Ok...Yes, this is my first 2 stroke i have owned, but i do know how to keep it on the pipe, etc. Well...let me start by giving all the specs. FMF pipe and silencer, UNI air filter with air box lid in tact, 240 main jet (stock??), and needle clip position 2nd from highest, and 50:1 mixture with Klotz Supertechniplate. Well, the problem is that when we put a new plug in, it runs really good, and it very fast. But usually the next day when we go to start it, the plug will be fouled. I did a wide open plug check with a brand new plug, and if came back to be a light black on the electrode. After we do a couple of normal rides on it, the plug is a very dark black. I know it sounds rich, but i wouldnt think i would want to go much leaner on the jets or the mixture. One of my old fouled plugs had been sitting out for a while, and i took a wire brush to it, and now it sparks. Please help with any kind of help..we do not know what else to do.

 

Don't lean out the main jet or mixture if you're getting good results on a wide open plug chop. I would check the needle and make sure its not worn out. If its the stock needle from 87' then it's definetly time for a new one. I would also check your air screw and maybe lean out your pilot jet.

 

The needle and needle jet wear out on those carbs and cause problems. Also like thesb said see if the carb drips gas out of the overflow when setting. The petcocks also have a tendency to leak past. Start by checking to see if the petcock leaks, then the float needle and seat. If they seem OK, you need to put a main needle and needle jet in it. If the plug turns very dark then it is rich but you wont be able to fix it until those 2 parts are put in. Remember you read a spark plug at the BASE OF THE CERAMIC. Look for a ring there. You might have to use a light or even cut away the threaded part to look at it. That is where to accurately read a plug. Many people look at the tip of the ceramic and that is incorrect. Hope this helps,Bubba

 

When you check the plug color try get tan to a cardboard brown....at least thats what I was told.

later
Superstar