ezflyr

My Feedback: (32)

Hi All,

After sitting for two years, I started flying my Hangar 9 1/4 scale Cub again this year. Unfortunately, the Zenoah G20ei that powers this airplane has become progressively more finicky this year, and yesterday I took it home from the field without even flying it! Currently, the engine will not idle, or transition to to higher throttle settings without bogging down and dying. It will start at high throttle settings, and run pretty well at high power, but that's it. I finally reset both needles, and started tuning the engine from scratch, but never made the engine run much better.....

I noticed a couple of things that might offer a clue to the problem. First while fueling the model, I noticed fuel dripping out of the intake velocity stack. I have a two line fuel system (vent, and fill with a 'tee' to the carb) and this has never been a problem before. Secondly, while the engine was running, I noticed a lot of fuel seemed to be streaming out from the vent hole in the carb backplate. After running, the entire carb area seemed to be quite wet with fuel.

I assume all this points to carb trouble? Is it practical to rebuild the carb, or should I just replace it? A fellow member at the field opined that 'ethanol in the fuel corrodes the passages in the carb, and they aren't rebuildable". Has anyone had good luck rebuilding the G20ei carb? If so, where do I get a rebuild kit? Horizon does not show a kit for the G20ei.

Thanks!

John

mogman

If it's been sitting for two years, I would suggest it needs a carb kit/rebuild and clean out. See if you can get a number off the carb,(WT 257)? or take the carb to a saw/small engine/lawnmower shop. They should be able to provide a kit for you. A lot of Walbro carb kits have parts for different models of carb.

It might also be prudent to check/replace your fuel lines etc.

Good luck.

av8tor1977

My Feedback: (6)

It is HIGHLY unlikely that your carb is ruined and/or un-rebuildable. However it does sound like it is time for a rebuild. Get a K10WAT or K20WAT carburetor kit, and rebuild it. The carb rebuild kits are readily available from e-bay or numerous online small engine supply shops. Cost is from 5 to 15 bucks depending on who you get it from. It most likely has a bad regulator diaphram from your symptoms, but a good cleaning is in order anyway. I tried to upload the Walbro Service Manual here for you to peruse, but the file is too large. PM me an e-mail if you would like me to send it.

AV8TOR

karolh

Contrary to what others might tell you, ethanol blended gasoline will not harm your carb's body in any way. The diaphrams might deteriote at bit quicker over time and need to be replaced but that's the worst thing that can or will happen because of ethanol blend fuels.

Karol

speedracerntrixie

My Feedback: (29)

The meetering needle in the carb is stuck and letting fuel just pass through the carb. A carb kit and a good cleaning will solve the issue.

rangerfredbob

My Feedback: (13)

I second the regulator diaphragm being bad, I had the same symptom a month ago on my plane, took the regulator cover off and the diaphragm was hard, replaced and it ran good again. The pump diaphragm was fine since it was the tan fiber one.

ezflyr

My Feedback: (32)

Hi guys,

Thanks for the suggestions! I ordered a couple of carb. rebuild kits today. I'll report back after I perform the work and re-test the engine.

Thanks,

John

ezflyr

My Feedback: (32)

Hi All,

Well, I rebuilt my G20ei carburetor today, a Walbro WT-811, with the Walbro K20-WAT carb. rebuild kit I purchased from eBay. After I disassembled the carb., I gave the entire assembly a good cleaning with Carb. and Choke Cleaner. Following the clean-up, the re-assembly went very smoothly, and I had the entire carb. back together in about 10 minutes. The only question I had while re-assembling the carb. was the orientation of the 'vent' hole on the metering diaphragm backplate? I doubt it matters, but can anyone tell me if the hole needs to face a certain direction?

Overall, the carb. was in very good shape, and quite clean inside. I did notice that the metering diaphragm had several creases in it, and was not as supple as the new replacement part. The gaskets throughout the carb. were also somewhat hard, and dry. I'm cautiously optimistic that this rebuild is going to return this engine to it's former well-behaved self!!!

I hope to run the engine in the next few days (unfortunately it's cold here in the Boston area!), and when I do, I'll report my results!

Thanks,

John

All Day Dan

My Feedback: (5)

John, it faces to the rear. Do you have this exploded view? Dan
http://wem.walbro.com/walbro/product...m=WT%2D811%2D1

ezflyr

My Feedback: (32)

Hi Dan,

I'm not sure what you mean? To the rear of what? To the rear of the carb., to the rear of the airplane? What?

I'm talking about a small hole in part #8 on the diagram you referenced. I can't see any hole in that piece on the diagram!

Thanks,

John

karolh

The positioning of the diaphram plate with the vent hole is not critical and so the plate can be fixed in any orientation.

Karol

All Day Dan

My Feedback: (5)

It's usually towards the rear but Karol is right. Dan.

av8tor1977

My Feedback: (6)

Preferably the hole in the diaphram cover should be oriented away from the prop blast. If it receives prop blast, or false positive pressure from a cowled engine, it will make the engine go rich in flight.

AV8TOR

MercerAUST

Try replacing the spark plug if you still have problems.

ezflyr

My Feedback: (32)

Hi All,

We had a nice day here in the Boston area today, so I brought my Hangar 9 1/4 scale Cub out for an engine run, and test flight following the carburetor rebuild. Man, what a difference rebuilding the carb. made!! The engine ran extremely well, with a smooth idle, great transition, and fantastic top end!! I put five flights on it before the sun got low, and the temps started falling, and my fingers got cold !

Thanks to all that responded to my earlier request for help!!

John

mogman

Good news, glad it all worked out for you.