by Dragon Racing Fuels

In this segment of fuel facts we are going to focus more on the correct fuel and what to look for in a fuel for all you two stroke riders. With a good fuel and proper tuning you will have your 2 stroke at the front of the pack.

Running very high-energy fuels that produce really good power has been one of the key ingredients to matching a two-stroke overall powerband to that of the four-stroke. The components in exotic racing fuels that produce good power and have a lot of energy do not have very good octane. Octane, as we talked about in the first segment of fuel facts, is the rating of a fuel’s ability to resist detonation and/or pre-ignition, is critical in the performance of a 2 stroke motor. The infamous “lead” component is the best octane improver on the market, from a cost and benefit standpoint. With lead you can use
the higher energy components, maintaining overall good combination. From a motor’s standpoint, leaded fuel doesn’t detonate as easily as unleaded fuel, so you’re able to use a higher-compression motor setting. When more compression is run, the
bike has greater acceleration.

The two-stroke engine completes the thermodynamic cycle in two movements of the piston (rather than the four of the familiar four-stroke). This increased efficiency is accomplished by using the beginning of the compression stroke and the end of the combustion stroke to simultaneously perform the intake and exhaust functions. In
this way two-stroke engines often provide strikingly high specific power.

When selecting a fuel for your two stroke you need to make sure that the fuel is not to light. When I say light I am talking about the specific gravity of the fuel. Once you start getting down around the .710 range the pre mix oil will not want to stay suspended. Most two stroke fuels are in the .715 range and heavier.  You also need to take into consideration the octane rating, two strokes stand to benefit from higher octane more so than 4 strokes. You need to find a fuel that meets the octane level necessary for you application and you should look for a fuel that has a high energy value.

A two stroke engine is not difficult to tune. As with a four stroke engine you should first check your carburetors. First let the vehicle warm up and while sitting at idle slowly twist the throttle increasing the rpm’s. Come back to idle and repeat the process a little faster each time. If you are having problems with your carbs it should eventually act up. Sometimes you have to operate it and try accelerating to put some load on the vehicle. Eventually it should become unresponsive with a slow flat “buuuwwwaaa” sound and then take off. This would be a caused by a lean condition and needs more fuel. If the vehicle stumbles, burbles and stutters when you gas the throttle it is rich and needs less fuel. Always be careful when tuning a two stroke engine to make sure it doesn’t operate in a lean condition or damage can occur to the under lubricated engine. Although this is not the best method for checking carbs, it may help you out. You can also check the spark plug by instantly stopping the motor during the experienced poor running condition. Remove the spark plugs. First check to see that the plug looks the same on the electrode. Also check for an ignition problem if the spark plug is black and fouled showing that it was not firing. Check the coloring on the electrode. If it’s black the mixture is too rich or your plugs are fouled out and may be the problem. If the spark plugs look white or light grey the mixture is lean. The ideal color is a light brown.

The absolute best way to check the mixture is by looking on the top of the piston through the spark plug hole. This will require a light, white L.E.D. penlights work great. Rotate the piston to the bottom of the bore you are looking down. Look on the sides of the piston that are in line with the crankshaft. The top of the piston should be black or tan. The sides of the piston crown should have little “pockets” on them. You will be able to see the shiny aluminum in the pockets. These pockets are caused from cool gas flowing through the transfer ports and across that spot on the piston. The pockets should extend inward about a quarter of an inch and be approx. half an inch wide, depending on bore size. This will be an ideal fuel mixture and is very accurate. The farther the pocket extends inward the richer the fuel mixture is. If the pocket is very small it’s lean. If you see a grey ring about a quarter of the way in from the edge all the way around, be worried. The grey ring (of death) means the mixture is extremely lean and is about to burn a hole in your piston if not corrected. Depending when a hesitation is felt right away or higher rpm’s will matter. Low range is controlled by a pilot or low end jet, located in the bottom of the carb. Carbs that have a throttle slide will have a mid range needle that extends through the center hole of the carb. The high rpm’s are controlled by the main jet. The main jet is located in the bottom center of the carburetor. It will usually be close to the pilot jet but will be twice the size. This is the most important jet because it is used at full power. Be careful to keep this rich enough! Jets are small round brass pieces that are numbered. The higher the number the larger the hole, and the more gas it will deliver. Two stroke engines can last a long time if properly tuned, and are not that difficult to work on.

In our next segment of Fuel Fact we will discuss the proper fuel for 4 strokes and talk to someone in the motocross industry that has a good understanding of the new Honda four strokes. Stay tuned to Vurbmoto.com for the next Fuel Fact brought to you from Dragon Racing Fuels. If you have a topic you would like to see on fuel facts please send your request to support@dragonracingfuels.com

Mark Ticen – Dragon Racing Fuels