i found out that i have a problem with a cylinder on my engine , due to the time that the engines wasn't running (around 10 years ) i have corrosion in on of the cylinders . i consulted my mechanic and he told the best solution is to go on a bigger size piston and machining the cylinders now the problem is i need to find out which yamaha engine has a piston that fits my engine. i have an xs400 yics 1984-85 . anything knowledge will be appreciated