Performance Basics

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 your engine.
REMOVE THE GOVERNOR: When upgrading your engine, the first modification we recommend is removing the governor. The governor limits RPM to 3600. When the governor is removed, RPM will increase to about 5200. The extra RPM provides a dramatic increase in performance. Cost: FREE
UPGRADING VALVE SPRINGS: After the governor is removed, the stock valve springs will begin to float and limit your rpm to about 5200. Installing stiffer valve springs will allow the engine to spin more than 5200 rpm. We installed 18LB Valve Springs and it was a very simple upgrade allowing us to spin our engine up to 6500 rpm. Cost: $8.00
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 fairly inexpensive. Cost: as low as $28.00
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.
RE-JET CARBURETOR: 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 jets 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 emulsion tube for more low end power. Cost: $15.00
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. Each indexing washer 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. Cost: $6.00
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". Cost: FREE
REDUCE DRAG:  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. Cost: FREE
ADVANCE TIMING: Advance your ignition timing by filing the stock timing key. Every 0.006" you file off of the timing key is equal to 1 degree advance. Removing 0.048" would be equal to an 8 degree timing key. Cost: FREE
ALUMINUM FLYWHEEL: 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 aluminum flywheel (This link goes to our camshaft install article however the beginning shows the removal of the flywheel and the end shows installation of the flywheel) 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. Cost: $105.00
INCREASE COMPRESSION: For those of you using the popular Honda GX200 a great hop up trick is to install a GX160 (18cc) cylinder head or one of the older 14cc cylinder heads. These cylinder heads have a smaller combustion chamber which will increase compression. This is a simple bolt-on trick which provides impressive gains in horsepower. Cost: $46.00
PORTING: 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. Cost: FREE
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. We use 14 oz. of oil in engines that still have the low oil sensor and 16 oz. of oil when the low oil sensor has been removed.