TideLog Archive for February, 2012

I’m an avid fan of nitro remote control car racing, and regularly repair cars for people as well as building them and servicing the engines. It’s a fact of nitro life: sooner or later, your engine won’t want to start or stay running long enough for you to get up on the drivers’ stand. Don’t shelve your engine and start charging batteries just yet; hard-starting issues aren’t usually tough to fix. Follow these steps, and you’ll reach nitro heaven again in less time it takes you to say spark plug!

Got pinch?
Before we start troubleshooting, let’s first make sure the piston and sleeve aren’t toast. Remove the engine’s glow plug, and rotate the flywheel with your finger. As the piston reaches top dead center, you should at least feel resistance as the piston is “pinched” by the sleeve. This tight fit seals the combustion chamber and is critical to engine performance. If you don’t feel any pinch, you probably need to replace your piston and sleeve.

Check out the glow system
Even rank novices know to check out the glow plug when starting problems occur, but few remember to check the other half of the glow system—glow starter! Make sure that your glow starter is fully charged (or has a fresh battery), and its contacts are clean. Press the glow plug into the glow starter and watch the coil; it should almost instantly glow bright orange, and the entire coil should glow. If the coil glows dull red, or it doesn’t glow at all (and you’re certain the glow starter is charged and making good contact), you need a new plug.

If you have an electric starting system, the testing procedure is the same, but you must remember to touch the glow plug to the heat-sink head as you crank the engine; if you don’t, the glow plug won’t light because the circuit is incomplete.

Make sure that the engine’s heat-sink head and backplate screws are fully tightened. Cinch them down in the pattern shown to ensure even tightness; if you torque the screws down completely one at a time, you’ll warp the parts and prevent them from sealing properly against the engine. Pull-start engines require the starter housing to be removed for backplate access; be careful not to uncoil the starter spring in the process! Slip a screwdriver between the backplate and housing to prevent the spring from popping out, then tape or rubber-band the assembly after removal so it doesn’t go “boing!” on your bench.

Speaking of sealing…
While you’re wrenching, take a look at the gaskets or O-rings that seal the carburetor base and backplate. If they’re damaged, replace them. A coat of Permatex Ultra Copper sealant (or similar sensor-safe automotive sealant) is also good insurance against air leaks.

Know your limits
If your engine seems to start easily enough but stalls as soon as you let off the gas, check your idle-limit screw—the little guy just in front of the carburetor opening. Turn the screw so the carb still has a 1mm (or so) opening when full brake is applied. If the screw turns very easily, put a drop of thread-glue on it to prevent engine vibration from causing the setting to drift. After putting thread glue on the screw, then screwing it back in, quickly adjusting it back to the correct position, leave the screw for 30 mins to let the thread glue harden.

It’s best not to do this just before a race as the glue needs time to harden, do it the night before!

Needle needs
If you went nuts with your carb’s needle settings before your starting troubles began, you should reset them to factory specs. Lost your manual? For most engines, a good starting setup is “flush” for the low-end needle (adjust the needle so its screw head is level with the opening in the carb body the screw head sits in), and “two turns out” for the high-end needle (gently turn the needle clockwise until it bottoms out, then give it two full counterclockwise turns).

How’s that fuel tubing?
Even tiny pinhole leaks in your vehicle’s fuel and pressure lines can cause erratic engine operation and starting difficulties. When in doubt, replace the fuel tubing; it’s inexpensive, and with all the color options available, it’s a cheap and easy way to give the chassis a new look.

Tanks for the memories
Your fuel tank isn’t clogged, is it? Look for any crud in the tank where the fuel pickup line is, and get it out of there. Likewise, you should check your vehicle’s in-line fuel filter (if so equipped) frequently; it can become clogged with debris and impede fuel flow if not cleaned regularly. Finally, consider removing the tank’s plunger-type primer, if so equipped; such primers are prone to air leaks. After you’ve removed the primer, fill the hole with a machine-thread screw and some silicone sealant.

Freshen up your fuel
If your jug of fuel spent the winter on the garage floor, it has probably gone bad. Very bad. Dispose of it responsibly, and get yourself a new gallon. Store it in a cool, dry place away from sunlight and off the floor. If you like to race outside or go on extended-play missions outdoors, try to keep your fuel out of the sun and heat. Trinity’s Nitro Kooler bags are the best way to prevent solar heating and protect fuel in clear containers from light exposure.

Now that you’ve ironed out any potential problems, you’re ready for a first-pull startup. Here’s how to make it happen:

1. Prime the carburetor. Remove the pressure line from the exhaust pipe, and blow into it; you’ll see a solid jet of fuel fill the fuel line up to the carburetor. When the fuel hits the carb, stop blowing. Reinstall the pressure line.

2. Install the glow igniter. If it’s a cam-lock type, make sure it’s secure. Is there a gauge on top? Make sure the needle is in the green.

3. Crack the throttle. Instead of triggering the radio, just turn the throttle-trim knob to open the carb another 1/2 millimeter or so.

4. Pull the starter cord! Give a sharp tug, and your engine should now be running. At the very least, it should pop on the first pull and start on the second or third (the extra tugs are usually only required if the carb wasn’t fully primed).

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