In this section we cover several modifications you can
perform on your engine for little or no cost. Don't let your limited
budget interfere with your desire to go faster. We offer these
suggestions with the beginner in mind.
The following modifications were performed on our 6.5hp
Honda GX200 with great results. The hop up parts and performance
information on this page will work on your GX160, GX200, Blue OHV clone
engine as well as other karting engines. If you are racing or just out
to have fun, these basics are a great way to start opening the potential of
REMOVE THE GOVENOR:
When upgrading your engine, the first modification we recommend
is removing the governor. The govenor limits RPM to 3600.
When the govenor is removed, RPM will increase to about 5200.
The extra RPM provides a dramatic increase in performance.
After the govenor is removed, the stock
valve springs will not be able to handle the increase in RPM.
Installing stiffer valve springs will prevent the valves from floating.
We installed 18LB
and it was a very simple upgrade.
HIGH FLOW EXHAUST:
The stock exhaust is
very restrictive. After seeing the inside of a stock muffler,
we were surprised our 6.5hp Honda could even run with the stock exhaust.
Upgrading to a high flow header
is a big performance enhancement. This is a simple upgrade and
HIGH FLOW AIR FILTER:
The stock air filter
is also very restrictive. Upgrading to a high
flow air filter
will net another increase in power. Honda
or clone, 6.5hp or 13hp, these engines like to breathe.
With the increased air flow from the header and high flow air
filter, it's time to add more fuel to the combination. After
trying a few different main
and checking spark plug readings, we ended up with a #90
main jet. Cost: $6.00
The stock carburetor
can also be upgraded with a GX140
for more low end power.
INDEX THE SPARK PLUG:
This is an old trick that hot rodders have been doing for years.
Indexing the spark plug will help clear the combustion chamber of
unwanted gases. The goal is to have the open end of the electrode
facing the exhaust valve after the spark plug has been tightened.
will change the position of the electrode by 1/4 turn enabling
you to achieve the desired position of the electrode when the spark
plug is installed. This upgrade may not provide the same "seat
of the pants" increase in power as the above recommendations,
but every little bit counts.
ADJUST SPARK PLUG GAP:
The larger the gap, the bigger the spark, the more efficiently
you burn the air/fuel mixture in the combustion chamber. If
the gap is too big the spark will not jump the gap. Increase
the gap in small increments until you find the right setting.
We ended up setting our spark plug gap at 0.045".
Behind the recoil starter is a plastic fan that helps cool the engine.
Cutting every other blade off of this fan will reduce drag and help free up
some power. This task can be accomplished with a good set of shears or
a hacksaw blade in about 15 minutes.
Advance your ignition timing by filing the stock
timing key. Every 0.006" you file off of the timing
is equal to 1 degree advance. Removing 0.048" would
be equal to an 8 degree timing key.
Stock flywheels, especially on clone motors,
can come apart at high RPM. When a flywheel lets go at high
RPM, it's similar to a grenade going off. Needless to say this
is a very dangerous situation which can be lethal. Install an
to prevent this disaster from striking you. With
the reduction in weight you will get increased horse power and a quicker
revving motor. This is an expensive part, but it's good insurance.
For those of you
using the popular Honda GX200 a great hop up trick is to install a
GX160 cylinder head. The GX160 cylinder
has a smaller combustion chamber which will increase compression.
This is a simple bolt-on trick which provides impressive gains in
Every great go kart racing engine
needs a ported cylinder head. Porting isn't recommended for the
beginner, however, we all have to start somewhere. Port work can be
accomplished with some simple tools and a lot of patience. Start with
mild port work by smoothing out any rough edges and factory imperfections.
To learn more about porting you can visit
DIY Porting Guide.
CHECK GASKET ALIGNMENT: While working on a
clone engine we found an intake gasket had been installed backwards from the
factory, constricting the flow of fuel. When installed correctly, the
gaskets do not fit perfectly and can be trimmed with a razor blade to be
sure they do not block any passage ways. Every little bit counts.
We even file down the back side of the bolt that holds the throttle blade in
the carburetor so it does not interfere with the flow of fuel.
OIL: Use a good quality,
synthetic motor oil. We use 10w-30 Mobil 1 and we change it very frequently.
I can't stress enough the importance of frequent oil changes with a good
oil. When using a 15 degree engine mount with your GX160/GX200, use
13 to 14 ounces of oil.