Zipper’s Sleeper 107″ to 124″ Black w/ Highlighted Fins Big Bore Kit



Zipper’s Sleeper 107″ to 124″ Black w/ Highlighted Fins Big Bore Kit




Zipper’s Sleeper 107″ to 124″ Black w/ Highlighted Fins Big Bore Kit:

This powerful kit by Zipper’s transforms your 3.937″ bore 107″ M8-powered machine to 4.250″ bore 124″ with a drop-on piston & cylinder kit. The Sleeper 124” kit is based around new-production cylinders and pistons, designed specifically by Zipper’s for durability and improved oil control. The new cylinders are then treated to the best precision boring and honing process you can find, as our technicians precisely measure each piston to provide skilled, old-fashioned sizing processes to the cylinders. Mounted in special torque plates, a CNC-hone is used to create a straight and true finish, topped off with brush-finish technology that requires minimal run time for ring seating while providing best power.

This is a hugely cost-effective way to increase the power of the Milwaukee-Eight® engine – with stock heads and a stock throttle body! While your engine is apart, we HIGHLY recommend that you do a full inspection of the cylinder heads for seat or guide issues, and Zipper’s provides new valve seals in the gasket kit for reassembly. If you are not equipped to perform the inspection or repairs to your stock heads, Zipper’s offers these services and more, just give them a call!

This kit represents the basic parts required to turn your 107” into a big-torque 124”. As expected, you will need a high-flow Air Cleaner and Exhaust System, a Tuner to recalibrate or replace your factory-equipped ECM, higher-flowing injectors, and a stronger clutch-pack and slave cylinder to be able to handle the torque. Upgraded injectors are required for this kit (we are using 7.1 gps injectors). Please call for advise on dressing out your Sleeper 124” kit, if you don’t already have a Tuner / Air Cleaner / Exhaust system on your motorcycle.

  • This project requires a skilled technician. It is the responsibility of the person assembling the parts to check all clearances and assembly specifications.
  • We highly recommend using Feuling’s ARP Cylinder Stud kit during install to avoid reusing stretched stock cylinder studs.

Not recommended for Tri-Glide or other three wheel models including conversion due to lugging nature of these bikes.  


Important Information (MUST READ):

*A ThunderMax Autotune System is highly recommended for this product if you do not already have an aftermarket tuner. If you have one already, we can also provide you a recommended base map if you purchase this kit.*

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