yz125_894 said:
Hey guys i have a 02 yz125 and i have been having trouble with my bike. i have already seized 2 pistons because the jetting was too lean but today it was like 50 so i went down from 440 main jet to a 430 (420 stock). I was riding the bike and it died and upon taking the top end off i looked at the piston and the front near exhaust was melted and the top was melted to. the spark plug was missing the little thing that sticks off of it. the cylinder now has some of the metal on the front and i was woundering if i can just get this honed or do i need to get it replated thanks. (eric you out there?)
I know if I had seized more than one top end due to lean jetting, I would
significantly richen the jetting and never even think of leaning it for a while. Try to richen it up a bit to start off, because worst case scenario there running rich = a fouled plug vrs. running learn = seized top. What oil premix ratio are you running? But in your case, it seems like as mentioned above you may have another problem on your hand. Stock jetting is rich enough as it is and should be in most cases.
If the spark plug is missing the electrode tip (if thats what you are referring to?) Does it look as if it is burned off, or snapped off? A friend of mine had his electrode tip burned off and it sticks straight up, and due to further inspection, his coolant level was low and the bike was overheating easily and wasnt starting when even the slightest bit hot.