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Old Dec 09, 2012, 02:15 AM
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Australia, SA, Adelaide
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Howdy there Turk you certainly have more patience then me . Maybe Michael could come on and help . I see this problem child is gradually being dropped by various dealers worldwide except Hobby King but as they probably wont provide any after sales service they cant loose . The new 38cc 4 stroke seems to be having issues as well which is a shame as the machining looks pretty good inside whether the materials its made from are up to it I guess we will have to wait and see .If this ones a dud I doubt he could recover but theres always a name change and a different anodised colour . Anyway good luck and keep us informed , surely there must be some out there that run out of the box ok and if so I wonder why some are so difficult . I see the evolution brand has just anounced a 10 cc gasser and norvel are testing a 46 size gasser although this is a bit different with no ignition etc which maybe the way of the future with the smaller capacity ones , if these run ok the ngh9 might be toast . Cheers the pope
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Old Dec 09, 2012, 03:05 AM
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Originally Posted by turk1 View Post
Yesterday I have more test runs on GT9.I could have good run on all of the throttle spectrum including good low idling but I couldnt have reliable WOT during nose up simulation on bench.
It seems pump have problem to raise fuel to carb while having some level, at WOT.Seems running good at WOT on nose up but giving any throttle play makes it an absolute stop.
Now I need to change pulse nipples but I dont know how and when I can find 2 of them.
Just for me to understand correctly: it runs WOT with the nose pointed up, but as soon as you change throttle while the nose is up, it stops immediately?

As far as I know, that cannot be a pump problem: if it runs OK with the nose up at WOT, the pump is delivering. if it stops when you change the throttle at nose-up, it must be a regulator problem more than anything else. Problem is I do not see how the regulator gets influenced by the nose-up or nose-level position.
The only thing I can think of is that there is too much distance between needle and regulator.

You might try to change the fuel pressure by trying to increase the spring tension in the fuel regulator (maybe different springs from a Walbro overhaul kit?). Then you obviously need to close your needles slightly, but the relative change in fuelpressure caused by nose-up or nose-down will get smaller, keeping mixture variations in the igniteable range....

Brgds, Bert
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Old Dec 09, 2012, 10:12 AM
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My theory that I developed after a while of working with my NGH 9cc engines, was that the two small size fuel fittings used for the crankcase pressure pulses had too small of a hole or orifice in them to allow for good strong pulses to make it to the pump. I didn't think there was enough room to drill the holes out larger and the single barb on the fittings is rounded and smaller in size and didn't fit the fuel tubing tightly that we use here in the USA (metric size fuel tubing might fit better though). The fittings could have been leaking pressure and acting as resistors to the pulses to some extent too. Tygon tubing would tend to loosen up and pop off the crankcase pressure OEM fitting quite easily too. I had discovered that if the engine was running WOT and the fuel fitting came off the crankcase pressure fitting, the engine continued to run just fine like nothing was wrong. I found that very troubling and it took a while for me to figure it out. That led me to use larger fittings of course.

So I decided to use a couple of larger dual barb Dubro 8x32 fittings and redrill and tap the appropriate holes to fit. That worked out amazingly well for me. For three of my engines, the pump started pumping quite strongly then so that the engine was supplied with fuel under pressure really well. Now when you pull the fuel line off the pressure fitting (albeit with some difficulty) with the engine at WOT (and adjusted to run good), the engine dies from lack of fuel. The larger fittings worked really well for me and one may not need to do much of anything else to the pump/regulator then.

The other optional thing that did help was to use the teflon pump diaphragm as it pumps fuel a little more strongly too. But the blue plastic diaphragm works pretty good too. The black rubber diaphragms seem to get soft and stretch out over time in my experiences with them, thus loosing pumping pressure. But that may be due to the cheap Chinese Knockoff rebuild kits being sold as genuine over here. if I can find a real good genuine rebuild kit then the black rubber diaphragms may be Ok too. I can't tell for certain yet.

I would think that in Europe they may have metric fittings that would be a similar size to the Dubro 8x32 ones here.
One that I came across here that looks promising is a "SKYHolic" branded fitting (A106) bolt on pressure fitting. It is metric size M3.5, and has dual barbs on it. But you may need to use metric size fuel tubing though.
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Old Dec 09, 2012, 12:55 PM
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The Netherlands, NB, Breda
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I used M4. M4 taps are much easier and cheaper to get (they come in standard metric tap and die sets) than M3,5 wich have to be bought at a specialized tool shop. Saito crankcase vent nipples have M5 threads.

I bought my nipples here (item GA19 for crankcase pulse, and GA20 for fuel connections). They also sell larger sizes like M5, and 90 degree nipples:

http://www.prestwich.ndirect.co.uk/hdwraccs.htm

Best regards
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Old Dec 09, 2012, 08:18 PM
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Originally Posted by the pope View Post
...I see this problem child is gradually being dropped by various dealers worldwide except Hobby King but as they probably wont provide any after sales service they cant loose . ..... Cheers the pope
I think the low price that Hobby King is charging has more to do with others dropping the GT9 than it's problems. Hobby King isn't playing fair in my opinion and is hurting the other distributors. With this motor I'd rather pay more just to get the after sales service.

Ray
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Old Dec 09, 2012, 08:30 PM
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I kind of figured the same thing. With Hobby King undercutting the price of everyone else, then the dealers will stop selling the engines. It is normal. I think NGH cut their own feet off in this case.
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Old Dec 10, 2012, 02:22 AM
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Originally Posted by Brutus1967 View Post
Just for me to understand correctly: it runs WOT with the nose pointed up, but as soon as you change throttle while the nose is up, it stops immediately?

As far as I know, that cannot be a pump problem: if it runs OK with the nose up at WOT, the pump is delivering. if it stops when you change the throttle at nose-up, it must be a regulator problem more than anything else. Problem is I do not see how the regulator gets influenced by the nose-up or nose-level position.
The only thing I can think of is that there is too much distance between needle and regulator.

You might try to change the fuel pressure by trying to increase the spring tension in the fuel regulator (maybe different springs from a Walbro overhaul kit?). Then you obviously need to close your needles slightly, but the relative change in fuelpressure caused by nose-up or nose-down will get smaller, keeping mixture variations in the igniteable range....

Brgds, Bert
Hi Bert, yes you are right on your comments depending my explanation but I couldnt express all my test impressions here.I mean as Earl mentioned,it is a pump delivery issue more than regulator which I always insist "working reversely already" So I tried to take regulation on to both needles rather from pump regulator needle.What I saw disturbing ,line fuel was returning to tank when engine stops.That means check valve doesnt work properly.Also during run at WOT engine begins to starve fuel if I dont give it more than enough HSN.I could test it easily making it "let's simulate nose up huh?"It gets immediately starving at very little up positions even.If I can have good pump delivery,I believe I can regulate mixture by needles.So next try will be removing regulator needle and testing unit only with pump function while my changed LSN and HSN would regulate the carb.(because seems I cant have bigger nipples in near future).Then I am hoping to have better fuel delivery eliminating reg. needle restriction.Also I am working on check valves,hoping to make them work properly.Material seems perfect but leaking back,why?
Note: Your point about distance between regulator and needle is true.I must going to try also to keep it closest as possible.
Tks.
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Old Dec 10, 2012, 06:03 AM
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The pump diaphragm has two little flapper valves on it. Sounds like the valves aren't working. The diaphragm may be warped, stretched out, hardened, or shrunk on it. Sometimes just the two little flapper valves are warped or something too. Either that or the fittings and or fuel tube leading from the engine to the pump has a obstruction of some sort in it.

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Old Dec 10, 2012, 07:47 AM
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how could an average rc guy having fun with this loving looking little ening? other than when money and time was not an issue, or when he was capable enough like earlwb.
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Old Dec 10, 2012, 07:52 AM
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I think Hobby King is doing a favor to help cash back on the inventory before it is too late. However, I admire the bravery and gut of Mr. Chow.
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Old Dec 10, 2012, 07:59 AM
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I am a-few-month and a-few-engine new to this non electric rc territory, please excuse me if my comments sounded naive and/or retarted. haha
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Old Dec 10, 2012, 08:08 AM
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I have this NGH engine, it is not workable but i like it. it has now became my collection art pieces. when one day i could pass my GED, I will fix it and bring it back to life.
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Old Dec 10, 2012, 09:34 AM
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kentli22,
The problems new people have with glow or gasoline or model diesel engines go way back to the beginnings of the hobby. Although glow engines have some similarities with gasoline engines, the gas engines add some more complexity to the way one runs the engine and uses it. It just turns out that spark ignition gasoline engines are going to be more complicated than a glow engine is. But we still see numerous people having problems with glow engines too. So it isn't all that surprising.

Unfortunately, most gasoline engines are not really plug and play. One guy seems to have no problem with a particular brand engine and the next guy gets one too and has no end of problems with his engine. Even the high end, high quality brand name engines have had people that had problems with them. Usually not as often though.

Now this would apply to all engines but the NGH engines are test run at the factory, but the main needle setting is a little on the rich side. I haven't had to touch the low speed needle after my trials and tribulations with the first engine I used. So it is usually set pretty close. So normally one should be able to get it to run but on the rich side. But one common issue newbies tend to have is overcorrecting or making too large of a change to a needle or making too many changes at once. Do everything one at a time and make small changes, wait to see what happens and then make another small change. Try to avoid frantically tweaking everything in a attempt to get it to work. The factory test ran the engine so the settings are set pretty well to start with for you.

The other issues depend on the situation. I think the European folks were having less problems as some of their forums were showing threads and discussions about the engines and that they were working OK for them. So maybe it is our USA non-metric stuff that is causing some problems, along with our gasolines too.

Years ago, I used to get engines from other folks who said they were bad or junk or no bood, et cetera. I would check the engine out, set the needles back to default settings, then fire up the engine and run it, make some adjustments and then put the engine on a plane and have it flying Ok the next time I took the plane out to the flying field. So sometimes it is just people not understanding or developing a feel yet for using a glow engine, or gas engine or model diesel engine. Actually we can see the same thing with electric planes too, where people have no end of trouble trying to figure out what prop to use, what ESC, what battery, what size plane et cetera is needed for a particular electric motor.
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Last edited by earlwb; Dec 10, 2012 at 09:43 AM. Reason: correct typos and misspellings
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Old Dec 10, 2012, 10:34 AM
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Originally Posted by Nav_Aids View Post
I think the low price that Hobby King is charging has more to do with others dropping the GT9 than it's problems. Hobby King isn't playing fair in my opinion and is hurting the other distributors. With this motor I'd rather pay more just to get the after sales service.

Ray
Hi there Ray from this side of the fence H.K. didnt pickup this engine until after everyone else started dropping it ! Not the other way around . Cheers the pope
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Old Dec 10, 2012, 12:26 PM
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You guys simply don't understand distributors.

A distributor wants to be the one and the only, within the largest area he can occupy.
And in today's 'Global Village' reality, it might as well be the whole world.

One distributor doesn't 'rub shoulders' with another, unless it is for the purpose of 'taking him out'.

Even though HobbyKing is in Hong Kong, it is the American Way that he's playing...

Monopoly...
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