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Saito FG 30B coughing mid air

Old 09-24-2022, 03:04 PM
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Pfroelicher
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Default Saito FG 30B coughing mid air

Hi all Saito fans
I have many Saito Motors.. just bought aFG60R3 which runs really good which makes me happy whenever I start it up. .. but..back to the topic. I have this older FG30B Gas in a Seagull Bücker Jungmann. Great combination.. flies very scale, good and balanced.
It drives my crazy.. Whenever I start it up.. I have to hold the Aircraft 90º Counterclockwise (the engine is mounted upside down) to eliminate this vapour lock that is in the carburetor.. as said in the manual. So far so good.. It idles perfeclty.. takes on throttle great.. everything is perfect. I go up and do some rolls.. all is well.
After some minutes of flight.. I feel,, that doing negative G, for example, or a roll to counterclockwise, or a roll 360.. whenever I come to this position.. the motor coughs ou even stops.
i tried all ajustments, make it leaner, make it richer, fumble with the idlde needle.. check all tubing.. check vacuum in tank.. check Ignition cabeling..
BUt.. I think it is something in this WEIBRO Carburetor that is not right.. Somehow it makes this Vapour lock, that is advised in the manual to be taken out, holding the Motor sideways, come back in mid flight..
Does anyone have a hint what I should look into?
Should I change the carburetor?
Yours
PIerre
Old 09-26-2022, 10:45 AM
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ForcesR
 
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Hello Pierre, if the air purging of the metering room is carried out IAW with the procedure outlined in the instruction manual it's highly unlikely that the engine would cough again midflight as you have indicated. I have the FG30, FG36 and FG90R3, after purging the air from the metering room IAW the instruction manual the coughing never ever happens again during flight maneuvers. Do you carry out the purging procedure before every flight? When you do the purging procedure do you go flying right away, or do you stop the engine for whatever reason, then restart the engine and then go flying? I have never had any of my three engines stop in flight due to coughing, I know this as fact because I haven't done the purging procedure on the ground for several years, I do the purging procedure in the air because I found it too awkward to do on the ground.

I'm looking forward to your response to my questions.

Roger
Old 09-26-2022, 12:15 PM
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Pfroelicher
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Hi Roger,
thank you a lot for your answer.
I turn the model sideways 90º Every time I fly before takeoff. This how do you know this room is called Metering room? Is there a Manual for this?
Also. can I check these Membranes? I had once, a long time ago, disassembled the carburetor.. THere is not even a kit for spare parts for this carburetor, that I could buy and see, if something is to be replaced.. only the whole carburetor.
Well.. On the ground.. After turning the Model.. it always coughs and stops.. Then I start it again.. turn it again.. normally it does not stop.. idles nicely. takes on gas nicely.. has nice RPMs.. Go flying.. make a roll after 3 minutes.. and.. jabang.. motor coughs.. make a landing (emergency if motor stopped).. turn the model again on the tarmac.. and it works well.. for some minutes..
With me.. this air bubble in this "metering" room.. must somehow be created during normal use.
I will.. again.. dismantle the entire carburetor.. Would be nice to have some instructions and/or spare parts to see if I can make it work.
Old 09-26-2022, 12:42 PM
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And I found this thread with other people having the same problem.
GAS Saito
Old 09-26-2022, 02:21 PM
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ForcesR
 
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Pierre, when you begin the air purge on the ground do this procedure. Run the engine at high idle for approximately 2 minutes then go full throttle then turn the airplane 90 degrees left wing down and run the engine at full throttle for 20 seconds. Then return the airplane to normal level orientation and return throttle to idle. The carburetor metering room is now purged of air, and you can launch the airplane for a cough free flight. You don't have to do the air purge before every flight, it only needs to be done one time before the first flight of the day unless you are stopping the engine after flying by fully closing the throttle to cut off the fuel supply. If you're always stopping the engine after flying by fully closing the throttle then the air purge has to be done again before each flight. Stop the engine by turning the ignition switch to off, then you will not have to do the air purge before the next flight or subsequent flights.

I believe it's your current technique in doing the air purge, not a fault with the carburetor.

Just for your info there is a carburetor gasket/diaphragm repair kit available through any small engine repair shop for the Walbro type of carburetor used on the Saito FG30, FG36, FG40, FG57T, FG84R3, FG90R3. It's Walbro carburetor repair kit # K10-WYD. https://www.worthpoint.com/worthoped...k10-1786275719


Roger

Last edited by ForcesR; 09-26-2022 at 04:13 PM.
Old 10-29-2022, 06:04 PM
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Soo.. I bought this KIT.. even being here in Brasil..Amazon shipped it in 20 days from California...
Exchanged all gaskets and membranes.. Started the engine.. sounded fine.. turned it 90º.. it stopped.. started again.. flew some minutes.. it was a bit better.. But after a while.. doing "dives" I could make the motor cough.. nearly die on my.
So I dissasembled again and this time bent the lever, that activates the Needle, that controls the flux into the metering room. so.. that suposedly there is more fuel in this room.. And.. all was well.. Flew two flights with no coughing and was the happiest person.. But then.. the problem came back????
I do not know what to do.. I will redo the whole fuel pipeing.. although I cannot image that there is something faulty. Might even buy a whole new carburetor.
I dissasembled it all.. the only thing I did not check or take out is this starformed valve...that is in the metering room.. What's that for.. That might be faulty.. Can one exchange/check that?
Old 10-30-2022, 11:07 AM
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ForcesR
 
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Originally Posted by Pfroelicher View Post
Soo.. I bought this KIT.. even being here in Brasil..Amazon shipped it in 20 days from California...
Exchanged all gaskets and membranes.. Started the engine.. sounded fine.. turned it 90º.. it stopped.. started again.. flew some minutes.. it was a bit better.. But after a while.. doing "dives" I could make the motor cough.. nearly die on my.
So I dissasembled again and this time bent the lever, that activates the Needle, that controls the flux into the metering room. so.. that suposedly there is more fuel in this room.. And.. all was well.. Flew two flights with no coughing and was the happiest person.. But then.. the problem came back????
I do not know what to do.. I will redo the whole fuel pipeing.. although I cannot image that there is something faulty. Might even buy a whole new carburetor.
I dissasembled it all.. the only thing I did not check or take out is this starformed valve...that is in the metering room.. What's that for.. That might be faulty.. Can one exchange/check that?
After replacing the gaskets and membranes what did you do after the engine stopped during the air purge and you started the engine again? Did you directly proceed to flying the plane, or did you turn the airplane to 90 degrees again and continue with the air purge at full throttle for 20 seconds then returned the throttle to high idle, then you flew the plane?
Old 10-30-2022, 12:11 PM
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I turned the airplane again.. this time no reaction.. and flew.. at many times I had the airplane turned and full throttle for 20'.. ... but in the air.. the phenomena came back.

I consider buying a new carburetor..
Old 10-30-2022, 01:11 PM
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ForcesR
 
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That's very puzzling, the cough should never have happened again after doing the air purge as you have described...! I concur with your plan to purchase a new carburetor. Please repost the results after you purge the air and fly the plane with the new carburetor installed.
Good luck!

Roger.

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