Iflyglow

My Feedback: (79)

I have a Zenoah G20 that runs awesome except for the ocasional cough. It is not the ignition or tank, or cooling. Has anyone experienced this problem? You will be flying along, and the engine will cough, like it is going to quit and then it comes back to life. I have redone the tank twice, and the ignition has been upgraded to C & H. It idles at 1,700 for ever, and spins the 16-6 @ 9,150 100 rpm of of peak. The cylinder head temp hovers around 220. I am running a three line 10 oz Dubro tank, with neoprene fuel line from Hayes, and the clunk funtions very good. I am running a Walbro felt clunk. The carb is clean, and the fuel is 93 octane (no ethanol) mixed 32:1 with Belray H1R. The engine is baffled, and can run a whole tank on the ground wide open with out running over 220 degrees F. The problem allways seams like it happens during level flight or while banking. The ruglator vent has been routed to the fuse. I am stuck as to what will cause this. The low speed is leaned to the point that is does not burble, and I do not think it can be leaned really anymore. It acts like it momentaraly is flooding while otherwise running normal. I have a Zoar 17-6 on the way thinking that the 16-6 is unloading to much in the air and not putting enough load on the engine. O I forgot, the plug looks very good, and is gapped at .020. The engine has 1-1/2 gallons through it, and starts on the 3 or 4 th flip of the prop when cold, and 1st or 2nd when hot. This is the first engine that has ever puzzled me like this ever. The only thing that I can think of is that since this engine is so economical on gas (1/2 oz a min.) that it sucks in a drop of gas that hangs up in the velocity stack, which is enough to momentaraly flood it once in a while. Also the carb insulator block has been replaced with all gaskets and torqued to 30 oz/in per Zenoah.
I can post some pics, if that would help any of you Zenoah lovers out there.

captinjohn

Most engines that coughs is a sign of a lean fuel mixture. Maybe it is tuned that way to keep the mid-range burble out. It may not be better on fuel after you richen it...but if it gets the cough out, that may be better. A tad rich is better than a tad lean. Capt,n

Iflyglow

My Feedback: (79)

Captan,
If I ritchen it at all, it will burble and fourstroke. I am not that lean. You can run a tank on the ground wide open, midrange, idleing etc, and it runs awesome, but it in the air and all will be and then errrrrrrr up errrrrrrr. I am hoping that loading it up with a little more prop will fix. Maybe a little more load will make the little bugger burn the fuel better. It is allmost like it is overspeeding (unloading to much). Genoah rates the HP and torque around 8,500, but then suggest 14-6 to 16-6 props, with the largest turing easily over the peak torque rpms. I am hoping to run it in the low 8's on the ground.

WRK

My Feedback: (2)

Does it do it more often if you go up high (running at the same throttle opening as when it coughs flying level ) and slowly lose altitude over a period of time? If so then you are hearing a once in a while 4 stroke which should not cause the engine to die, slowly losing altitude takes the some of the load off the engine and should make this condition more obvious if that is what is happening.

Iflyglow

My Feedback: (79)

It does not happen when climbing. It useally only happens flying flat and level, or in a banking turn. The only thing I have not checked is the magnet to sensor spacing (air gap). The bracket is machined from C & h, and I have it pressed as far forward as I could get it. It is timed @ 30 degrees's per C & H. I am thinking that the clearance is about .015-.020 now. Maybe I will have to take the bracket off, and file the slots, so I can tighten up the air gap a little. Could it also be that the engine is unloading above the operating speed of the ignition, since it is spinning over 9,000 on the ground, and must certanly unload to allmost 10,000 or more in the air.

jerdavis

My Feedback: (3)

MOTORMAN,
Do you have a kill switch, remote and/or manual? If so maybe the inflight engine vibration is causing switch bounce.

I have a mag kill switch that employs a relay. If not properly insulated (wrapped in foam), it will cause engine misfire in certain attitudes. The misfire never happens on the ground.

Jerry

Iflyglow

My Feedback: (79)

I do not have a kill switch, other than the JR Heavy duty switch that just kills the battery power. I have swapped it for another, but that did not fix it. The only thing that I have done is ruled out radio glitchs. It range checks at 200' with the antenna down, and the engine running at all different rpm's. I am running JR PCM. The antenna is routed in the fuse in the stock location tube, but the plane has metal pushrods, and cable pull pull in the same vacinity. If I was getting hit with PCM, the throttle would be the first to be affected I think. Every servo has a RF choke coil per the instructions. The closest thing to any ignition related item is the throttle servo @ 7" from the ignition battery. I am going to reroute the antenna, and move the battery tonight, and hopefully fly tomorrow. I do not think this is the problem, because the plane still feels rock solid when the engine acts up, and it only seams to do it a couple times in a flight.
My normal engines are a YS 1.40 and two YS 1.10's. I have never had a problem with these types of engines. I put this plane together for a cheap change of pace to fly at big bird events. The fuel cost are awesome compared to my $25.00 a day for YS food.[X(]

octanehuffer

Move the antenna to the outside of the plane and dont change anything else. Did it go away.
I recently had this problem on my plane. PCM. Failsafe was set to idle. I would get a glitch after a hardcore 3D manuver, and it would recover. I have hundreds of flights on it since last year and two weeks ago it started. Not since moving the antenna.

Propwash-don

My Feedback: (37)

Hi! Motorman,
This is Propwash-Don, you horse traded me for my (now your) YS 110. This doen't help you with your guestion, but how do you like the power of the G-20. I was thinking about putting one in a World Models (70 in.) P-47, would it have enough power?

Don

Iflyglow

My Feedback: (79)

Don,
It has alot of power actually. The bad thing is, the stock ignition draws 3 amps. A 2400 mah sub C pack will last one hour. C & H makes an awesome plug and play ignition that draws 300-400 mah. The bad thing is, you have to buy a $299 engine, and then put a $100 dollar ignition on it to make it a viable powerplant for small planes. The C & H ignition is a few ounces lighter, but the big plus is that you lose about 5-6 ounces of battery.
I know you do not like used engines, but I recommend you buy a used G20, and throw the stock ignition and replace it with C & H's. You will then have an awesome engine for the P-47.
Mine turns the Apc 16-6 @ 9,100+ which is allmost identical to a healthy Saito 1.25 if not more. And it does it @ 3.75 a gallon. You also save weight by reducing the fuel tank from a glow size of 16-20 oz's for a 1.20 four stroke to 8 oz for the G20 which will run 15-20 minutes on 8 oz.[sm=wink_smile.gif]

karolh

Reading the Toni Clarke manual on his Titan ZG20 which is the same as our G20, he suggests that the engine can unload as much as 2,000+ rpm so it's quite possible that your engine could be turning in excess of 11,000 rpm which could be causing a misfire if it is too lean. Try richening the mixture to run 200 rpm below max rpm and see it helps.

Karol

captinjohn

Just for kicks...try a prop that loads the engine more...too cut down RPM. Kinda like a chainsaw when you get into the cut more. Top RPM does not always give the best performance! Best Regards Capt,n

Iflyglow

My Feedback: (79)

The problem gets worse (happens more often) if you richen it. Been there and done that. Here are some pics of the radio compartment. The throttle servo is 5-1/2" from ignition battery. I am wondering if this is the problem. The ignition battery is under the little hatch. I will be moving it up under the dash tonight as I wait for the Zoar 17-6 to get here. The closet thing to the front radio wise is the throttle servo. The ignition, switch and ignition battery (under cover) are in the picture.

All the radio equipment is behind the rear seat. Could I be getting a glitch which is affecting the throttle servo (hidden from being worse by the pcm modulation of the JR Radio.

octanehuffer

I have one of my throttle servos 2" away from the ignition. I use a nyrod link between the two though. My electronics are well away from the engine too. I was told that it was to be an internal problem from the plane. Not a hit. Ie, loose or rattling tailwheel, cannister touching the header, ignition wire touching metal, Rx antenna run along side pull pull, etc. My setup has worked for the past 2 years flawlessly until two weeks ago. The odd thing is, that around that time, my tailwheel and axle fell off the plane after dragging the tail along the field in a harrier. I was hovering at the time and saw the two seperate the plane, found them, and reinstalled right at the field. Up until last week, my antenna was routed to just above the tailwheel in the fuse.

karolh

I think that's a good idea to increase the prop load, as I have found that using a Xoar 16x8 gives the best all around performance on mine. What brand and style muffler are you using.

Karol

Iflyglow

My Feedback: (79)

The muffler is stock.

arobatx

My goodness....sounds like you are doing alright with the OEM muffler [:-] I bet it likes the Xoar 17x6 better.

AA5BY

I've two G-20s and one of the birds suffers something like you describe but not exactly similar. Mine will cough only one time shortly into a flight almost always on the first flight of the day and only occasionally on later flights.

If I do a roll shortly after takeoff or on the first downwind, it usually manifest itself then. If I don't do an early roll, it shows up later in some aerobatic maneuver. I only get one blurp and the motor never dies.

My guess is that it is an air bubble that is clearing the carb and gets released from some pocket when the plane rolls or does an aerobatic move. My other plane has the carb mounted 180 degrees different, which may be why it doesn't manifest the problem. If I recall correctly, the cough happens on the one that has the choke on the top. Both motors are mounted inverted.

Iflyglow

My Feedback: (79)

I moved the antenna and the problem went away. It was the trottle going going into momentary fail safe. The engine runs awesome now, spinning a Zoar 17-6 at 8,300.

karolh

Good for you MM37.... the G20 is a real awesome little pocket rocket.

Karol

octanehuffer

We have had our differences, but I always try and help those who need it. Regardless.
Glad it worked out for you.

mrbigg

My Feedback: (21)

awww...........[sm=red_smile.gif]

octanehuffer

LOL
Who wants a ride in my cuddle bunker?

mrbigg

My Feedback: (21)

[sm=lol.gif]

vita-40

I have read all about you,re problem with special interest.I have an evolution g26 and never fixed the problem.I sent it back to hanger9 twice.Thay said it was fine but it still had that scarey blurb now and then.Our field is sourounded by trees ,so a dead stick is usually a dead airplane.I put it in a box and put it away for another day. I don't need the agravation.If you know anybody who needs an all-most new evo 26 let me know.