Bolt-on cylinder kit and method for increasing the displacement of an engine

A method of retrofitting a motorcycle engine for increasing displacement, the method comprising:

• performing a cylinder replacement including
• dismounting an original cylinder from a crankcase of the motorcycle engine, the crankcase having a crankcase bore diameter of 4.080 inches, the original cylinder having a first cylinder bore diameter that provides the motorcycle engine with a first displacement and an original spigot portion with a first outer diameter, the first outer diameter and the crankcase bore diameter defining an original diametric clearance of 0.025 inch:
• providing a replacement cylinder having a second cylinder bore diameter larger than the first cylinder bore diameter to provide the motorcycle engine with a second displacement greater than the first displacement;
• aligning a replacement spigot portion the replacement cylinder with a bore of the crankcase, the replacement spigot portion having an second outer diameter larger than the first outer diameter of the original spigot portion, the second outer diameter of the replacement spigot portion and the crankcase bore diameter defining a subsequent diametric clearance smaller than the original diametric clearance;
• and
• inserting the replacement spigot portion from the replacement cylinder into the original 4.080 inch bore of the crankcase.

A method of retrofitting a motorcycle engine for increasing displacement, the method comprising:

• performing a cylinder replacement including
• dismounting an original cylinder from a crankcase having a crankcase bore diameter, the original cylinder having a first cylinder bore diameter that provides the motorcycle engine with a first displacement and an original spigot portion with a first outer diameter, the original spigot portion constructed of cast iron, the first outer diameter and the crankcase bore diameter defining an original diametric clearance;
• providing a replacement cylinder having a second cylinder bore diameter larger than the first cylinder bore diameter to provide the motorcycle engine with a second displacement greater than the first displacement, the replacement cylinder having a replacement spigot portion constructed of steel alloy;
• aligning the replacement spigot portion from the replacement cylinder with a bore of the crankcase, the replacement spigot portion having an outer diameter larger than the first outer diameter of the original spigot portion, the outer diameter of the replacement spigot portion and the crankcase bore diameter defining a subsequent diametric clearance smaller than the original diametric clearance;
• and
• without enlarging the crankcase bore diameter following the dismounting of the original cylinder, inserting the replacement spigot portion from the replacement cylinder into the bore of the crankcase.