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NGH 38CC 4 stroke

Old 04-26-2015, 06:47 AM
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Just thought I'd post an update on my FG38. Having taken everything out of the model I ran the engine on the test stand with the test stand components, tank, battery etc. It ran OK - not brilliant but it ran. Used a DC variable power supply for the ignition and found it was happy anywhere between 4.8V and 8.4V so it clearly wasn't the problem.
I then started taking the model components out and using them on the test stand.

I did find a small air leak in the fuel tube to the carb which made matters worse i.e. the engine ran rougher and the 'idle' was worse. At this stage idle was still +2500 rpm! so not very impressive at all. Probably with that air leak when in the model and the extra shaking of the fuel in the tank with no wings attached accounted for the very poor performance in the model.

At this point I was getting 6500 rpm top and still only 2500 rpm idle so clearly some investigation was in order.

1st thing - throttle stop screw was too far in so idle was limited by that. That got me down to 2300 rpm but lower than that and the engine would abruptly cut when the throttle was opened - often throwing the prop.

2nd: Tappets both inlet & exhaust had zero clearance when hot, exhaust had v.slight clearance when cold. Reset to 0.05mm when cold.
Top end improved to 6700 rpm and lowest idle now 2200 rpm - but still cutting when throttle blipped if taken lower.

3rd: Added gaskets to inlet either side of Teflon spacer as per SJN's post on page 12 - no change.

4th: Checked timing. It was set at 55 deg TDC!!!! Adjusted down to 35 deg TDC (lowest I can get without filing slots in the Hall sensor bracket).
Top end still 6700 rpm, lowest idle now 1800rpm and much less vibration. Smooth pick up from all throttle settings.

At that point a I decided to refit it back in the model and run it there - this time with both wings fitted to help damp out the fuselage shimmy! It runs fine in the model with the same rpm range 6700-1800. I would like the idle to be lower but I can live with that and see if it improves with some running. Brian Winch reported 1500 rpm on a 19x10 but didn't say if that was a light wooden prop or heavier composite type. Also I am still running with a 20:1 mix - that may affect things. I will try moving to 35:1 when it has had a few shake down flights.

So conclusions: Nice engine shame about the factory settings. If you are still reading this thread Mr Michael Chow I am afraid I consider this pretty poor quality control.

That said I am still looking forward to operating this engine.
Old 04-26-2015, 07:59 AM
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Niice you got the engine to run. i dont think you can expect a lower idle. i think both mine is about 1800rpm
Old 04-26-2015, 08:11 AM
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Thanks for that. Saves me chasing the impossible.
Old 04-26-2015, 08:40 AM
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Originally Posted by tyor
Niice you got the engine to run. i dont think you can expect a lower idle. i think both mine is about 1800rpm
http://youtu.be/5xaiAR8Yelc Prop in the video was an 18x8 MAS "K". It turned a 20x8 MAS Classic @ 6500 RPM.

Last edited by SrTelemaster150; 04-26-2015 at 08:42 AM.
Old 04-26-2015, 09:09 AM
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you cant compare a saito and a ngh

I got 5900rpm with a 20x8 on the ngh I have in the storch.
https://www.youtube.com/watch?v=gBCLrpipVyA
Old 04-26-2015, 09:14 AM
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Originally Posted by SrTelemaster150
http://youtu.be/5xaiAR8Yelc Prop in the video was an 18x8 MAS "K". It turned a 20x8 MAS Classic @ 6500 RPM.
I agree. Different engine different prop. Can't see the relevance to this thread. I have an ASP 120 converted to gas - also has a lower tick over.
Old 04-26-2015, 11:25 AM
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How do you get on with hand starting? I find it is fine once the fuel lines are full and the carb primed but I can't get to that condition with out first using an electric starter.
Old 04-26-2015, 11:42 AM
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I use starter most of the time But on a warm engine it start easily by hand.

It helps if you solder the hole in the choke valve?
Old 04-26-2015, 04:51 PM
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Originally Posted by DoctorG
I agree. Different engine different prop. Can't see the relevance to this thread. I have an ASP 120 converted to gas - also has a lower tick over.
The thread could be about electric boats and Sr tele would send u a vid of his saito running ignition ! Winch usually only runs wood props on twin petrol 4 stroke engines not the singles so I would think he;s referring to the " plastic " props . Cheers the pope
Old 04-30-2015, 11:30 PM
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Notice in several threads the mention of timing. Is there a simple methodof checking this on the GF38?
Old 05-01-2015, 04:48 AM
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Originally Posted by SrTelemaster150
http://youtu.be/5xaiAR8Yelc Prop in the video was an 18x8 MAS "K". It turned a 20x8 MAS Classic @ 6500 RPM.
Originally Posted by DoctorG
I agree. Different engine different prop. Can't see the relevance to this thread. I have an ASP 120 converted to gas - also has a lower tick over.
Some of the timing specs I see for this engine with the OEM ignition seem a bit bizarre. Is this a Hall effect triggered CDI?

The relevance is that this being a larger displacement engine than the FA-180, (CDI) it should have an even lower reliable idle.

I wonder what a conversion to a C&H module or one of the Chinese clones would do for user friendliness. A total advance of about 28 BTDC should make peak power in an air cooled 4-stroke "gas" engine.The C & H module set at 28 full advance would then retard to 4 BTDC for easy starts & reliable idle.

The early Saito FG gas engines benefited from the C&H upgrade.

Last edited by SrTelemaster150; 05-16-2015 at 04:03 AM.
Old 05-01-2015, 11:05 AM
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Originally Posted by discus-fly
Notice in several threads the mention of timing. Is there a simple methodof checking this on the GF38?
No simple method. You need a timing disc attached to the prop driver and then find top-dead-centre TDC and set disc to zero. Then connect the ignition system and find out where it sparks. You can get a tester which I believe replaces the spark plug or possibly the ignition which makes it a bit easier (I haven't tried one) as actually seeing or hearing the spark can be tricky. There are several videos around to show how to find TDC and set up the ignition. I will up load a video of checking mine to YouTube and post a link here.
Old 05-01-2015, 12:15 PM
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This is one of the better videos by a guy who knows what he is talking about. The owner of CH Ignitions.

https://www.youtube.com/watch?v=DTwyptJpJL0
Old 05-01-2015, 01:03 PM
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Originally Posted by DoctorG
No simple method. You need a timing disc attached to the prop driver and then find top-dead-centre TDC and set disc to zero. Then connect the ignition system and find out where it sparks. You can get a tester which I believe replaces the spark plug or possibly the ignition which makes it a bit easier (I haven't tried one) as actually seeing or hearing the spark can be tricky. There are several videos around to show how to find TDC and set up the ignition. I will up load a video of checking mine to YouTube and post a link here.
Originally Posted by capnpaul
This is one of the better videos by a guy who knows what he is talking about. The owner of CH Ignitions.

https://www.youtube.com/watch?v=DTwyptJpJL0
I use a fixed pointer. With that method I do not use a "target" reading, but the 1/2 way value is still employed.

http://www.rcgroups.com/forums/showthread.php?t=1774802

I do not employ a buzzer or light. I instal the module with a spark plug clipped to the cap. (the C&H McDaniels plug cap has a bout in grounded shield) In then observe the reading as the mag repot passes under the Gall sensor & listen for the spark.

Adrian's method is handier if you have the buzzer, but it can still be accomplished W/O the buzzer.

My 34 BTDC setting is for use with methanol. Gasoline should be set at about 28-30 BTDC.

These methods are for use with the C&H or RCEXEL modules with 24-25 spark retard for starting that empty Hall effect triggers. They may not work with the standard NGH systems.
Old 05-02-2015, 02:43 AM
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Originally Posted by DoctorG
No simple method. You need a timing disc attached to the prop driver and then find top-dead-centre TDC and set disc to zero. Then connect the ignition system and find out where it sparks. You can get a tester which I believe replaces the spark plug or possibly the ignition which makes it a bit easier (I haven't tried one) as actually seeing or hearing the spark can be tricky. There are several videos around to show how to find TDC and set up the ignition. I will up load a video of checking mine to YouTube and post a link here.
OK video should be viewable here https://www.youtube.com/watch?v=vyODVsPMkjE which shows the engine as I received it and also my slightly 'different' way of determining TDC using a drop clock.
Old 05-16-2015, 01:56 AM
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As the Tiger Moth cowl is very slim manufactured a suitable exhaust.

Item was fairly simple to construct using 1/2 x 1 inch section tube and 10mm copper pipe. All joints are made with silver solder. yet to run the engine though.
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Old 06-07-2015, 12:46 PM
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sds-hobby have a muffler that works perfect with this engine. I tried it now on my aichi d3a1 val.

http://www.sdshobby.com/engine-fuel-...at-engine.html

https://www.youtube.com/watch?v=a3WovtTO-3M
Old 06-07-2015, 01:11 PM
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Thanks for that Tyor. I now have one on order.

Alf
Old 06-08-2015, 06:46 AM
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I realize some places have stricter noise regulations than others but my NGH 38 FSG is quieter without a muffler than a Zenoah 26 with.
Old 06-08-2015, 06:52 AM
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yes 4-stroke engines are quieter than 2-stroke engines. but with the muffler you get rid of the "hard" sound.
Old 06-08-2015, 06:55 AM
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I like the hard sound
Old 06-11-2015, 04:48 PM
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I just received the muffler Tyor informed us about from SDSHOBBY. Haven't tried it on the engine, but what I can say is it looks good and arrived very quickly. About one week from ordering to get from China to New Zealand. For the price that seems excellent!!
Old 06-12-2015, 04:44 AM
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I tested the mufler and have zero difference in topp rpm with the muffler on
Old 06-22-2015, 10:54 AM
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opened one of my engines today. Just to se how the bearings and sylinder looks after ca 2years of use. After viping of the oil it looks almost as new
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Old 06-22-2015, 11:17 AM
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What oil ratio have you been using?

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