The best way to add performance and maintain reliability on your 4st. Motocross bike!!
There are lots of ways to add performance on you bike. You can use a High Compression Piston, Big Bore kit or up-grade your Cam Shaft. The problem all these mods will work but can shorten engine life or increase maintenance. One of the easiest ways is during your next top end think about performing a valve job (replacing valves, seals, deck cylinder head and matching the valve seats), since you have the head is already off. It’s time to service the cylinder head on your 4st. motocross bike. You can bring back the lost power and maybe find a little more power and still maintain the reliability. A CNC valve Job is your performed on your cylinder head is the best choice.
What is done to the head? First a CNC 5 angle performance valve job is performed. By cutting the seat into 5 different angles this adds a radius to the valve seat and will allow the head to flow better which increases power. The valve job also allows the valve seal perfectly with the valve seat. Eliminating power loss due to a poorly sealed valve. Then the cylinder head surface will be decked the ensure that the head is straight, and this allows the head gasket to properly seal. Decking the cylinder head makes also allows squish to be tightened up slightly and will slightly increase compression. The last thing to do is install new valves, seals and reset valve shims (clearance) to finish off the cylinder head, ready to install.
Optional Services: Beryllium Copper seats can be added. Works with titanium valves to help heat transfer and helps increase valve life.
Cylinder head porting will help with additional performance gains.
I have a few before and after pictures of cylinder heads. Take a look at what we can do to your cylinder head
Before 2020 YZ250F Badly Damaged (Jumped Timing, Broken Valves)
After - YZ250F High Performance 5 Angle Valve Job with Beryllium Copper seats