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G20 ei won't start anymore

Old 05-13-2008, 09:21 PM
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mdegreve
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Default G20 ei won't start anymore

Can you please help ?
I had a dead stick in flight and couldn't manage to get the plane back safetly so I landed in the weeds and ripped off the landing gear.
This has now been fixed but to my surprise, the G20 ei won't start anymore.
The ignition is OK, there is fuel and the carb looks fine. BTW, nothing has been damaged with the exception of the landing gear.
I tried to use an electric starter to start the engine but with no success. I'm running 1:100 Opti-2 synthetic oil since the start and with great suc.
Any idea where to look at ?

Happy flying,

Mike
Old 05-14-2008, 08:10 AM
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Walt and Sage
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Default RE: G20 ei won't start anymore


Check that BOTH carb gaskets are NOT together on one side
of the carb block...

A friend of mine and most of our club worked on his for hours
before we noticed that..

Walt...

Old 05-14-2008, 10:32 AM
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mdegreve
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Default RE: G20 ei won't start anymore

Hi Walt,

No, they aren't. I had 40 successful flights before the problem has shown up.
What is strange, is that I removed the carb today, and filled directly the cylinder with gasoline and still, the engine won't start.
With regards to my initial post, I can see the spark is OK.
Could it be a problem of ignition timing ?
The magnet is still in position and nothing is loose or broken.
The spark plug was dark and greasy, indicating that the low end setting was a little too rich.
Also, I noticed that the piston was brown for let's say the first 1/3 inch.

I don't know if the problem occured in flight, or is a consequence of the bad landing.
I'm more and more prone to consider that this was an in-flight problem.

Happy flying,

Mike
Old 05-14-2008, 08:09 PM
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tkg
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Default RE: G20 ei won't start anymore

A quick of the timing on an G20... At TDC the magnet should be 6-8mm past the sensor (CCW)
Old 05-15-2008, 02:27 AM
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togatoga
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Default RE: G20 ei won't start anymore

Sounds like an ignition module problem. A spark does not assure that the igniton module is working fine, I found that out the long way! The zenoah module is prone to failure and one of the things it does is not go into retard mode to start the engine. The engine becomes almost impossible to start.I would swap the ignition unit or get the CH rcexl unit which requires no additional adjustments and you can use the original sensor and give it a try.
Old 05-15-2008, 06:57 AM
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Default RE: G20 ei won't start anymore

Thanks for this information. I just checked the timing and it was OK. I ordered a new ignition today.
It's a pity that the Zenoah stock ignition is not reliable. The engine has only 40 flights.
Sometimes, every 10-15 flips or so the engine pops, but won't start.
Indeed, looks like an ignition problem and more than probably, it happened in flight.
I will keep posting news about the results when the new ignition will arrive.
Old 05-15-2008, 07:26 AM
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Default RE: G20 ei won't start anymore

It will be interesting to see if the ignition is the culprit. Hope you are on the right track so that you can get her going again.

Karol
Old 05-17-2008, 08:05 AM
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Default RE: G20 ei won't start anymore

I would check the fly wheel key has not sheared.

I hope your not actually mixing your oil at 100:1, even your slow reving <10k plane engines would be running better and longer @ 32:1

The place to look for lack of oil damage is lower of piston under exhaust port.
Old 05-17-2008, 01:28 PM
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Default RE: G20 ei won't start anymore

Check the spark at night with lights turned out... a reliable spark will be bluish in color. A yellowish spark will fire the engine occasionally when the mixture is perfectly suited but not consistently enough to run.

Also, the spark needs to hit the ground bar, if the spark jumps from the electrode and grounds somewhere other than near the tip of the ground bar, the plug has a problem and the spark is not interfacing the fuel mixture in an optimum position.

Either of these two issues could produce the occasional firing but not starting.

Generally a carb problem can be diagnosed by first pulling the plug and insuring it is dry. Then priming the plug hole with a small amount of fuel, reinsert the plug and after several flips if there is no burst of running, the problem is likely ignition. If there is a burst of running then the problem is likely a carb issue.
Old 05-24-2008, 08:28 AM
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Default RE: G20 ei won't start anymore

Mike, did you resolve the problem yet?
Old 05-26-2008, 04:55 PM
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rodman293
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Default RE: G20 ei won't start anymore

Hi Medegre, listen to me I had the same thing happen to me with a FTL-45, (chinese eng) and like you I coud not get it started, after it was runing ok, and apprently for no reason, well let me tell you that after many hours of trying to resolve the problem, and many people in the internet trying to help me, I found the problem almost by mistake, I was going to check the half moon coter pin in the crankshaft where the flywheel with the magnet is, to se if it had sheared, but it was Ok, when I inspected it, I noticed that the crank seal was kinda crooked, and I removed it to inpect it, there is a little spring that looks like a round doughnut that goes on the inside part of the seal, and the spring was indeed broken, the seal was cracked too, without this small little spring the crank does not seal well, and it does not let the crankase pull a vacum, when the cylinder moves up and down, so the engine does not draw the fuel insde the cylinder, and it wont start no matter how many times you flip the prop, so what am telling you is, to test and see if the motor draws fuel into your carb, by choking it, you should see gas in your finger with no more than 2 or 3 flips of the prop, if you do not see your finger wet with gas when you choke it, or if it takes like 10 or more flips to draw gas in the carb, then you got a vacum leak in your motor some where, either one of your seals is bad, or one of your carburator gaskets is not sealing well, or you put the gaskets the wrong way, there is a vent hole in the carb, that has to go thru to the crank case, to act as a pump for your diaphram, in the carb to pump the gas into your carb, and if you put the gasket with the hole in the wrong place and blck the hole, the engine will not start, because is not drawing fuel in, I don't think that you CDI is bad, because they either work or not there is no midlle ground there, and your carb does not go bad, from a simple crash as you said you had, unless you cracked the carb mount or something like that, like I said check to see your seals are sealing, and your gaskets are not leaking, and then try to start the engine again, hope this helps . C Rod. (rodman293)
Old 06-07-2008, 09:52 AM
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Default RE: G20 ei won't start anymore

Well, it seems that the problem has been resolved. Upon the advise of togatoga, I bought a new ignition modules designed to be a replacement from the original one. They are sold by Adam at BCMA engines. The engine fired immediately and guess what.. I have now a reliable idle around 1600 rpm compared to 2100 before. With this new module, my JXF 17x6, previously running at 8100 rpm now turns at 8230 rpm. This an additional static thrust of 0.42 lbs and makes a huge difference in such a small plane (Seagull Yak 90).
Thanks to all for your help as I couldn't make it so easily without all of you.
Togatoga has a good lesson for the less experienced of us, as I am : It's not because there is a spark that the ignition is working !

Happy flying,

Mike

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