99 Kdx 200 <10mpg

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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FosterH0ME
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99 Kdx 200 <10mpg

Post by FosterH0ME »

So despite new top end (149psi compression), cleaned KIPS, rejetted according to fmf website for turbinecore pipe 155/48 1.5 out on air screw with no air box lid, new fuel line, replaced carb gaskets, replaced float valve,new reeds, new exhaust flange gasket, new spark plug I am still getting terrible mileage out of my kdx. I just want to go out and ride. I don't need anything amazing but it would be nice to be able to take the bike to larger off road areas without needing a fuel tanker to accompany me. Anyone have any additional ideas for places to look to improve the mpg? I am about ready to list the bike for sale in an effort to acquire something less thirsty.

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Julien D
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Re: 99 Kdx 200 <10mpg

Post by Julien D »

Jetting according to the numbers on a website is a mistake. Jetting is a process, no real shortcuts there.
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FosterH0ME
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Re: 99 Kdx 200 <10mpg

Post by FosterH0ME »

I'll try out the procedure from the jetting section and reassess. Would you expect mileage to be drastically different though? Bike runs good and starts first or second kick .

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99 Kdx 200 <10mpg

Post by Davenay67 »

Are you getting a lot of spooge?

That pilot jet sounds big, but like Julien said, the jetting is a process that you need to do on your individual bike. My KDX spooged like crazy on a 45 pilot, but simply going down to a 42 dramatically reduced the amount of spooge.
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Re: 99 Kdx 200 <10mpg

Post by JL4049 »

I get 125 odd km from a full tank with similar jetting, riding steep hills and snotty single trail with a few short gravel road sections, I've found that raising the float height to 19mm (measured with the carb upside down) has improved my economy, most of my previously excessive fuel use was spillage from the overflow. I came to this conclusion due to the ends of the overflow pipes being wet with fuel after anything other than smooth riding. Now they only show fuel after a crash or jumps/ruts.
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Re: 99 Kdx 200 <10mpg

Post by FosterH0ME »

I am getting a fair amount of spooge and my float height was about 15mm when I checked it so maybe I'll move that up as well and see what impact that has.

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Re: 99 Kdx 200 <10mpg

Post by Julien D »

It's likely that 155/48 is still pretty rich, but it will depend on the actual bike, your riding style, your elevation, and climate.
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99 Kdx 200 <10mpg

Post by Davenay67 »

An issue I had when my KDX was getting poor MPG was the jet block gasket. After replacing this, the running of the bike instantly improved and I was able to jet properly. I am getting much better mileage since then.
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Re: 99 Kdx 200

Post by FosterH0ME »

Elevation is typically 0-2000, gnarly to flowing single track with medium clutch use and mild-moderate frequent hill climbs throughout the ride. I have never checked out the jet block gasket and based on the threads I have found on here and my cleaning methods, chances are good there is nothing left of that gasket. Thanks for the input!

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Re: 99 Kdx 200 <10mpg

Post by Julien D »

Oh yeah, a leaky jet block gasket will cause it to run super rich. You're jetting should be acceptable (read: safe) for your described elevation and riding. There is always room for improvement there.
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Re: 99 Kdx 200 <10mpg

Post by MotoArts »

My 220 gets horrific gas mileage also. New jet block gasket, 42 pilot (up from the as-purchased 38), top end and KIPS check, etc... It starts, idles and runs like mad on the mainjet, but has an undiagnosed low/midrange stutter. I have zero spooge with either Lucas or Maxima 32:1, and recently switched over to Amsoil 100:1 in an attempt to cure the stutter.

Bike literally gets half the mileage of my son's CR250. It is by far the worst mileage that I have ever witnessed with 40+ bikes owned over the years. It probably goes through a tank full in 2 hours of casual mixed riding.

Float height readjustment (for the 3rd time) will be next, as I do notice the overflow is wet often. It may be my stutter issue too, but I doubt it.
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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Re: 99 Kdx 200 <10mpg

Post by Julien D »

Float height can cause that stutter, as well as too fat of a pilot. It's unlikely that you'd need to go up to a 42 on a 220, but every bike is different, so I can't say for sure.
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Re: 99 Kdx 200 <10mpg

Post by MotoArts »

I've tried moving the needle clip up, down and mid... makes zero difference. Airbox lid off/on makes zero difference. Kind of shocking to me, even with the 38 pilot, which I assumed was too lean especially with a PC pipe. Plug doesn't say so... it actually looks great. Never fouls, although it sounds pig rich when cold. Definitely does not read "lean" either... it's the damnedest thing I've ever ridden.

Weirdest thing about it is when I took the top end off for inspection, the plug was correct color, but the chamber and piston crown were totally carbon free (with 32:1). No signs of lean scuffing/seizure on the Wiseco. Crown and chamber were actually shiny, like they were wet. I assumed antifreeze steam cleaned the components from a bad/reused head gasket or crack somewhere, but found no other evidence. I even grossed my son out a little when I lick tested the head looking for the obvious antifreeze flavor, but got nothing. :tonqe: Worse yet, nothing changed there after inspection and new gaskets.

I have a borrowed CDI from a local guy, will try it this weekend since it's so easy to swap. Then I'll drop the float if that doesn't change anything.

Check out http://www.dynotronix.com/ . This gentleman is a local friend of a friend here in Pittsburgh, and he's the one who really got me thinking towards potential bad values in the CDI box components. The YZ/IT/WR blue bike on his site has some of my donated WR200RD parts on it. It's a really cool budget build and is a test mule for Dynotronix. At the time, he wasn't interested in dissecting the unit on my Kaw, preferring to stick with the early Yamahas for the time being. If my unit does check out bad, I will donate it to him in hopes that I can convince him to "go green" :cool: .
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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Re: 99 Kdx 200 <10mpg

Post by MotoArts »

FWIW, the CDI swap on my bike netted no change.
It still had one ignition "ground out" during the test session, where the engine shut off like the kill button was pressed for a half second, while under power. So, my bike still has what I'm assuming is an ignition fault somewhere (source coil/ignition coil/bad ground/broken wire). Still convinced that my fuel mileage issue is either slightly too high float level, or inefficient/inadequate/erratic spark or spark timing.

I'm about out of options :hmm: :cry:
'97 KDX220, '84 YZ125, '81 YZ250, '78 RM250C2, '80 RM100T, '04 KTM 250SX,
'82 Yamaha Seca 650 Turbo, survivor
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