Top End Engine Build

Most of an engine’s ability to increase power output over a stock unit is contained in the cylinder head.

Modern sport bikes engines have thoughtfully designed intake tracts and combustion chambers that are quite good at making power and according to most organizational rules, which can not be modified from stock.

Increasing the compression ratio of an engine by machining the gasket surface of the cylinder head is where most of an engine’s power increase comes from. Compression ratios can also be increased by machining the engine cylinder deck or changing the thickness of the head gasket or a combination of the mentioned. Careful measurement of the piston to head (squish) must be taken to avoid collision of the moving parts. While the cylinder head is disassembled and being machined, it is recommended to have a valve job performed to give the valve seat better flow and sealing characteristics. Once the cylinder head has been machined and thoroughly cleaned, it is time for reassembly. Careful assembly of the cylinder head involves checking valve spring height and pressures as well as setting the valve lash for proper clearance. After the head is assembled, a new head gasket is fitted to the cylinder and the head is installed and torqued to proper specifications.

Next is installation of camshafts and adjustment of cam timing. After cam timing procedures are complete, it is time to seal the engine with the valve cover, install spark plugs and the engine is ready to install in the chassis.

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Bottom End Engine Build

The bottom end is disassembled after the cylinder head has been removed from the engine. While the factories do a fine job on assembly, they leave a few small details to be taken care of.

Oil clearances can be carefully set at a higher clearance, oil pumps can be modified and things like ceramic transmission bearings can be installed to “free up” minute inertial and frictional power losses.

Also in the bottom end is the clutch. Most modern bikes come with a back torque limiting clutch from the factory that is set very tightly to minimize premature wear on the street. These clutches have to be adjusted or reworked to take advantage of their capabilities.

Other modifications on the bottom end can include bead blasting piston crowns, checking piston to cylinder wall clearances and changing/setting if necessary, oil pump and oil pressure relief valve modification for changing pressure output and transmission modifications.

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