I continue to get black oily "stuff" from my spark arrestor. I have switched from a 150 to 148 and 48 to 42 slow jet. I have repacked my spark arrestor. Moved the needle jet up a notch to lean and put in a new air filter. I am running Castrol tts at 40:1. Running NGK b9eg spark plug. This combination produces a light brown spark plug with slight oil in both high and low RPM. The 1994 KDX 200 runs great, but the oil mess on the back fender and wheel drives me crazy. I have tried other oils with the same results. I have gone from 32:1 to 40:1 with no apparent difference in amount of "spungie" mess coming from my silencer. With Castrol tts full synthetic oil it only smokes very little under a heavy load or full excelleration. PLEASE HELP!!!!
If its really driving you nuts, get a four stroke. All 2 strokes do this, it is, after all, a 2 stroke. If it's dripping on the swingarm, etc... try putting some high temp silicone around the silencer/pipe junction to eliminate that, and if it's the stock SA, drain it. This should help, but just keep in mind that it will always smoke/spooge.
Oils are different. Some worse than others. For most of two years, I haven't had drip/spooge one. Nada. Zip. .
BTW..re: 'Moved the needle jet up a notch...'
That would be RICHER! You probably know that...but it's been a source of confusion before!! Clip positions are numbered FROM the top (non-pointy) end. Moving the clip UP leans the needle, moving the needle UP richens.
Clip position #1 is most lean, #5 (or whatever your needle has for clip positions) is most rich for a particular needle.
I would switch to a 8 heat range plug. I had alot of spooge too no matter how I rejetted my CR it still had spooge. So I switched from a BR9 to a BR8 and now run Maxima superM and have almost no spooge at all.
40:1 is less oil per given volume of gasoline than is 32:1.
Less oil=more gas, so 40:1 is RICHER A/F (air/fuel)wise.
Don't confuse the two. You don't change your A/F ratio by tweaking the premix ratio.....well unless you're doing it for a reason and you know what that reason is.
The terms 'rich' and 'lean' are not generally applicable to premix ratio.
all 2 strokes will slobber somewhere out of the exaust sooner or later, I too would go to an 8 ngk instead of a 9, the nine is a bit cool. (have also had good luck in the past with champion RN2C and found it to be just slightly warmer than an ngk 8 but not as hot as a 7, nice in between plug) If you are getting no spooge at all you are either running the bike real hard most of the time and burning off the excess oil or you forgot to put oil in the gas.
I would run a br7es or 8 plug and 50:1 unless you're hard on the throttle alll the time. 50:1 is less oil but makes the air fuel ratio richer than 32:1. 2% oil versus 3% oil or more correctly 98% fuel versus 97% fuel. The main cause of spooge as it is called is low combustion temp so the oil isn't burning in the combustion chamber. The usual cure is to lean out the air fuel ratio to increase the combustion temp and get a clean burn. To lean and things get to hot and you are likley to stick a piston. To rich and you get slobber. If you ride a lot of tight and technical trails it can be a challenge to get rid of the spooge and keep the throttle response.
Somthing doesn't seem right about your jetting though, if the bike has a 35mm carb a 148 sounds way to lean, most of the earlier kdx's I know prefer a 155/160 main, a 45 or 48 pilot and the stock needle in the mid clip. Whats the altitude and temp?