Hey folks. I just bought a used 1994 CR250R. The previous owner had it for about 1 1/2 years and never changed the top end out. He did not ride it too often. I took it home and tore into it, compression tested at 170lbs at 1000 ft A.S.L. I pulled the Fatty pipe off to get a good look in the cylinder through the exhaust port. I can see some tan coloring on the intake side of the cylinder wall. Brownish tan like, I can still see the cross hatch pattern there as well. Looking at the exhaust port I see a small shiny spot on the piston between the rings. No carbon build up to speak of at all. The top of the piston looks mint, no carbon. The plug was a nice tan color with no flakes. Bike seems to run fine. Stock carb,jetting is 175 main, 55 pilot with FMF Fatty and Power Core II silencer. When looking at the piston from the front, I can see some wear on the cylinder, some scoring on on the right side of the skirt, right where it travels along the edge of the exhaust port. A thin strip line of scoring along the full length of the piston skirt. I cannot see any scoring on the left side of the skirt in the same area. I cannot tell if this is from a minor 4 pt seizure or not as I have not yet removed the cylinder. Anyone have any comments on this? Maybe I could get a photo with the digial camera and you all can have a look at it.
My gut feel is to put in a new piston and rings, lightly hone the walls and re-gasket. This way I know where it stands. I have no idea how many hours are on that piston. Is there a reason for the brownish tan in spots on the cylinder? What about the skirt scoring? I am thinking that the scoring might have been caused by improper warm up. Riding the bike too hard when cold. I was thinking of putting the pipe back on and riding it for an hour or so to get a real feel for it. I only test rode it, just bought it yesterday. After I get an hour or so on the bike, maybe I look for more wear through the exhaust port and think about a top end rebuild. The reason I am a little confused is, if the top end were in need of a rebuild why would the compression be at 170 psi? So you know, I am pretty experienced with 4 strokes and some 2 stroke engine repair. I do all my own work, including complete bike restoration. I have most of all the the tools I need and have gone as far as completely splitting an XR350 engine for crank and tranny rebuild.
Your comments are appreciated.
Keith
My gut feel is to put in a new piston and rings, lightly hone the walls and re-gasket. This way I know where it stands. I have no idea how many hours are on that piston. Is there a reason for the brownish tan in spots on the cylinder? What about the skirt scoring? I am thinking that the scoring might have been caused by improper warm up. Riding the bike too hard when cold. I was thinking of putting the pipe back on and riding it for an hour or so to get a real feel for it. I only test rode it, just bought it yesterday. After I get an hour or so on the bike, maybe I look for more wear through the exhaust port and think about a top end rebuild. The reason I am a little confused is, if the top end were in need of a rebuild why would the compression be at 170 psi? So you know, I am pretty experienced with 4 strokes and some 2 stroke engine repair. I do all my own work, including complete bike restoration. I have most of all the the tools I need and have gone as far as completely splitting an XR350 engine for crank and tranny rebuild.
Your comments are appreciated.
Keith
