1996 rm125 piston

[bquiker]

i'm looking for some advice on what might be going on with my piston in my 96 rm125 and really just prformance that it's lacking. i've had my cylinder re-nikisil plated and a prolite piston installed(i guess it has been awhile now though). i've been getting a bogg when i twist back on the throttle from 0- full throttle. i thought it might be my jetting so i checked fmf home page and got the specs for my jetting using there fmf gold fatty. i've got the jets they said, and still same problem. i haven't adjust the needle on main jet yet but i might try that. but i pulled the jug on bike last night and the piston is pitted all around the top edges. it runs ok just not low end response like i need . i was clearing the 100 footer last sat at the track but bike isn't really right with low end i need. i have boyeson rad valve and reeds are fine. after i put it back together last night she'll pull the wheel of ground through 3rd(53t r sproket helps) but when i pulled into driveway off road in 2nd or 3rd i think, i mashed it and boooooghghhgh. let off and smooth easy throttle right back in it or feathering clutch will work sometimes too. also the nikisil plating is showing some groving under the exhaust valves. i got it done at us chrome and it was not cheap and hasn't been a year. i thought this stuff was suppose to be hard as nails. one other thing i want to throw out there is when i run the piss out of it wide open i get alot of crankcase oil blowing out the vent on top of the exhaust valve area of cylinder. i know where the rod to open and close valves comes up form the bottom end it's open to that small enclosed area and then to the vent on top of cylinder, but is it normal to have oil blow out. after i cleaned bike and went down rode i got back my shoe was soaked and engine to. i was on it though, 5th pinned for maybe 100yds. and running out every gear. any ideas would be awesome thanks, brent

 

[marcusgunby]

You have detonation, and it will eat the piston and plating away if not sorted, it maybe you need to jet it richer or use a higher quality fuel and make sure the timing isnt advanced, if you carry on it will blow the engine.