Bad /Bent Exhaust Valve on Kawasaki Ninja 400 with less than 100miles

This is an FYI for all of the viewers, We recently received a Kawasaki Ninja 400cc engine to build, upon inspection of the engine we found a high leak down on the #2 cylinder, after removing the cylinder head we found a bad/bent valve.


Kawasaki Ninja 400cc with less than 100 miles and it has a Bad /Bent Exhaust Valve , No piston to valve contact (PTV) just the way it was made/assembled at the Factory in Thailand. This created a 20% leak down on the cylinder. This is one of many low mileage Ninja 400cc cylinder head we have found with this issue.

When you are purchasing a $5000.00 entry level commuter style bike , you will need to realize it is just that, for the most part you will get a good bike, a commuter bike , but it is not a track day or a “race” bike.

Spears Racing has been doing these “Commuter” style bikes dating back to the Mid 1980’s starting with the Kawasaki Ninja 250cc and has seen so many short comings for racing in the engines power plants,transmission (Jumping out of gear) and several other areas.

We have seen valve seats pitting around the “seat to the aluminum casting” loosing up on the Yamaha R3 in 2015 loosing compression and went from starting to were the racer needed to push start to it just stopped running.

As you can see , this Bad /Bent Exhaust Valve is one of several we have seen here at Spears Racing building race engines for Club level and National racers around the world.


Spears Racing has been designing and making race products for decades, their continuous committed to excellence to advance as the industry changes. This commitment has resulted in more components specific to certain applications, proprietary products only manufactured for us. Each of these aspects has been put through stringent research and development stages to ensure that our product will exceed your standards.