How to identify and replace the motorcycle cylinder block due to strain or wear?

Date:2021-01-05 Hits:

The cylinder block, the cylinder head and the piston assembly form a space for the compression, combustion and expansion of the combustible mixture, and the cylinder block guides and transfers heat to the piston assembly. Some motorcycle owners use inferior engine oil for low price, or do not change the engine oil for a long time, which leads to the decline of engine oil quality or the decrease of engine oil stock, resulting in cylinder pulling or sticking, causing serious damage.


Cylinder wear is divided into normal wear and abnormal wear. Abnormal wear is usually caused by improper maintenance, which is characterized by serious scars on the inner wall of the cylinder. The normal wear cylinder is the upper big lower small inverted cone. The inspection of cylinder wear usually adopts the inner diameter measurement method and piston ring opening clearance measurement method.


In order to restore the power of motorcycle, it is generally necessary to replace the sleeve cylinder components, either the standard size sleeve cylinder or the power sleeve cylinder. No Moku, no modification!


Let's take a look at the assembly and disassembly process of the engine block and piston.


1、 Remove and inspect the engine sleeve assembly


① Remove the cylinder block and piston assembly from the crankcase


As shown in the figure below, gently tap the cylinder block with a rubber hammer to separate the cylinder block from the crankcase.


Remove the piston pin circlip from the piston pin hole with pointed nose pliers (block the crankcase opening with clean cloth); take out the piston pin and piston assembly from the small end of crankshaft connecting rod;


② Check the cylinder block and piston assembly


As shown in the figure below, the external structure of piston assembly and piston pin.


Measure the wear of piston and piston pin with external micrometer (external diameter of piston, 49.975-49.995mm, limit value, 49.90mm;


Inner diameter of piston pin hole, 13.002-13.008mm, limit value, 13.005mm);


Piston pin (outer diameter, 12.994-13.000mm, limit value, 12. 98mm)。


When the wear of piston assembly exceeds the maintenance limit, it should be replaced in a complete set (piston, piston ring, piston pin, piston pin circlip).


Check the inner diameter of cylinder with inner diameter dial indicator (standard value, 50.005-50.015mm, maintenance limit, 50.05mm);