93 KDX 250 Fouls sparks

[bujas]

Hi,

Have a 93 KDX 250 that when i ride in light throttle it fouls sparks but when ridding in full throttle it has no problem, does anyone as idea on what could be?

Best regards

José Pedro Borges

 

[Crimeidy26]

Yep. Too big main jet. These bikes stock jetting it WAY to rich. Make sure your air filter is cleaned properly and go down on the main.

 

[exbee]

I've been re-building a '93 KDX 250 all winter and just took it for it's first proper ride today....it really rips, I'm pretty happy with it's performance. The jetting I'm using is what I've determined was best from research on this site and others. I'm using a 158 main, 38 pilot, and an R1367H needle on the 3rd clip. When I rode it before the jetting changes it didn't run very well so new jets is a must. The spark plug Im using is a BR7ES.

 

[6pac]

Hi,

Have a 93 KDX 250 that when i ride in light throttle it fouls sparks but when ridding in full throttle it has no problem, does anyone as idea on what could be?

Best regards

José Pedro Borges

To me it sounds as if the needle clips in the wrong position, if the bikes ok at full revs it means the main jets ok.
Move the clip "up" to the next notch, this will let less fuel and more air into the cylinder which will lean out the mixture in the mid rev range.

Let us know how it goes ok.

 

[bujas]

What clip?
The bike was recently on a Kawasaki representative and they changed the main jet and pilot nad the problem remained.
Could it be the coil-ignition that generates a small spark in low revs?

 

[exbee]

I spoke too soon about my KDX 250... I fouled a plug yesterday too. I was riding really slow and not revving it due to the slower rider on a small bike that was with me. Mine is jetted correctly and works great when you ride it hard...apparently they don't like to to be ridden slowly at low revs?? I thought I was blipping the throttle frequently but it must not be enought. Is this how yours fouled bujas?

 

[bujas]

I spoke too soon about my KDX 250... I fouled a plug yesterday too. I was riding really slow and not revving it due to the slower rider on a small bike that was with me. Mine is jetted correctly and works great when you ride it hard...apparently they don't like to to be ridden slowly at low revs?? I thought I was blipping the throttle frequently but it must not be enought. Is this how yours fouled bujas?

Yes, is precisely the problem i have with mine.

 

[6pac]

What clip?
The bike was recently on a Kawasaki representative and they changed the main jet and pilot nad the problem remained.
Could it be the coil-ignition that generates a small spark in low revs?

Sorry, I didn,t explane myself very well.
If you remove the top of the carb and lift out the slide, the needle is connected to it.
If you unhook the throttle cable you can now take the carb needle out.
On the needle there will be 5 notches and & one of them will have a little cir clip in it.
To lean the air/fuel mixture, move the cir clip to the next notch up.
Heres a couple of pics to show what the needle & slide look like.

 

[Matt90GT]

First off is this a US model or a SR model? completely different bikes!

Second if you have a US model, you need the different slide also.

 

[glad2ride]

Jetting, jetting, jetting.

...assuming that all parts are in good working order (cleaned and oiled filter, reeds in great shape, cylinder, piston, rings, power valve system, exhaust, etc.)

 

[julien_d]

Sounds like pilot is too large, or needle setting is too rich. You SHOULD be able to lug that engine all day long without fouling a plug.

You're sure crank seals are good?

 

[exbee]

I know this isn't my thread but I have the same problem as bujas so hopefully he doesn't mind me asking questions in it...he can benefit too..
Anyway, after I fouled my first plug the other day I dropped my needle from the third clip to the second clip and the bike ran excellent for a day or so until I fouled another one very shortly after I started riding today. I've got one needle position left so I guess I'll just lower it all the way and hope for the best. When I'm riding the bike it pulls extremely well and there are no hesitations or bogging at all. The only sign that anything is wrong is when it suddenly dies and won't re-start. I've done everything recommended jetting-wise other than change the slide to a #6. As I understood this isn't completely essential anyway. What else could be the problem? Why does the bike run so well otherwise? Any ideas?

By the way: freshly cleaned & oiled filter, new Boyesen Power Reeds, freshly cleaned carb, recent Wiseco piston & rings by previous owner, not sure of the condition of the KIPS but seems fine

 

[dmaegan]

uhm are you watching your tranny oil levels blown seal on clutch side of crankcase will let tranny oil seep in and it will cause the plug to foul and it would be worse at lower rpms

 

[bujas]

Mine is not the US model.

 

[Tom68]

Mine is not the US model.

Haven't got my figures here for my Australian delivered steel tank oil injection model but have posted them up before so you should find them with a search. But I think standard jetting was fine on ours.

 

[Winkel]

If the bike starts easily without the choke, try dropping a couple of sizes on the pilot jet.

 

[mudpack]

What premix oil are you running and at what ratio??

 

[exbee]

I've only been using Amsoil mixed at 50:1 in mine
Could it be my warm up procedure? I start with the choke (although it will start easily without it) and shut it immediately, let it idle for 2 or 3 minutes then go. Should I let it warm up longer? Less time? Rev it?

 

[Winkel]

Since you say it starts easily without the choke, I'd say you're too rich on the bottom end. Try dropping two sizes on the pilot jet and see what that does for you.
Winkel

 

[exbee]

I've got a 38 pilot installed and all of the research I've done on the bike tells me that's what works best at sea level or slightly above. I don't even know if I've seen a smaller pilot than 38 recommended for any condition. I guess it's worth a try. I still haven't dropped my needle down to the last clip either, maybe that will help. Could the air screw setting be causing this?

 

[6pac]

Could the air screw setting be causing this?

Yes it could, the air screw works alongside the pilot jet to control idle mixture.

To set up the air screw try this, it only takes 5 minutes.

Get the engine up to normal operation temperature
Set the Air screw to about one & a half turns out.
Now turn the "tickover" screw clockwise to set the tickover at a fast idle (About 2000RPM)
Right, now the bikes reving turn the "Air screw" in any direction, the revs will either slow down or speed up. You are trying to get the engine running as "fast" as possible.
When you,ve achived this your idle mixtures now set to its optimum level.
Now slow the revs back down on the tickover screw.
With the bike now ticking over at a slow idle, snap the throttle fully open, the revs should go up smoothly with no spluttering or hesitation & the engine shouldn,t stall.

 

[exbee]

Thanks 6pac,

I dropped the needle all the way down and adjusted the air screw and it seems to rev cleanly from idle now which it didn't before. Went for a 2 hour ride yesterday and the bike still worked great only I didn't foul the plug...I'll keep my fingers crossed that it's leaned out enough now!

 

[6pac]

Nice one exbee, just keep checking the plug colour for a while to make sure you haven,t leaned it out too much.

 

[f4cem4n]

hey!

i come from germany and my friend bought a kdx 250 from 1993 as supermoto.

But the kawa runs like a bike with 10ps and i think the kdx has a throttle...

in germany i get no informations about the bike because it official dont be sold here.. i think its a import from us..

can you tell me what for a thottle is fit in and where ?

Thanks and gn8 ;)