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Old Dec 12, 2012, 08:38 AM
Complete RC Idiot Savant
The Netherlands
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Yes, that should work, but keep in mind, the engine will immediately flood if it stalls, and will also have a tendency to flood before starting....
That is why normally carbs have typically regulators or float-bowls....

Brgds, Bert
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Old Dec 12, 2012, 10:14 AM
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Originally Posted by kentli22 View Post
just for study purpose, provided it is done at the bench, if I have a fuel tank positioned at a higher place and feed fuel directly to the carb by gravitation, without going through the pumb at all, will the engine be running correctly since the ample supply of fuel is guarranteed by gravitation?
Yes you can do that. But the engine might have a tendency to flood out as the fuel can flow more easily. I would position the fuel tank so it is centered on the carb, maybe even slightly below (most ARF and many kit planes tend to have the fuel tank positioned a little low anyway). Then test run the engine like that.

One thing though is now with the engine drawing its own fuel, is the needle valve setting will change a little as the fuel tank empties (fuel level changes). So you'll need muffler pressure to help compensate for it. But you'll need to run the engine a little on the rich side of course.

You can try running the engine with a 1/4 full fuel tank and adjust it to run like that, then stop the engine, fill up the fuel tank, start the engine and see if the engine runs too rich like that or not.
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Old Dec 12, 2012, 02:59 PM
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When they become available as parts, I will buy a carb for the new Evo 10 cc spark engine (with regulator built in - as was intended for this engine, but abandoned) and fit it.

Hopefully that will be a permanent solution. Tidier as well without the separate regulator unit.
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Old Dec 12, 2012, 05:18 PM
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I've got the engine and everything esle all set up now on the bench once again , with the pumb/regulator & Carb all set up according to the supplementary sheet diagram. The LSN 6 turns out, the HSN 1 and 1/2 out, throttle half open as Earlwb instructed, new RCexcl spark plug (the speak plug cap missing the spring ). I will try to start it sometime today.
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Old Dec 12, 2012, 08:29 PM
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Didn't you have a couple of small springs in the small plastic bag included with the CDI unit? There is also a couple of plastic clips to help keep the connectors together too. Along with a length of twist on plastic tubing so you can wrap the spark plug wire and maybe some of the length of the timing sensor wires.

Remember idle is about 1/2 open on the carb throttle. The engine does appear to be running rich and spitting out fuel too, this is normal. Some people tend to mistake that for running too rich at idle. But if the engine is idling Ok for a while, then it isn't too rich at idle. The port timing on the engine is fairly aggressive and that leads to more spitting out of the carb.
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Last edited by earlwb; Dec 12, 2012 at 08:31 PM. Reason: typo correction
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Old Dec 12, 2012, 10:44 PM
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I lost the 2 small springs, is it OK to test run it on the bench without it? all the rest of the connections are proper.
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Old Dec 13, 2012, 05:35 AM
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Yeah it'll work without the two little springs. The springs are to help improve the shield's contact with the engine crankcase so that it is grounded better to the CDI unit. The spring is not critical to the engine being run. The spring just helps improve the contact to ground. I usually test run the engines without the spring as it can be easy to loose them when I am outside test running the engines. Now it is possible that the spring might help reduce radio interference or noise in some cases with a better ground connection to the engine's crankcase.
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Old Dec 13, 2012, 07:22 AM
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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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Old Dec 13, 2012, 07:32 AM
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Be sure you have the collar that has the magnet for the hall sensor around the right way! it can be fitted 180 degrees out and you will spin the motor until the end of time with no luck.
Actually isn't the end of time the 21st ?
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Old Dec 13, 2012, 07:41 AM
Complete RC Idiot Savant
The Netherlands
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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.
If the spark jumps outside the engine, it WILL jump inside the engine.

It can be either the collar being wrong as brace said, or the mixture is too rich or too lean.

Gas (petrol) behaves a bit different compared to methanol: where methanol still tends to "kick" a bit on the edges of the ignitable range (and it has a very wide ignition range), Gas outside its ignition limits it will absolutely refuse to ignite, and the ignition range is relatively very small, which is why carburation on a gasser is always a lot more critical and problematic compared to glow.

Brgds, Bert
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Old Dec 13, 2012, 09:12 AM
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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.
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Old Dec 13, 2012, 09:19 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.
It can be either the collar being wrong as brace said, or the mixture is too rich or too lean.

Gas (petrol) behaves a bit different compared to methanol: where methanol still tends to "kick" a bit on the edges of the ignitable range (and it has a very wide ignition range), Gas outside its ignition limits it will absolutely refuse to ignite, and the ignition range is relatively very small, which is why carburation on a gasser is always a lot more critical and problematic compared to glow.

Brgds, Bert
Not True Bert!
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Old Dec 13, 2012, 09:27 AM
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is the collar the big blue color ring with a silver round dot on the surface, set right below the hall sensor? if do, I did switch it around about 30 minutes prior to I finally got it started. this thing must had somehow misplaced without me knowing it. I didn't really know what this thing does, I just switched it because there was nothing else I could do. but of course it didn't start immediately after that, but it must be because I was so confused I didn't know what I was found any more.
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Old Dec 13, 2012, 09:33 AM
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Bert is right.That engine needs very careful priming.If less or overprime then impossible to start.Then HSN must be closed and flip it until start and clean the crankcase.
My next try will be removed regulator needle and an adjustable restricted return line with y connection to fuel line.
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Old Dec 13, 2012, 09:34 AM
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it seemed to idle just fine without quitting at around 2600-3000rpm range, to restart was as easy as the starter applied, there was still occational bubbles feeding to the carb, but didn't seem to cause problem. the pumb is mounted behind like as it was behind the firewall. I didn't do more than 6500rpm yet, because it is night time at where I'm now.
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