This service is for 2005 - 2018 YZ 125 MOTORCYCLE CYLINDER Big bore .

Cylinder sleeve is installed then bored 58 mm. Bore NOW 144cc. 

Use a 58 mm Wiseco Piston on this 144cc Cylinder

send your piston/remove the power valve & studs

Power Valves Must Be Modified/ Recessed to prevent Piston Damage!

We can precision recess your powervlave at additional cost


Head must be  Re-chamfer to work with the Big Bore piston 

Crankshaft modification required.

Crankcase modification required.


This kit requires you to send us your cylinder, head for modification


YZ-144 Big Bore Jug ( 2005 - 2018)

  • Note: Product images only reflect class of products. If in doubt ask before purchasing. Our cylinder sleeves are made from chrome-moly alloy. Our Ports are machined with close tolerance and shapes allowing easy of installation and greatly reduce the need for additional porting after installation.

  • Return and Refund policy. We offer full refund and exchanges within 14 days of purchase. Products must be is same package without damages. call/text or email in advance.