cwharper

Hello,

I've got a G-20 brand new never been run and never seen gas. So I mounted it in a plane, fueled up the tank, turned on the 4.8v battery to the ignition and started flipping. Nothing happens, not even one hiccup. I even tried an electric starter that turned it over mighty fast. What's wrong?

Now to give all the details of what I have done before posting here.

- 4.8v battery fully charged, a professionally made battery from JR 1650mah
- gasoline 32:1 mix with Stihl brand 2-cycle oil
- spark plug has a blue spark, visible in daylight, occurs when magnet passes sensor
- after initial tests were unsuccessful I reset the needles to what the manual said were default positions
- tried turning needles while electric starter turned engine
- tried various throttle positions, full, idle, middle
- took carb off and disassembled, it had gas in it, all diaphrams were functional, nothing was sticking, needle valve was funtional and not stuck
- found out about port pressure holes, so made sure they were lined up without obstruction
- I probably checked the spark about 7 or 8 times just to be sure.
- I see that the carb is drawing gas into it from the fuel line
- after using electric starter I can smell gas

I'm new to gas engines on model airplanes, but I'm not new to 2-cycle engines in general. I have three chainsaws of various sizes of which I have disassembled their carbs and replaced diaphragms, troubleshooted problems, and tuned for maximum sawing power.

The electronic ignition is something I'm new to also, my chainsaws all have magnetos. The prop position on the hub is something I'm not sure of, but it shouldn't have mattered when I used the electric starter.

Any help is appreciated.

w8ye

My Feedback: (16)

I don't know about the Zenoa ignition but most brands, if you remove the plug to look at the spark, you have to run a ground wire to the crankcase or the spark will either jump inside the CD unit or across the pickup and take one or the other out.

cwharper

It's got a wire from the module to the crankcase.

w8ye

My Feedback: (16)

Did the spark plug get "WET" with fuel when you were trying to start the engine

rcdude7

My Feedback: (264)

Is the carb "wet" with fuel when you attempt to start? A good wet prime is neede to get the fire started. Is the plug gap roughly .020"?

Did you try cranking the engine with the choke closed until the engine "pops"? Open choke, crank again with throttle at idle or very slightly open, and it should start.

If you have compression, fuel, and ignition, the engine will start. If not, something is missing.

Good luck

cwharper

Did the spark plug get wet? It probably did, but when I had it out checking it, I spun the engine over with the electric starter to clear it out in case it was flooded (ignition off) at the same time drying the plug.

After all the cranking I did and the smell, it's hard to believe the carb is bone dry. The intake sure smells like gas, the exhaust too.

The plug is the one that came with it. I believe the numbers on it were nyk 6 something,

The starting method is how I start my chainsaws, choke on, pull rope a couple of times until it fires, open choke, pull rope one or two more times and it's running. That's what I expected with this Zenoah, but I never did get the pop or initial fire with the choke closed. I even tried some carb cleaner directly into the carb but that didn't produce anything.

Compression (yes), fuel (yes), ignition questionable given the history I've read on the Zenoah G20, but I still get a blue spark, no way to tell what it's doing inside though.

skillet92

I have one of these in my Corsair and it is a great starting motor. I have a Velocity Stack on mine so I put my thumb over the opening and turn the prop about 6-7 times(Throttle all the way open and the ignition OFF) I just turn it slowly to get gas in the barrel and then turn the ignition on (arm away from the prop) Set the throttle alittle above idle and start flipping. By 3 or 4 flips it id purring.

PS carb cleaner is not a good fire starter. Ever wondered why a car that has been cleaned with carb cleaner runs rough until it clears out or if you spray it in to a running cars carb it will cut off!

fjk6807

My Feedback: (1)

Without having your engine here to look at I would guess that you are not getting fuel in the cylinder. first make sure both needle settings are at about 1.5 to 2 turns out from seated. (assuming you have walbro carb.) With ignition off fully open the throttle, choke the engine and then place your thumb over the carb opening and turn the prop in counter clockwise direction until your thumb gets wet with gasoline. This lets you know the carb is full and the engine is drawing fuel. With the throttle still fully open rock the prop back and forth five or six times. This will get the fuel atomized and into the cylinder. Now bring the throttle to idle and turn the ignition on. I prefer to also release the choke at this time as you have already primed the cylinder at this point and the engine should start without requiring the choke. Be sure and wear a thick glove. Start flipping the prop counter clockwise and the engine should fire and run. When hand starting the best prop position is with the prop tips at 1:00 and 7:00 when at the compression point. If you are using an electric starter this will not matter.
If using this procedure does not get you going you have a more severe problem. Possibly timing being way off. If turning the prop continuously in a CCW direction does not get your thumb wet during the priming process then you have a fuel deliver problem. Unlike most weed eaters there is no priming bulb on these engines therefore you have do as stated above. Good Luck

cwharper

Ok, today at the field I borrowed someone's heavy duty starter, mine wasn't turning fast enough. And we managed to get it to run. It didn't really want to start and hand flipping still did nothing. After starting it would only run at half to full throttle, anything less and it quit. The lowest I could get it to idle is 5000 rpm, the highest rpm was about 9300 with a 14x6 prop. Turning the needles made a difference on the high end rich to lean, the low needle didn't make that big a difference except that if it was too far out or too far in it wouldn't start at all, no matter what we did.

There are a couple of gas flyers at the field and after they all had a turn at it, the consensus seemed to be that it didn't have good compression.

When I flip it over by hand it does feel a little mushy going over, but I guess I don't know what to look for. I've always started chainsaws with the rope and never really felt the compression.

So what constitutes good compression?

skillet92

My opinion is that there is something wrong with the motor and not the carb. I had a 2000-2500 idle on first start and it would turn a 15x6 APC better than 9500 to begin with. This is the best running gasser that i have. Now if i remember correctly mine did not have any real compression to begin with. It has since developed a lot as it has run more.

tkg

My Feedback: (1)

Sounds like the one of the carb gaskets is flipped and the pump can't work. Did you remove the throttle spring or make a new throttle arm on the carb???

FlyItLikeUStoleIt

I have the exact same problem. The g20 is mounted on a Seagull Edge and the last time at the field it was running great, as it always has for about a year. Last weekend before I went to the field, for some strange reason, I tried to start it before I left and could not even make the engine pop. Usually the thing is running smooth after about 3 or 4 flips. And as you also said from what I'm seeing the thing should at least pop or something. When I place my thumb over the carb, it gets wet with gas, I can see the spark, and I can feel good compression. This makes no sense at all to me, and I'm almost frustrated.

FlyItLikeUStoleIt

Got it going today, finally!!! Same thing with the electric starter, got it running with a starter and it would only run on the upper end. Anything below 1/4 throttle and it would die. Mine was sucking air at the inline filter between the tank and carb. I replaced the tubing and ran it straight from the tank to the carb just for an experiment, and I had to retune the low end needle. It runs perfect now on the ground, and I can flip start it now. I didn't have time to make it to the field today. I'll keep ya'll posted on the results at the field.

cwharper

I tried mine straight from the filler tank as well, even primed it with the hand pump, same result though. Would only start with the electric starter and would only run at 5000 rpm and above, dies with anything lower. I'm inclined to believe something in the carb is either stopped up or it's getting air somewhere else. But I haven't had time to play with it. My rcgf 20cc is keeping me busy while I break it in and get it ready for maiden tomorrow.

arobatx

Any chance your throttle plate is openning backwards? It is designed to open one way, and pass over the high and low circuits drawing fuel into the venturi. However, many mitakenly set it up to open the wrong way, in an attempt to get throttle linkages lined up better...etc.

RACJ

Sounds like low speed needle or circuit is clogged with trash. Tiny piece of gasket,metal shaving,anything from manufacturing. Bet the high speed needle is set rich to ge it to run 5000 and up as low circuit is contributing nothing. Aerovate thread here has guy with same problem and great pics on carb checks and article on Walbro carb dissassemble and set up. Check it out,lots of info and help. Le me know on this and the rcgf20cc. I ordered one rcgf20 and I'd like to know how yours does.THANKS

karolh

It is always best to have a straight feed line from the tank to the carb, meaning no T for fuelling or inline filters. The more connections you have the greater the possibility of introducing air into your system.

Karol

FlyItLikeUStoleIt

Problem solved. Ran perfect today for 4 flights. Sometimes I overlook the simple things. The problem was the inline filter was loose were it screws together and the engine was sucking air at the filter. I still find it hard to believe that I couldn't even get it to pop when flipping it, but nevertheless it wouldn't. Sorry this wasn't your fix too CWHARPER, maybe someone can learn from it in the future. These forums can be a great help.