What Spark Plugs

[gasser]

Originally Posted by fabulous furry

.the plug is stinky black even with the 162 jet ??
i use 1.5 % maxim castor 927 and tried Klotz and motul esther with no change.my SWM 240tf1 ran better in the days.!

Stainlesscycle is right you are way too lean on the main and too rich on the pilot. 1.5% is 67/1 on your oil ratio. Going that lean on your oil ratio will cause your fuel ratio to be rich will cause wet fouling of the plug unless you rejet your carb leaner to work with that mixture. Start with picking a good oil and using that oil at the ratio the oil is designed for. 927 is a fabulous oil mixed at 33/1 (3%) and Klotz will probably work well up to 40/1 (2.5%) but I would never go leaner on the oil ratio than 40/1 with any oil that wasn't 100% synthetic and never leaner than 50/1 (2%) unless the oil manufacturer recommended it for the higher ratios. Jetting should be easiest for you if you use a 100% synthetic oil and mix it 50/1. The reason is GasGas obliviously jetted the carb for that ratio since it is what they recommend. You might want to go 1-2 sizes smaller on the main (than stock) because of the hot weather but drop it only one size at a time and test till you get it right. As for the pilot you may want to start 2 sizes smaller than stock if you ride tight single track.
One last thing to leave you with - it is improper jetting that causes plug fouling not too much oil. I ran 20/1 (5%) in Bultacos for years without fouling plugs.