Newbie to Gas General Information
This thread is here as a FAQ or Starters Guide for newbies to gasoline powered engines. Please do not post regular chit-chat in this thread. It will be deleted.
Consider this a READ ONLY thread.
Thanks,
Rcpilot 04-16-09
There are so many threads with hundreds of the same questions and answers...maybe a few basic things in this thread would qualify as a "sticky" and RCU would help us who provide those answers to reduce duplications.
So... as a "newbie" to Gas. Some things in general that you must keep in Mind and Learn About Doing.
1. All tank and plumbing accessories must be "gas" rated. Dubro brown color stoppers are the "standard". Yellow Tygon is widely used. Clear tubing is crap. All fittings need to be "secured" over their attachment barbs. All smooth brass tubing needs some kind of bump, solder blob, or barb to keep Tygon on, as it swells in use. BEFORE it gets rigid and brittle with age. NORMAL.
1a. Klunks and filters.....gotta have 'em someplace. Klunks in the tanks that are like the little Walbro "felt clunks" in your weedeater work REALLY well. So do more exotic ceramic particle filters. Gotta have a klunk. Gas should be filtered in the jug, too, before it gets INTO your airplane. And yes, tanks only need two lines.... vent to atmosphere and line to carb. You can use a tee with a fuel dot to fill and drain the tank. It will work forever. You also can use three lines, but that gets a little more complicated. Use filters.
USE FILTERS.
1b. Pulse Lines - MANY gassers have a piece of tygon fuel line running from a fitting on the crankcase or intake adapter to an inlet pipe on one of the "sides" of the carb. This line is NOT for gas. It must not be kinked. It cannot have holes. If not hooked to the pulse line on the carb, the carb will not pump. Ever. When in doubt, call the manufacturer. Most of them ship their engines with the pulse lines already properly connected. Sometimes they even have manuals with pictures in them that MAY show this line and it's fittings.
2. Every engine with a Walbro or "clone" carb MUST HAVE it's Low and HIGH speed needles re-adjusted from factory settings to get GOOD performance. EVERY ENGINE!!!
2a. Walbro carbs (and other similar) have PUMPS. Rocking the prop back and forth or flipping it with fuel will PUMP the head full. Spark doesn't work under fluid. The tank can be a long way from the carb, and it's okay. As you rock the prop, watch the air bubble/fuel move up the line. If the bubble isn't moving....the pump isn't pumping. Get the pump wet inside somehow. Fact.
3. Breaking an engine in on the ground is generally not a real good idea. Use the manufacturer's recommended oil ratio for starters, get a couple tanks (or less) through the engine to make sure everything is okay, then go fly the damm thing so it will have SOME form of cooling air over it.
4. Spark plug cap fittings usually fit very tightly if they are the "push on" type, and you will have to push HARD. It's normal. If the plug cap isn't on correctly, it will not run right. EVER. And you'll get unreliable starting, running, and radio interference (all not-good things).
5. Prop drilling - if you have a jig, use it. If you don't, use the prop washer as a guide and try to get straight holes. ALWAYS balance a prop before using it.
6. Most carbs will require you to modify the throttle arm to be "user friendly" for our pushrod/ball link setups. Get over it. It's the way it is. Use a short servo arm to attach to the crappy little plate they supply on the throttle butterfly shaft. Use ball links and very rigid pushrod setups with GOOD servos.
7. Remove and toss the "stop screw" on the throttle arm plate, then unhook the little spring that pulls the butterfly closed, unless you want your throttle servo under constant load/tension. DO NOT REMOVE THE SPRING.
8. Electronic ignitions work wonderfully, if they are getting power. Use a reliable battery with the voltage rating and milliamp hour rating that the manufacturer recommends. WHY??? Because if you toast the ignition from incorrect battery usage - YOU WILL BUY THE REPLACEMENT. If they say nothing, go with a 4 cell 1100mah NiCad, or NimH, or a 5 cell system on a GOOD regulator. Not recommended for newbies. Get some experience with this area. Always use a switch, and setup throttle so you can kill it.
Generally speaking, there are "good" ignitions, and there are "cheap" ignitions, but not so much "Good and Cheap". Ya gets what ya pays for on this one!!!!
8a. Ignitions all have three chunks of wire. ONE, the spark plug lead, also contains the "ground", and must make contact with the outside of the plug hex (where your socket wrench grabs the plug). It can't have holes, or cracks, and should always be prevented from rubbing on ANYTHING. TWO - "Power", usually a "female" battery-type connector with a red and black or red and white wire/connector. This is where the "OUT" of your switch provides power to the ignition. NEVER get the red and other color mixed up ever!!! THREE - the "sensor pickup" - usually a black/white/red (or similar) wire that connects to the thing that is mounted up near the prop hub (on most engines). This is the "hall switch", and picks up the rotation of the prop hub by sensing a magnet when it rotates past the face of this switch. ALL three wires have to connect, and the polarity of these three wires can never be wrong, either. The igniton senses the magnet rotating past the switch on the hub/crankcase to figure out when to send the spark to the plug. It only "knows" when the magnet has passed it. ALL of these work the same way. Rotating the hub magnet past the hall sensor/switch means that the IGNITION **WILL FIRE THE PLUG** if it has power. Many people with injured fingers thought an igniton was OFF when it wasn't and found out by casual flicking of a "hot" prop. The ED department visit usually costs more than an engine. AVOID this, always. Treat a gasser with an ignition attached as if it is HOT, 100% of the time.
9. In general, a new carb will not pump if it has been dry for awhile. Period. Get some gas into the thing by normal "priming", close the choke, flip through a few times, ignition on, throttle at high idle. Engine pops starts, dies, open choke, flip till starts. RESTRAIN you AIRPLANE while doing this. ALWAYS.
10. These gassers need GAS. Not some other kind of make-believe fuel. If yours has ethanol, it will be okay. 95% of our engines will do just fine on regular unleaded 87 octane pump stuff. They also have to have OIL. Nearly all of these need about 30 or 32:1 ratios for their first starts. That's 4 oz to a gallon. Easy to remember. Won't hurt the engine. Use a good oil for 2 strokes. If in doubt, call the ENGINE seller about ratios and types. If they don't answer, THEN post on here.