Hi! I am new to this forum and would be greatful to anyone that can help me with the problem I am having with this RM-250! The problem is the bike coughs and chugs when taking off from a start, it has no low end power, sounds like its missing but as soon as the rpms get up it pulls hard. I have rebuilt the carb( set floats, made sure all passages were cleaned and replaced all seals), changed the plug, has fresh fuel, and checked the reed valves. The reeds were staying open a little so I flipped them over (is this OK to do?)and they seem to close ok. The bike will idle ok now but the mixture screw has to be 5 turns out, but my manual says it should only be 1 1/2 turns out. So it must be running lean for some reason. The bike has fresh gas and oil. I had a local shop tell me that it may need to be decarbonized but dont know what this requires, is this just removing the carbon from the piston, head, and exhaust valve thing? If Anyone knows what might cause this problem? Please please help me.
Thanks in advance
Shawn

air leak? but get new reeds...............
What about the exhaust valve, does it need to be cleaned?

Or does the top end need to be rebuilt?