Modify Govenor

So we have this completely stock GX160 that needs a little extra power.  We modified the stock exhaust and stock air filter assembly as well as added some compression.  Removing the govenor is a great way to add performance to these engines however for this application we need to keep the govenor.  So we are going to show you how modify the govenor spring in order to increase the engines max rpm.
The govenor typically limits these engines to 3600 rpm.  Here you can see our engine reached 3840 rpm.  
We remove the stock fuel tank for easier access to the govenor parts.  That elbow shaped arm on the right is connected to the internal govenor mechanism.  The internal mechanism has weights attached and spins off the crank.  At a certain rpm (about 3600) the internal mechanism pushes on the arm causing the end of it to pull away from the carb.  This movement begins to close the throttle on the carb via the rod you see attached between the arm and the carb.  As the throttle closes the rpm comes down and that's how the govenor manages the rpm.  We modify the govenor spring which puts resistance on the internal govenor mechanism.  The more resistance the more rpm the engine will see before the govenor kicks in.  
We remove the govenor spring and prepare to shorten it using some needle nose pliers.  Making the spring shorter will add spring pressure.  This will require more rpm before the internal govenor mechanism can override that spring pressure and start to close the throttle bringing rpm back down.  Here you can see our stock GX160 spring is about 4 1/2" long.
We made the spring about 1/4" shorter.  
With our shorter govenor spring installed it's time to install the fuel tank and check the rpm. 

As you can see our rpm has gone up from 3840 to 4940.  With these few modifications we've been able to increase the performance of our GX160 while retaining it's stock look and reliability.  

Note:  Use caution whenever modifying the govenor.  These engines were designed to run at 3600 rpm.  When you increase the rpm potential you run the risk of damaging your engine.  The biggest concern here is the stock flywheel which is not rated for high rpm.  We have billet flywheels available for this purpose.