NGH 9cc gas engine thread - Page 82 - RC Groups
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Dec 19, 2012, 09:40 PM
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Dubro 8x32 fittings

Anyone know where the best place to order the dubro 8x32 fittings?

I have the pump rebuild kit, felt clunk and the spring. I just need the fittings to complete the rebuild.

My story is like many others. At first I thought it might just be possible that my ngh 9 will be the one that runs great without to much modification.

After 100 or so flips I finally got it to fire. I kept the needles at factory and thought I would go from there. There were so manny bubbles I really did not even attempt to tune it. It did scream with a 10x7 APC though but only for a second as I didn't want to accidentally run it lean with the bubbles in the line. I even built a bracket to hold the pump behind the engine that is of very thin aluminum to absorb the vibrations. It did seem to make a very slight difference if I held the pump between my fingers to further dampen the vibrations, but not much. For the most part there were no bubbles visible from the tank line, but I did see one or two every 3 to 4 min. The carb line had maybe one every 2 seconds.

I have a 50cc stick that I like to fly and this seems to be the answer to get rid of glow fuel. I hate the stuff!
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Dec 19, 2012, 10:24 PM
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earlwb's Avatar
I got all of mine at my local hobby shop. But online most of the online stores have them too. Dubro number #539 pressure 8-32 fittings. Tower Hobbies stock number LXD623.
Dec 19, 2012, 10:56 PM
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Thanks Earlwb! Got them ordered

Were you going to give the Evo 10cc carb a shot on the ngh9?
Dec 19, 2012, 11:03 PM
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earlwb's Avatar
Not really a reason, I can get the OEM carb to work OK along with the pump/regulator. I do plan on getting a Evo 10cc myself to play with too.
Dec 19, 2012, 11:15 PM
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brace's Avatar
The evo is on my wish list but there are a few other items before it. However if a thread starts up I will be happily following it
Dec 20, 2012, 02:51 AM
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Objectives achieved. Result impressive.

Both nose forward and nose up, rpm remains stable and constant from idle to WOT which is about 500rpm higher when nose up. Transition from low to high or vise verse are both smooth and easy. No more sudden burst of rpm nor misfire at any throttle position when I have the needles adjusted correctly. Priming takes only about 5-10 flips. No threat of engine quitting both nose forward or nose up. The engine sound is beautiful provided that I have replaced the muffler with a stock OS 46 muffler.

(1) My needles positions have changed a lot from before. Now LSN 1 and 1/2 out, HSN a few clicks less that half out.
(2) when I add a 3ft long 12mm alumimum pipe to the end of the muffler to went the smoke outside the window, I found out that the WOT increased about somewhere near 1000rpm to reach near 11,000rpm, idle rpm remains unchanged. Taking away this 3ft long pipe the WOT drop to about 9,500-10,000rpm, but it runs really comfortable at this rpm both nose forward and nose up. IF I lean it more to reach another 500rpm, then it will eventually quit when nose up.
(3) I use 11*5 apc with a small spinner.
(4) Carb intake is about 1/3 open at idle at about 2300rpm
(5) bubble almost non exist from pump to carb, but there is little bit of fresh fuel stain at the butttom of the foam that packed the pump, I suspect there is a minor leak of fuel at the pump nipples or pump seal because one of the 4 screws on one side can't tighten really well.
Dec 20, 2012, 03:41 AM
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brace's Avatar
Well done kentli22, now go out and fly it
Dec 20, 2012, 07:38 AM
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earlwb's Avatar
Good job Kentli22, looks like you are ready to go flying now. The RPMs sound about right for the engine. The 11x5 prop seems a little on the small side to me, as my engines like the 11x7 size props better. Maybe a 11x7.5 or 11x8 prop may be even better.
If the pump/regulator is working good, don't worry about a little bit of seepage. it might be the carb spitting out some fuel more than the pump/regulator doing it.
Dec 20, 2012, 09:14 AM
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DarZeelon's Avatar

A ringed engine becoming fully broken-in, does make changes for the better in its running qualities.

As to the power available from the engine... It is rather mediocre 0.49 HP, calculating from your 10,000 RPM on an APC 11x5; despite it, as earl wrote, being quite small for this engine.

I would expect about twice the output from this engine.
Dec 20, 2012, 01:29 PM
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miltac's Avatar
Ive been fowlowing this thread for a while now and finally decided to give one a try.

its mounted on a SPAD Debonair replacing an evolution .46. With the president taking his vacation here I wont be able to fly it until the 7th of January.

so far I have about 15 minutes of run time with the needles set at 6 and 2.5 trying to get some time on it before I mess with the needles.

I rebuilt the carb with a walbro kit as sugjested in this thread, there are no air bubbles and i only have to rock the prop a handfull of times to prime the carb.

I am hoping to get more time on it today and start getting the needles set.
Last edited by miltac; Dec 20, 2012 at 01:31 PM. Reason: added pic
Dec 20, 2012, 11:47 PM
Registered User

I got mine stuck on a SPAD Stick. I guess we will see how these things fly plastic! Maybe I will see you at the airfield. I live on town side
Dec 21, 2012, 12:07 AM
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Thanks everyone here for helping me. I will mount the engine on a plane and flying this weekend. I have some 12*6 wood prop that I can try on it.
Of all the modifications that I have done:
1) keep the pump/regulator from vibration reduce bubbles fed to the Carb
2) use a felt clunk zip to the last drop plus reduce bubble to the pump.
3) keep the fuel line short from pump to carb ensure enough fuel being pumped to the carb. Does this also directly benefits the nose up situation?
4) replaced with walbro gasket and diaphragm for the pump and regulator, what is the direct contribution of this modification?
5) replaced the bigger nipples from the original 2.5mm to 4mm, what is the direct contribution of this modification?
Dec 21, 2012, 12:18 AM
Registered User
miltec, looks like you had better luck with the pump than me when first running it. if I mount the pump like u, it will feed bubble to the carb and also from pump to tank. but of course when I first ran it in the beginning, I didn't have the gasket and diaphragm changed, so I wonder if this itself is enough to solve the bubble problem without the need to prevent the pump from vibration. I will try to run it without using the foam to pack the pump to see what difference it make.
Dec 21, 2012, 12:32 AM
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DarZeelon's Avatar

I wrote that your engine is very low on power output.
Check why it is.
Dec 21, 2012, 02:57 AM
Registered User
but what do I need to check? I don't know know much about engine at all.
the power output is determined by the max rpm? what are the acceptable rpm ceiling to be considered as acceptable for it's power output?

I think if I let it run in longer and better needles adjustment , the rpm ceiling might become become higher.

Also, Earlwb mentioned that when the engine is actually flying, it was faster. So perhaps the power output is increased when the plane is in the air.

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