I have a 02 KX125 and I seem to get a lot of burnt oil coming out of the exhaust. Enough so that it is running down the underside of the exhaust and dripping onto the swingarm. Is this normal? or is my fuel mixture off?
I run Amsoil Synthetic at a 40:1 ratio with standard gas.
A 40-1 mix should be ok that is 25ml of oil - 1 liter gas. If you want to stop the spludge you will need to repack the silencer as it will be soaked in oil. If after doing that the problem persists your jetting is out
You are definitely running a rich “mixture”, but don’t confuse this with your fuel/premix “ratio”.
As MXSparx said, it sounds like your jetting is too rich. Try down sizing your pilot jet and raising the clip on the needle one position.
As Mr. Sparx has indicated, repack the silencer. I would also suggest a new spark plug. Further, make sure that your airfilter is clean as this too will cause a rich mixture.