aryr

Just a add-on in 5th gear can run it to 6500 PRM = 55MPH but thats it if I shift to 6th gear it drops to 5000RPM = 50 PRM & no more power

55 @ 5000 RPM the plugs coil wires & coil wire end are new from yamaha the throttle is open all the way

Have a 1980 XS400GS @ high speed 50-60 it loses power i.e. run @ 60 for a minute then drops down New plugs,wires & had Carbs Cin'ed