KDXRIDER.NET

First - I want to say "Thanks!" to those who take the time to share their knowledge and expertise. I have been lurking and reading for a few months now and I have learned a ton of information about the KDX. I purchased a 1993 KDX 200 this summer - she's not a beauty pageant winner but she runs strong 99% of the time. I'm the 4th owner and I don't have a lot of maint history on the bike so I'm having to solve problems as I go.

I say she runs strong 99% of the time because I have a plug fouling issue. Seems to occur most often during the warm-up stage - as in the plug will most likely foul 1-2 minutes after I have started up and begun to ride. However, the last plug fouled after about an hour of riding so it fouled while fully warmed up. When the plugs are removed, they are black and wet - so I'm assuming that I have a rich condition that needs to be corrected. I like to ride trails / woods so I might be lugging the bike too much - but I'm pretty confident that I keep the revs up enough to prevent a fouling issue. I've taken care not to go down hills with the clutch out, and I'm paying attention to chopping the throttle after a hard WOT run too.

Anyway - I've spent quite a bit of time researching various plug fouling threads and have begun the process of elimination to hopefully solve the issue. Here's a recap of what I've done:

Changed plug from a B9EG to a BR8ES. The dealer I went to didn't have the EG plug in an "8" so I tried the 8ES plug. My understanding is that the ES has a slightly thicker electrode tip vs the EG which has a sharper pointed electrode. A thicker electrode could lead to a particle getting into the gap, but I haven't fouled any plugs with debris - only wet fouling. If I can find the 8EG plug I'll give it a try. Maybe I'll have to order them online. Anyway, the 8ES is a hotter plug but still fouls...don't want to try a 7 before I exhaust all the other possibilities...

Next up - air filter was checked and cleaned. Still fouling plugs. Airbox lid is still on - however, it looks like the back 1/2 of the lid was cutout and someone screwed a mesh screen in place to keep larger debris out of the air box.

Changed the the premix from 32:1 to 40:1. Still fouling. Although I just found an article that suggests that having less oil in the mix actually makes things "richer" since the "rich" means too much fuel. So I guess I messed that one up and should go back to 32:1...the oil I'm using is Klotz R50 synthetic mixed with premium 93 octane gas.

Tonight I changed the reeds as I had read somewhere that worn out reeds can lead to a rich condition. I really was hoping to find a cracked, chipped, bent or weak reed...but they actually looked pretty good. I changed them out anyway with new Boyesen Power Reeds. I haven't run the bike after that swap since it's late - but I'm not very optimistic that the issue will be resolved since the old reeds looked pretty good...

Tomorrow I'm going to take apart the silencer and clean that baby out...that's on the list of possible culprits...and I need to get a compression check done once I grab a tester just to rule that out as well...

Anyway - next up is the carb...since I had the carb out to get the reeds installed I disassembled the carb to inspect the jets and needle. I also need to make sure the float is set properly and I just found a thread on how to do that - nice!

So - here's how the carb is set up:

Needle: R1172N with the clip on the #4 ring (1 slot lower than middle)
PJ: 38
MJ: 150
Air screw: 3/4 turn open

I think the 1172 needle is stock...and that needle will run richer than a 1173/1174. The one thing I will do today is move the clip higher on the needle to make it a little leaner - I will move the clip up to the #3 slot in the middle. Or should I go higher? Thoughts on going to a 1173?

Not a lot I can do this evening to change jets around. And frankly, I was surprised at the PJ / MJ sizes which I would think are relatively lean jets. I was very surprised to see a 38 PJ...

Last - I've been running here in Ohio around 1000ft above sea level and the temps have been in the 70-90 deg range. It's cooling down now but I don't plan to travel to different altitudes. With a new plug she runs amazing. No hesitations or bogging. Throttle is crisp / responsive at idle. The only negative would be that once she's fully warmed up, she will sometimes stall if I let her idle...I need to blip the throttle a little once she's hot...I think a minor adjustment on the idle would fix that issue...

Anyway - appreciate any thoughts - I'll keep "plugging" away until she's fixed....

Just to get an idea what I'm working with, this is a B9EG plug that has 10-15 min of run time...still works but I don't think it will last long.

Also - I did a compression check and I'm getting 170 psi. The guy that sold me the bike had said that the top end had been done in the past so I guess it's still in good shape. I'll try to do a leak down test soon...

Did you change your carb setup, except for the clip position ? did you follow the inda's jetting guide ? http://www.kdxrider.net/forums/viewtopi ... 105&t=1156
Just asking because plug fouling = bad jetting or restriction at exhaust most of the time..

Follow the jetting guide. Its the only way to get it right. And make shure everything is mechanically sound. Good compression, good crank seal, clean silencer.

you seem to have a good approach to it but the real issue seems to be jetting (most usually is)
the odd thing is the number you gave us are not the stock jets so someone in the last 20 years "jetted" it

do yourself a favor and go through the jetting guide
before you do though, pick an oil, pick a ratio, get a fresh tank and stay with it because even if the bike was jetted spot on for whatever (and wherever) the previous owner rode it might not be ideal for you

Appreciate the replies and the link to the jetting guide. I'll be working through the steps and it will be interesting to see if the PJ or Needle need adjustments. Currently, with a new plug, I am not experiencing any issues in the idle to 1/8th range so the PJ might be ok. The guide did suggest that if your air screw is less than 1 turn open (mine is 3/4 turns open) then you need to go up to the next sized PJ. I'll start there and see what I get. As for the Needle - I went ahead and moved the clip to the #3 slot (middle) and that should lean things out a little for the 1/4 to 3/4 range which is where I typically ride. I'll get a box of brass at some point as I'm probably headed to the MJ for resolution...of course, I have one more thing to verify before I start the jetting process and that is ensuring the silencer is clean and not causing issues...

Again - thanks for the posts. This will take a few weekends as my time to troubleshot is gonna be limited. Since she's running rich and not lean, I'm not too concerned about damaging things - only my pocket book for plugs I am going to get the bike put back together and head out to the GNCC Ironman race tonight in Crawford, IN...plan to ride with a backpack full of plugs in the trail rider class. Or maybe I'll jump into the Super Sr (45+) C class... Once you get the KDX bug it's hard not to ride every opportunity If you're out there I'll be the guy on the side of the track with the plug wrench - give me a rev and a roost as you go by....

Definetely move the clip! Do the whole jetting guide....but move the clip. I am dealing with the jetting on my new to me ( 3rd owner......second knew nothing about maintenance ) 220 myself. But my plugs were wet and not as grungie as yours...... I had to move up to position 1 from 3 to dry out the plug.

I just ordered new jets to change the MJ. If your PJ is too rich it is affecting the entire range. Good luck!

T

You might consider a weak spark, check all the connections, grounds ect. Plug wire.

I'll look into the spark strength - good suggestion. I'm planning to check the electrical system as the bike came with the headlamp wires chopped - so I need a pigtail / socket to rewire the lamp. I'll have to look up the best way to test the voltage / spark.

As a side note - access to the throttle cable on top of the carb is very tight. I have to practically remove rhe carb to get the slide out of the top of the carb. This makes a simple task such as moving the clip on the needle a pain. I'm assuming I have a stock tank - if so, I'm surprised that the tank sits right on top of the throttle cable which makes access tough. Are there some "best practices" to make getting the carb on/off or the throttle cable on/off an easier process? How much disassembly does everyone do when taking the carb out? Thanks again for the posts.

Loosen the clamp on both sides connectin the carb and rotate the carb to the right side of the bike. Change your clip. Rotate carb back. Tighten up both clamps.

T

dude, pull the tank off and you have all the access in the wold

Tried the rotate the carb method - just not enough slack in the cable to get enough rotation so that the slide comes out fully. The tank removal is what I'll try next time. Seems the 1993 tank I have has an extended reservoir on the petcock side which makes things very tight against the carb. Not a lot of room to even get a finger to pull the choke up. Lol.

Anyway - time to suit up for the ride - hope everyone else has a chance to get out today.

Bummer.....sorry it didn't work for you. Maybe the older ones are different than my 2001

I only rotate mine about 45 degrees to get at it.

T

I just had to change my clip position today so I thought a picture might help....mqybe not...but anyway...

Rotated carb 45 degrees....


Out comes the slide....


I am not sure why yours will not rotate enough, but this is something that may need to be done out on the trail and removing a gas tank seems impractical. Anyway hope this helps...

T

Thanks for the pics T...I thought you were rotating toward the right side. The pic has you rotating towards the shifter (left side) of the bike. From your top pic, your petcock has a long extension of metal before the fuel shutoff. My tank extends down into that area which crowds the left side making it difficult to rotate L/R. I'll post a pic later...

In other news...the bike and I survived the GNCC Ironman today...no fouled plugs after 2 hrs of riding! I'll pull the plug and see how it looks tomorrow. The only change I have done was raising the needle clip up one slot to the #3 slot.

Time for a few beverages and shower...this old man took a few spills today...all my fault...this KDX wanted more punishment than I could provide....Lol...

Cool deal! I found moving the clip made a big difference in my plug too. Hopefully your plug looks good. Sounds like a great day of riding!

T

i don't know what the recommendations are for iridium plugs, but I have about 40 hours on one with no issues so far. i believe the po did a really good job on the jetting though.

Thanks Ohgood - As I was saying, the bike runs strong with a fresh plug. Pulls like crazy. I finally took out the plug after yesterday's race. This is the plug after almost 2 hrs of riding - I had a mix of high rpm's and lugging the motor at times during the race. The only change I did was raise the clip on the needle to the #3 slot. I also increased the idle slightly so that it doesn't stall out after being warmed up. I like that the insulator is more of a dark brown color instead of black. However, I still have black carbon around the metal threads. How's this looking so far? Do I run like this or go up another notch to see if the carbon around the metal threads can be reduced?

I should also note that this plug is a BR8EG, so this plug is actually a step hotter than the original plug pic I posted which was a 9EG. So the hotter plug with the needle clip up 1 notch are the changes...

You said your idle to 1/8 throttle response was good, but how many turns out is the air screw? If it's in the normal range keep the PJ. If not change it. It would be great if it was not out enough turns and you needed to go down one size on the PJ. That would explain the plug. In my head anyway... I am no expert.....

If you do not change the PJ I would go up one more spot on the clip to spot 2. See if that helps....


T