A buddy picked up a XCR 600. He fired it up and it didn't want to idle very well. He pulled the plug wire off one at a time and the center cyl isn't firing. Switched out coils still nothering. Tested all three cyls and have 110-115 psi. Any help would be great. His son can't wait to ride!!
Try a different spark plug. Inspect the ground for the coil/coils. Not sure what year you have but the Ultra style motors had a metal strip as a common ground and the strip would break causing a short.
Having changed coils then the following may not apply but you never know.
Check all connectors for corrosion. Check plug cap contacts to see if they grip the plug tight. You can also unscrew the cap from the end of the wire and see if you can get an arch from the wire end to the motor or plug while it is running. I have seen the wire to cap screw arch and corrode or even the plug wire develop a short. If corroded, clip off a little of the wire and reinstall the cap.
Are you sure it's spark? Harbor Freight sells a cheap in line spark tester that goes between the plug and cap.
Having changed coils it makes me wonder if it's fuel.
Check for spark and fuel. If not that, then get an index wheel and see if the crank has slipped out of phase. Those are pretty notorious for doing that. The three cylinders should be 120* apart from each other.
