How to De-govern an Engine

How to De-govern an Engine
Warning: Any modifications are performed at your own risk. This guide is for information only.
Prokart Engine Parts accepts no warranty for damage to engines or to self as a result of following
the information in this guide.
In order to de-govern the GX160 or GX200 engine you will need the following tools:•
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10mm socket
12mm socket
13mm socket
17mm socket
Torque Wrench
Piston Stop
Long nose pliers
Drill and 8mm drill bit
This guide assumes that the engine is brand new, if not remember to drain the fuel tank and oil
from the engine!
First start by removing the exhaust, air filter and cover, fuel tank, valve cover and spark plug.
The next stage is to remove the fan side cover and pull start assembly. There is no need to
remove the pull start assembly from the fan side cover. Unbolting the four 10mm bolts which hold
the fan side cover onto the engine block will remove the complete unit. You can also unbolt the
ignition coil at this stage.
Now that the fan side cover has been removed we now screw a piston stop into the spark plug
hole and turn the engine over until it rests against the piston stop. We can now loosen the nut
holding the flywheel and fan onto the crankshaft. We will not remove the flywheel at this stage
but just loosen the nut. The piston stop ensures the engine will not rotate when loosening the
flywheel nut. Warning, the flywheel nut is torqued to 54ft.lbs so you may need an extension bar
on your socket set to loosen the nut.
The next step is to remove the Side Case Cover (the clutch side). The Camshaft, Cam Followers
and the Push Rods may fall out at the same time. If not remove these parts setting them to one
side.
When you have removed the side case you will be able to see the parts that need to be removed
from the engine. These include the plastic gear at the top left corner of the engine and the metal
arm coming from the top of the crankcase cover.
The next part to remove is the Plastic Air Cleaner, Throttle Linkage Arm and Carb from the
cylinder head. Again, there may be some fuel in the car so take care when removing.
We can now unbolt the 4 Cylinder Head Bolts and carefully remove the cylinder head. Take care
that the small Exhaust Valve Rotator on top of the Exhaust Valve Collet does not drop out and get
lost.
The next job is to remove the Piston and Con Rod. To do this you need to unbolt the two bolts at
the bottom of the Con Rod (Big End).
Once these have been removed and the rod cap removed the piston the rod can be pushed up
through the block and removed from the top of the engine
Now you should be left with the engine block with the flywheel, fan and crankshaft still fitted.
Unbolt the flywheel nut that we had previously loosened and remove the fan. Now wind the bolt
back onto the crankshaft until the shaft end is just below the bolt head surface.
There are now two methods of removing the flywheel. The first is to use a set of pullers on the
flywheel to separate the flywheel from the crankshaft.
The second method (and the more “ham fisted” approach) is to hit the nut head with a hammer
whilst supporting the crank on the clutch side. I recommend using the pullers!
Now that the flywheel has been loosened from the crankshaft you can remove the nut and
remove the two parts. You are now left with the bare engine block containing the governor
mechanism we want to remove.
Disconnect the linkage from the metal arm on top of the engine block. You can now slide this
arm down through the engine block and remove. There is also a washer on the arm (inside the
engine) so make sure you get this out as well.
With the metal arm removed you can now remove the plastic gear from the top left of the engine.
First of all remove the plastic cap in front of the plastic gear with a set of long nose pliers. There
is a thin, flat washer between this plastic cap and plastic gear. Make sure you get this washer so
it doesn't end up loose in your engine.
Grab the plastic gear with a large pair of pliers or vice grips and pull the gear off. Note: the
plastic gear is held on with a small clip ring so it takes a bit of force to pull off the gear. You can
also use a thin flathead screwdriver and a hammer to dislodge or bend the clip ring making it
easier to remove the gear. Make sure you find the metal clip ring and remove it from the motor.
There is another flat washer behind the gear.
Now that the governor mechanism has been removed you need to plug the hole in the top of the
crankcase (if running the Honda Fuel Tank) or fit a Banjo Bolt if running fuel pump and remote
tank. Which tank you are running the procedure is the same.
First of all you need to thread the hole using an M8x1.0mm Tap to cut the threads. You will
probably need to run a 6.5mm drill bit down the hole first of all. In order to stop the swarf
collecting inside the engine, I tend to tape up the crank bearing and also fit a piece of cloth inside
the engine to catch as much swarf as possible.
Once you have the governor rod hole tapped its time to completely wash out the inside of the
engine to remove and swarf from the tapping process. Take your time doing this and make sure
the inside is spotless. It also helps to blow the inside of the engine block out with an air line.
You can then either insert an 8mm bolt into the top hole (using a small amount of gasket sealant)
or fit your banjo bolt if you are intending to run the fuel pump and remote tank system.
Further details on fitting a fuel pump and remote tank system are covered in the article How to Fit
a Remote Tank and Fuel Pump System.
Now its time to start reassembling the engine.
Start by sliding the Crankshaft back into the engine block and fitting the flywheel and fan. Screw
the Flywheel nut on by hand. This will be tightened to the correct torque later.
Now its time to fit the con rod and piston into the engine block. Insert the con rod into the top of
the engine block and fit a piston ring compressor around the piston. Lightly tap the piston into the
block until it is fully seated making sure not to hit the crankshaft with the con rod.
You can now fit the con rod to the crankshaft and replace the con rod cap and tightening the two
retaining bolts to the correct torque (9ft-lbs.).
Next its time to fit the cylinder head on to the engine, ensuring the 4 cylinder head bolts are
torqued to 17ft-lbs.
Now you can insert the piston stop into the spark plug hole and safely tighten the flywheel to 17ftlbs. Once you have done this you can refit the ignition coil, setting the gap between the coil and
the flywheel to 2thou. The fan side cover and pull start can then be fitted.
Now its time to refit the push rods, cam followers and cam. Slide the push rods back in place
making sure they contact the rocker arms correctly. Now slide the cam followers into place and
then slide the camshaft in place. It is important to have the cam and crank shaft gears correctly
aligned. You will see a small dot stamped into each gear. These two dots need to line up when
the two gears mesh together.
After everything is lined up check to make sure the inside of the engine case is clean. Check the
push rods and make sure they are making contact with the rocker arms in the correct location,
that the exhaust valve collet has been re-fitted and that the rocker arms are correctly seated on
top of the valves. Now bolt up the side cover. Use a torque wrench and tighten the bolts in a
criss cross pattern to 17ft-lbs.
With the engine side cover bolted back on, turn the engine over by hand and watch the valves as
they open and close to make sure everything is operating smoothly. Now re-set the valve
clearances. See our Article on How to Change Valve Springs for information on setting valve
clearance.
Refit the fuel tank at this point if you are using the Honda fuel tank.
Refit the rocker cover and spark plug and then refit the throttle arm to the cylinder head. Drill a
small hole in the throttle arm and fit a Throttle Linkage Arm to connect the throttle Arm to the
Carb.
Now you can replace the carb, air cleaner cover, air filter, air filter cover, and exhaust. Finally, fit
a throttle return spring to the Throttle Arm. We re-use the long stiff spring removed from the
governor mechanism.
Now all that’s left to do is fill the engine with oil and fire it up. You should now be able to rev your
engine to around 5800-6000rpm.