I had to edit my post above. I meant to say "this engine has a large muffler"....[sm=red_smile.gif]

FBD.

No kidding... it works.

The GMS/TH engines seem to develope enough of a vacuum that even with no pressure from the muffler straight up flight is not overly problematic.

When my muffler fell off I was doing aerobatics at a good distance from my position, so I did not hear the change in engine loudness.

I was performing straight up flight, inverted, etc. at a good height. I noticed almost no change in the flight characteristics.

Only when I brought it much closer in did I notice the rather loud sounds emanating from the front remaining muffler half.

I ended up making several more flights this way before leaving for the day.

I did note that the amount of leeway I had in the tuning dropped greatly, but it still worked.

Be careful, my Rossi 65 runs without muffler pressure also , and some times it flames out on take off. I think you are only getting lucky with a good prime as I did the last time I ran the Rossi 65 with out the back pressure hose to the tank.

I would never advocate running the engine this way...

The point is that with the GMS/TH engines muffler pressure is not as big of a factor as it is for other engines, ( within reason of course ) and that tuning problems usually revolve around something else.

I've recently purchased two GMS engines (the 40 remote needle and the 47 front needle) and I had to push out the spray bar in both carbs due to fuel hole misalignment and then reinstall them. Also these two engines of mine had to be set on the high speed needle first ( a couple of clicks rich) and then set the low speed needle so that when you pinch the fuel line at idle the rpms just barely rise then the engine will die. Remember to throttle up and clean out the engine between adjustments. This has worked on both my engines and they idle and throttle up with out any problems as well as they will fly perfect until the tank runs out. I am also using an OS a-5 plug, Omega 15% and the altitude is 4000 feet where I fly.

Thanks Don that was a very good explanation and right on the money.

ANY OF YOU GUYS KNOW WHAT IS THE FACTORY LOW SPEED NEEDLE SETTING OF THE GMS 47? I REMOVED IT TO CLEAN THE ENGINE FROM RESIDUES BEFORE OPERATING IT, BUT LOST THE NOTES I MADE ABOUT HOW MANY TURNS IT WAS SET.

THANKS FOR YOUR HELP.
RAFA

Fully open the throttle barrel look inside and turn the needle in until you can just fit a cover of a match package between the needle and the bar you will be very close.

cheers

Peter thanks for your help.

Rafa

Hi guys:

As I said I bought a brand new GMS47, I've put it apart to clean engine before break in, have read the entire thread about some engine problems, started break in with a 9/7 MA and omega 10% fuel, after two tanks flew my plane, engine performance was ok till it suddenly died fly after fly, there was obvious overheat cause it's a brand new engine.

Started thinking about drilling and all that stuff you mention, but surprise come out when I runed out of fuel ( omega 10% ) bought another brand cause it was only one in store ( cool power 10 % ) have to tell you, I played a bit with low speed needle and results where amazing, engine works outstanding with no need of drilling any part of it and screams like hell.

May be GMS has worked out the problem on carb or I was just lucky with mine, there is one thingh for sure all I did was to set idle neddle at 1 3/4 turns, thats where it ended up I like these engines no matter what other pilots say.

Regards.
Rafa

Rafa,


What 'drilling' are you talking about!?

I don't think a new engine needs any part 'drilled' to make it run properly...

Also, CoolPower (better known here as CruelPower ) is not the right fuel for this engine!
It needs fuel with a good measure of castor oil and the CP has none at all.

The manufacturer tells you so [link=http://www.morganfuel.com/omega_main.htm]specifically[/link] that 'Omega' is the right fuel for ABC/ABN engines.

It is more than likely that either; 1. your engine 'matured' to just beyond break-in during that last flight, or 2. the previous gallon of Omega was old/stale/absorbed moisture and this is what gave you those troubles.


I hope you did the break-in as described [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]here[/link].

...some of the early GMS carbs (like mine) were miss-drilled for the inlet of fuel aprox.
40% restriction. This lead to a leaning out in flight, and deadstick. Most of them would
not respond to the main needle....you could open them up 7-8 turns and nothing would
happen due to the restriction. In other words, you could not get them richened up enough
flight. The problem was, they would run OK on the ground with the richness just enough to
deceive the operator into believing the engine was running OK. Then after a minute in the air
the inevitable leaning out, overheating, and dead stick.

Also the muffler nipple was restricted. This caused a loos of fuek pressure that exasperated
the problem. I went through my engine with a fine tooth comb before I ran it, because of
the problems others were having, and I isolated these two problems.

Enlarge this pic and see the restriction. Mine runs like a top. No doubt it would have run
poorly with these obvious problems.

FBD.

Thank you for the insight, Dave.

It is hard to believe such defective merchandise could reach the market in large numbers...

Dar,

It happens with full sized engines too. There are cases of Allison turbines having defective compressor blades, and rebuild plants making mistakes during rebuild. We have heard of QC problems with model engines often enough too.

Barry,


Maybe this is one reason Rolls-Royce (UK) [link=http://en.wikipedia.org/wiki/Rolls-Royce_plc]now owns[/link] Allison Turbines... To get all the bugs out...

I have several friends that work at Rolls-Royce ,AKA Allison Turbines............

The Allison problem was back in the 1970's, I think. It was an installation problem with a worker who introduced contamination. Very tough to track down. The rebuild issues were in S. Korea at an Army facility and not related to Allison. Sorry to hear they were bought out. I didn't know that.

I mentioned that to put our glow engine design and QC issues in perspective. A breakdown in the assembly process happens with almost all brands at one time or another.

Rolls Royce is a publically held English company. It has a 15% cap on any particular ownership but no aggregate limit on foreign investment as a whole.

They have many interests in the USA besides Allison. They also bought out Cooper Bessemer near where I live.

In reality, it is no different than any other public company in this country and no reason to think that quality control will be any better than it was before?

Everyday for months they have ads in the paper wanting the pretty much same specific skills. They must not pay much / or they are too cheap to culture these people themselves?

Dar: I did followed break in as they mention in their manual, if you havent read the entire thread, some pilots have had tuning problems with this engine, solution was to drill nipple on carb and muffler, spray bar and muffle hole just one size larger, but main problem was missalignment of carb nipple and spray bar holes.

Dont think CP will harm any engine if you add some castor oil to it, at least this engine is working like hell and that is what it was intented to do or what I wanted.

Regards.
Rafa

Rafa,


CP is already 17% all synthetic oil.

If you add 3% castor oil to it, you would have roughly 20% oil.


The Omega, as it comes, is 4.9% castor oil and 12.1% synthetic (break up 17% 30/70).

Why bother buying additional castor oil to add to CP, if you can have the castor oil pre-mixed in Omega?


Seeing the engine perform in the short-run has no bearing on the end result...
Both Morgan and OS say you should use castor oil in the fuel for ABC engines...

But hey, it's your engine and you can do whatever you want with it.

But hey, it's your engine and you can do whatever you want with it.

[/quote]


Your right my friend.

Let me tell you I've used CP since long time with OS and GMS engines with no harm to them , only difference you have is that castor will burn at higher temps than sinthetics but remember tech in sinthetics has improved much also.

There are opinions about the use of fuels like clouds in the sky, whats important is performance and seems, like my GMS likes CP better.

Hi,

I was very surprised when I stumbled upon this thread again. I replaced my computer and somehow I was not being notified of new postings. I thought the thread was dead!

I'm glad to see it is still going strong (since I started it) and people are getting the GMS's up and running!

Fly4Fun,

Wayne

Wayne it's still strong and coming up to help others run their GMS right, txs it was very helpfull for me.

I tought mine was ok because it was running fine, today I cheked the sprybar and carb nipple alignement and was surprised it was not ok, I drilled the hole on spraybar and nipple, hope it gets better.

Regards .
Rafa

Hi Alcarafa,

Let us know how it the modification works for you.

Fly4Fun,

Wayne Miller

Wayne....

....mine is still running like a top.

FBD.