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Old Dec 13, 2012, 10:41 AM
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I guess we all forgot to have you check the thrust washer to ensure it wasn't on 180 degrees reversed. It is easy to have it happen when changing props, etc. Good catch though.

The idle will get better as the engine breaks in more. The pump/regulator can sometimes be difficult to get all the air bubbles out of it. Also it is sensitive to engine vibration too. I usually isolate it with some padding, and a shelf or something with a velcro strap, so it doesn't move around too much.

I think you are doing good, you have made progress, it is running. It may take a while before you can hand flip it to start.
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Old Dec 13, 2012, 10:45 AM
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Turk,
"Then HSN must be closed and flip it until start and clean the crankcase" ---what does this mean? do u mind explain it in a way that is easier to understand? thanks.
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Old Dec 13, 2012, 10:48 AM
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earlwb, the collar = the thrust washer = the blue color ring I was talking about?
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Old Dec 13, 2012, 10:50 AM
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maybe the ngh gt9 isn't so bad after all, haha
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Old Dec 13, 2012, 11:36 AM
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Quote:
Originally Posted by Brutus1967 View Post
If the spark jumps outside the engine, it WILL jump inside the engine.
Unless there is a problem with the high tension lead. If the lead or cap become damaged, the spark can jump in the plug when taken out of the engine, but jump inside the cap or lead in the area of cracked insulation. I've had this happen and if you listen very carefully you will hear the spark outside the engine. It's tricky to diagnose.

Greg
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Old Dec 13, 2012, 11:51 AM
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Originally Posted by gkamysz View Post
Unless there is a problem with the high tension lead. If the lead or cap become damaged, the spark can jump in the plug when taken out of the engine, but jump inside the cap or lead in the area of cracked insulation. I've had this happen and if you listen very carefully you will hear the spark outside the engine. It's tricky to diagnose.

Greg
You need a higher tension for a spark "under compression" than in barometric circumstances, so even there is a spark outside you don't know for sure there will be a spark inside the cylinder under compression!
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Old Dec 13, 2012, 12:16 PM
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Originally Posted by Taurus Flyer View Post
You need a higher tension for a spark "under compression" than in barometric circumstances, so even there is a spark outside you don't know for sure there will be a spark inside the cylinder under compression!
That might be valid for old motorcycles and cars, lawnmowers and snowmobiles, outboard motors etc, with their separate CDI units, HV-coils, spark leads and possibly distributors, grounding via the engine, frame/chassis etc etc, all having connectors that can become rusty and cause voltage drop. Or because the crank is not spinning fast enough for the magneto to give a powerfull spark.

But it is very unlikely* in a battery powered, sealed unit without external connectors or HV coils, a unit that is factory tested. Such unit produces HV of sufficient voltage, or it doesn't produce anything at all. It doesn't have the voltage drop usually associated with bad contacts. That is what I meant by, if it sparks outside, it sparks inside.

A bad or damaged plug-lead sparking in the cap or somewhere else might be possible though. But that should show itself immediately by removing the plug cap and checking for (audible) sparks.

Brgds, Bert

*very unlikely as in: I have not yet heard of it in these kind of ignition systems, ever....
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Old Dec 13, 2012, 12:20 PM
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thanks. I am trying to start it now, so far no luck because the spark doesn't fire except when taken out to test. I can see fuel reaching the carb, will keep trying.
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Originally Posted by kentli22 View Post
it finally started, after 2 hours of not one fire from the spark, regardless of different needle settings, just wouldn't fire. Just before I quit, I dropped a few drops of fuel into the carburetor hole, then it just fired once I applied starter.
Basically meaning: it did spark all the time like I said, just the mixture present in the combustion chamber at that moment was outside the ignitable range, even if (given the fact that it started and ran) the needles were somewhere in the ballpark.

That is the reason why lots of petrol (gas) engines are equipped with a choke or need priming in order to start.

Brgds, Bert
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Old Dec 13, 2012, 12:40 PM
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I know how to prime an engine that comes with a choke and flip it with the choke closed until it pop, then I know the engine is ready to start once I open the choke. But with the NGH 9cc which doesnt has a choke, how do I know when the priming is enough or when it is not enough?
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Old Dec 13, 2012, 01:03 PM
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Now I freely admit, I am just guessing here, but this is what the Zenoah Car engines really like for breakfast: close the choke and pull the rope until it kicks. Open the choke again and pull untill it starts.
Usually, with this procedure the engine kicks on the first or second pull, and starts on the first consecutive pull after the choke has been opened.

In your case, use your finger or a plug with a small orifice in it to partially close the intake (choke valves usually are not fully closing off the intake) and flip the prop untill it kicks (or give VERY short bursts with the starter).
Remove finger or plug, and continue starting until it fires.

Alternative, you can switch off the ignition, and first flip the engine once while closing the intake with your finger. Try starting. Then two flips, try starting again. Then three.... etc etc, until you get a feeling for what the engine likes.

Or you just use the "droplet count" like you did before.

Just what is most convenient for you....

Brgds, Bert
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Old Dec 13, 2012, 01:25 PM
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Quote:
Originally Posted by Brutus1967 View Post
That might be valid for old motorcycles and cars, lawnmowers and snowmobiles, outboard motors etc, with their separate CDI units, HV-coils, spark leads and possibly distributors, grounding via the engine, frame/chassis etc etc, all having connectors that can become rusty and cause voltage drop. Or because the crank is not spinning fast enough for the magneto to give a powerfull spark.

But it is very unlikely* in a battery powered, sealed unit without external connectors or HV coils, a unit that is factory tested. Such unit produces HV of sufficient voltage, or it doesn't produce anything at all. It doesn't have the voltage drop usually associated with bad contacts. That is what I meant by, if it sparks outside, it sparks inside.
A bad or damaged plug-lead sparking in the cap or somewhere else might be possible though. But that should show itself immediately by removing the plug cap and checking for (audible) sparks.

Brgds, Bert

*very unlikely as in: I have not yet heard of it in these kind of ignition systems, ever....
Bert,
The fact is, theoretical a spark in barometric circumstances do no guarantee you will have a spark "under pressure".

TF
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Old Dec 13, 2012, 01:45 PM
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Brutus,
What you had explained are very clear to me. Thanks.
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Old Dec 13, 2012, 03:49 PM
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Originally Posted by Taurus Flyer View Post
Bert,
The fact is, theoretical a spark in barometric circumstances do no guarantee you will have a spark "under pressure".

TF
Yea yea yea, and theoretical, bees can't fly cuz their wings are to small....

We're talking reality here: if that RCexl unit sparks outside the engine, it sparks inside (except when the plug lead is damaged.... we got that....)

I will not bore you with the cases that a spark was confirmed (visually) an igniteable mixture was confirmed present, and still no ignition occurred....

Brgds, Bert
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Old Dec 13, 2012, 05:47 PM
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Originally Posted by Brutus1967 View Post
Yea yea yea, and theoretical, bees can't fly cuz their wings are to small....

We're talking reality here: if that RCexl unit sparks outside the engine, it sparks inside (except when the plug lead is damaged.... we got that....)

I will not bore you with the cases that a spark was confirmed (visually) an igniteable mixture was confirmed present, and still no ignition occurred....

Brgds, Bert
Short note, no nonsense!

The voltage needed on a high voltage system to produce a spark depends on the size of the sparking plug gap and the gas pressure within the cylinder.
A normal gap is about 0.6 mm (0.024 inch), and although only a small charge of about 600 volts is required to produce a spark across this gap in the open air, it will take 10-50 times this voltage to fire a sparking plug that is under combustion pressure in a cilinder
The combustion pressure should be take into account when an ignition system is beiing tested - a spark produced at a plug outside the cilinder does not guarantee that it will be spark when it is subjected to cilinder pressure.

Success with trouble shooting.

TF
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Old Dec 14, 2012, 12:59 AM
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Originally Posted by kentli22 View Post
Turk,
"Then HSN must be closed and flip it until start and clean the crankcase" ---what does this mean? do u mind explain it in a way that is easier to understand? thanks.
I mean if overprimed(not mentioned less primed because anytime you can start it since it will take time) there is no way to start it until having a proper mixture to ignite.Maybe a very strong starter and playing with throttle may make it start but mostly pilot have to stop the fuel feed(by closing the HSN because removing the fuel line will cause fire risk due to pumping fuel outside).Then flip or apply starter until crankcase mixture begins to ignite.After excessive fuel burned and engine stopped then you may again to prime it and restart.It is only a matter of getting used to with it.

Quote:
Originally Posted by kentli22 View Post
maybe the ngh gt9 isn't so bad after all, haha
Engine is great.Only fuel feed is problematic.
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