200 KX-250 tuning issues....

[GR8FUL_X]

2000 KX-250 tuning issues....

I have a 2000 KX-250 with carb issue. I seem to wet foul plugs on a regular basis. Once the bike is warmed up, and a good plug is in it, it runs great. The next time I go to ride, it fouls 7 times out of 10 right off the bat. I replace the plug, all is well until next time. I run a FMF Fatty pipe, with carb set to FMF specs +or- a 1/4 turn on my carb settings. I run my fuel at 40:1, and the bike makes great power, just a little dirty down low. The plugs always look wet fouled per Eric Gorr's website. Any suggestions? Popular opinion is to rejet the carb.:D

 

[Camstyn]

Stock jetting is very close on this bike, FWIW.
The FMF pipe shouldn't change much. I would maybe go one or two steps down from stock on the pilot.
Maybe tak e the bike in for a leak-down test to check for a leaking clutch-side crank seal.
Here's a starting technique (cold) that never fails, with any bike..

Turn on gas
pull up choke
lean bike over until gas pukes out the overflow
put bike in 2nd gear, rock back and forth 7-10 times
don't touch the throttle
set at TDC and one kick should do it every time unless something is wrong.

 

[GR8FUL_X]

..to last...

Thanks fo rinput. My starting technique is more or less the same thing. It cranks up ,fouls within 2-5 mins. Everything I read leads to the bike running rich. Problem is pilot or main? Crank seal leak is interesting, will check when I tear down for winter maintenance. Just tired of fouling plugs, after a year of fighting with it, I am ready to take action.

 

[Jimmy!]

This is out in left field, but if you've got a rich condition it'll get worse as the motor warms up. If you you are only fouling plugs after the bike has sat for a while, maybe you've got fuel getting past the petcock/float valve & "flooding" the crankcase. This could cause the symptoms you've described. You didn't mention what you are using for plugs either. There's a chance your choice of plug could have something to do with it. Or a weak spark.

 

[Onore GT]

The 2000 KX 250 was definitely a bit rich at lower throttle openings but you might take a look at your reeds before you start any jetting changes, the reeds go away pretty quickly on the KX.

I know there can be some regional differences on jetting but if the bike is still too rich on the bottom after looking at the reeds and you want to try something, here is what I have been running in southern California:

Needle: N3YF pos # 4
Main: 170
Pilot: (std)
Slide: (std)
Air Screw: 2-2.2 turns out depending on conditions
Fuel: Pump 92 , 32:1

I did not have a problem with fouling plugs but it was a bit rich on the very bottom, and seemed a bit lean around 1/8 throttle. To get the desired result I ended up 1 needle leaner (from an E to an F) and 1/2 a clip higher than stock (N3Y). I put in 2001 reeds which seemed to require the bigger main so you might not need to change the main if you have stock reeds.

Depending on how cold it is, I only have the choke on for about 5-15 seconds after I start the bike. After you start the bike, hold the bike at a high idle and turn off the choke as soon as it is warm enough to keep running. Continue to hold the bike at a high idle until you feel a slight temperature change in the radiator. Then clean it out by slowly opening the throttle and letting the RPMs increase until the bike starts to rev more freely. You will hear the engine noise change from kind of a loaded sound to a free revving sound. You will need to do this a couple of times probably, just be sure you open the throttle slowly so you don't inundate it with fuel and cold air. This process should blow any residual fuel out of the lower end. If none of that helps, you could try a hotter spark plug also… Good luck.

 

[GR8FUL_X]

info on jetting...

I appreciate your info. Check this site, these are my basic intentions.
http://www.billspipes.com/tech_tips/jetting/
I have new reed valves ready to install, Boysen. I had intended to check floats for sure. Saw many infernences to that on the web. I did a google search on "kx 250 + jetting tips" and waded on in. Saw many tuning ideas. Bike runs great WFO, just dirty down low and fouling plugs. Since I am taking it apart this winter, thought I might fix some of those pesky things about it I don't like.

 

[Nevada Sixx]

try looking really really close at the wetness on your plug and make sure it's not coolant from a leaky head gasket,, does your bike let out a pure white puff of smoke when you start it?

other than that you may be too rich on bottom, or have a leaky fuel inlet needle, or maybe your cylinder floods from hauling your bike. always turn off your gas peacock when you haul your bike.... is your carb floats level? or is the carb in tilted too far?

 

[GR8FUL_X]

Haven't taken carb apart yet to check anything. Researching what I need to do and check. Bike comes apart in early December. I turn fuel off when I am not riding the bike and for hauling. I have tried different fuel ratios as well. I just want to get it tuned optimally. This issue has been bugging me since last Aug, now it is time to fix it. Sometimes I can ride the same plug for 3 weeks, most times 1-2 weeks. I ride once or twice a week for several hours. I just carry 2-4 plugs with me every time I ride, 30 sec change and off I go. It seems to do it less in warm dry weather.

 

[bscottr]

Tried a different oil?

A friend has a 2000 KX125 and had the exact problem you describe when he used Kawasaki Racing Oil. Switched to HP2, problem solved.

Good Luck.

Scott