Products - Frequently Asked Questions (FAQ)

When an engine only runs for a few minutes and then quits, it can be one of the most baffling problems for a modeler to solve. Resetting the needles, changing glow plugs, trying different fuel, even replacing the fuel tank and its plumbing doesn't work. The engine still runs only a few minutes and quits. For an airplane flyer, this means dead-stick landings and possible airplane damage, and it costs races for the car guys.

What causes this?

Basically, the cause is engine overheating. Because the engine runs normally for a while before it quits, the overheating is gradual. You can have good fuel and a good needle setting, but still have the problem.

Gradual overheating is most commonly caused by the exhaust system. If the exhaust system is slightly restrictive, the engine won't be able to 'breathe' freely, and it will retain a little bit of heat each time it fire. Eventually, the heat will build up to the point where the engine quits. Restrictive exhaust systems are usually the result of using mufflers, pipes, and headers that are not provided by the engine manufacturer, but are made by third-party manufacturers.

Another source of gradual overheating is an exhaust system that will not allow enough pressure to be developed so that the engine will have good fuel flow. In order to solve the exhaust restriction problem, the muffler system becomes so free-flowing that too little pressure is developed to pressurize the fuel tank enough.

Mufflers and exhaust systems are usually made in only a few sizes, and then adapted to fit a wide variety of engines. For example, one popular manufacturer makes a "Pitts" style muffler for a wide variety of engines. The main muffler body and exhaust pipes are the same, but the portion that attaches to the engine's exhaust port is different, depending upon the engine it's to be mounted to. It works very well for .61-size engines, but is a bit restrictive for .91-size engines. The .91-size engines will tend to gradually overheat and quit.

Here's a checklist to help troubleshoot the engine problem:

Is there a sufficient amount of fuel?
If there is only a little remaining fuel left in the tank, the tank will soon be empty. The 4-stroke engine has good fuel efficiency and the running time is slightly longer. However, the fuel efficiency of the 2-stroke engine is not good. Always try to keep the tank filled with fuel.

Is a compatible plug used?
It is essential to use a plug that is recommended in the manuals. If a plug having an extremely different temperature range is used, problems such as sudden stopping of the engine as soon as the throttle is operated, erratic idling, or premature plug wear may result.

Is there any danger of overheating?
If the needle valve is closed too much for a lean mixture, the cooling effect by the fuel drops and the engine overheats. In the worst case, the cylinder will seize. Therefore, the needle should be carefully set.

Are there any loose or cracked engine parts?
Is the engine head or carburetor fixing screw loose so as to cause compression leaks or suction leaks? Perform proper tightening while taking care to prevent uneven and inadequate tightening. Furthermore, at the same time, check to see that no parts are damaged.

Is the fuel tank properly secured?
If the fuel tank resonates with the vibrations and the fuel foams abnormally, the engine may stop on rare occasions. This is caused by a large amount of air being mixed in the fuel transfer tube. The fuel tank should be securely attached.

Does the engine stop immediately after being started?
Once started, let the engine run until the rpm stabilizes without turning off the plug heat. When first starting a cold engine, the engine sometimes suddenly stops as soon as the electricity is turned off.

Does the fuel pass normally through the fuel tube?
Clogging of the fuel system will hinder stable engine speed. It is important to periodically clean the fuel lines. If the fuel system becomes clogged when the needle valve is set lean for high rpm engines, there is a danger of overheating.