Cylinder Head Service

The CRF300L's stock cylinder head leaves a lot to be desired. Sloppy casting, non-concentric valve seats, and other shortcomings are addressed with our CNC porting service, which includes a 5-angle valve job and head resurfacing. 

The process starts with fully automated sculpting of the intake and exhaust ports. The combustion chamber also gets contoured. Then, the stock 3-angle valve seats are given a 5-angle profile. Total flow (measured in CFM) is increased by an average of 12 percent with this mod, increasing power across the rev range, but especially in the midrange (see dyno chart below). We have a specific Stage 3.5 ECU tune to match this setup. 

Use with stock components (new valves are recommended) or opt for Valvetrain Upgrades. 

Options explained: 

• Bare head: Send us your bare head with cams, valves, rockers, thermostat, and thermo sensor removed and we'll swap it for a pre-ported head. Essentially, you're submitting your head as a core. Please include cam holders and bolts with the head as they're a matched set. Turnaround time is typically 1-2 days. Please specify your bike's year when ordering. 
• Assembled head: Send us your complete, assembled head and we'll swap your parts onto one of our pre-ported cores. Please note, we will not install used valves into a freshly machined head — you must supply new OEM valves or purchase the Black Diamond Valve set. Assembly includes new valve seals and setting the valve clearances. Turnaround time is typically 1 week. Please specify your bike's year when ordering. 
• Replacement bare head: If you want to retain your stock head for whatever reason we'll ship you a pre-ported bare head (with new valve seals included but not installed - they go on after the spring seat is set on the guide) that you can swap your ancillary parts onto. Please specify your bike's year when ordering.