I have a 1996 Xv1100 which will smoke if left to idle or riding on a long downhill stretch with the throttle released. I have removed the top end of the engine and replaced the valve seals. Checked all the piston rings. There is no wear on the bore. Bike starts ok and runs ok but still it smokes after about 2mins if left to idle.
White smoke or blue smoke? White smoke indicates a rich fuel condition. Things that can cause rich running are maladjusted pilot screws, a stuck open or only partially closing float valve, malfunctioning enricher (choke) valve(s), or float levels set too high. A partially closing float valve will cause the fuel level to be too high in the carb, but at higher RPM the motor uses enough fuel to keep up with the extra fuel. At idle the carb floods because the motor requires less fuel. There could be a piece of dirt holding a float valve partially open.
Try pouring a half can of Seafoam in a full tank of gas. When that tank is empty, use the other half of the can at fill up. Seafoam does a really good job cleaning the carb passages and will clear up a lot of these types of problems.
If you do have a flooding problem, chances are that you also have fuel in your oil. The carbs have no overflow, per EPA regs. The excess fuel goes into the cylinders, past the rings , and into the crank case. To check for fuel in the oil, remove the oil fill cap and get your nose down to the hole and sniff. If there is fuel in there you will smell it. If you do find that there is fuel in the oil DO NOT start the bike until the oil and filter are changed and the carb problem is fixed.
Hey thx for your help you're the only one with a brain I've been searching the Internet forever and the people on YouTube of morons nice to see somebody with some knowledge I know it was the carburetors Because sometimes is running fine not smoking and other times and it was very rough it's stalling and smoke is coming out of the top of my crazy everyone tells you it's the Pistons you're the only one with the correct answer Thx so much feel a lot better knowing it's not my head gasket with my Pistons