaned the fuel filter (which was pretty dirty) and pulled the reed block out. Yep, they're the standard reeds allright, but they seem to still hold tension very well and are in good condition to the naked eye (see http://vsmr.net/albums/bitsnbobs/kdx_reed_block.sized.jpg). I'll recheck the plug gap this afternoon and double check the vent hoses, although they did look ok. Think I'll go back to stock jetting and slide clip until I get the basics worked out.