I got this bike cheap; 1992 RM 125 in fair running shape.
I thought it had a stock piston because of the single ring vs. Wiescos two ring top end replacements and others I saw..
Just had notice the ART inside the piston, which is a Pro-X piston. They claim to have from Standard and A thru D pistons in like 0.002 increments; while Wiesco are think 0.005 or 0.010 increments. Cylinder had zero seize marks and the combustion chamber is a shoe polish brown; a bit rich. No carbon buildup; a minor amt where pipe/cyl meet.
I assume standard has no markings; which I cannot find any and the remainder are, but where? Top of piston like others?. I've cleaned the top gentely with no markings.
Or does Pro-X have a certain spot they letter their pistons other than crown? Ring had no markings like some OEMs for top of ring specific ones..
Cylinder doesn't appear to have even a scratch mark or is a pressed sleeve; comb chamber had a shoe polish look, a little bit rich. I was real surprised cyl was so clean that could still see crosshatch marks while powevalve was in pretty good shape; no carbon buildup like the head or trimming it to fit a pressed sleeve.
Also have a TMX Mikuni flatslide. The 17mm float bowl holds the bowl in place only.....but I also see what looks like a place to put two small screws close to the float bolt. My eyes aren't good, but looked like threads the same as the four corner tiny screws on float bowls of Keihins and newer carbs..
The point of where it looks like small screws should go in, it doesn't leak fuel; that puzzles me. Yet, when cold, no start, carb/brake cleaner on plug, put bit of WD and starts while revving way too high. Took carb apart is where I noticed what looked to be 2 screws missing despite the 17 mm holding the whole float. Stock jet were there... Reinstalled carb w/o where I think 2 screws go, it started with no 5 grand idle last time..
Pipe, Mr. Newmann, FTE, Pat327; those that can remember, I'd sure be awful greatful like if you know what I'm talking about with the carb and I've had horrid luck just me with Wiescos; and just have never liked them; their kits are more expensive for a $400 buck bike that I wish I could redo, but cannot. Needs a rear knob too...burb.
Thanks a ton for any help on the carb, piston ID location and anything else that sounded stupid at 3 am Pacific whatever Time; fall back; spring forward..