starfire73

I bought a GMS 47 on eBay, looks to be in great shape - almost brand new. No matter what I do, I can't seem to get it tuned so that it doesn't dead stick. I don't have a manual either.

- What is the factory setting for the low speed needle?

- I have tried the pinch test on the low speed needle, and high speed needle, and they seem to be set right.

- The engine wants to die when I go to full throttle. This doesn't happen during transition to full throttle, it happens after transition to full throttle - so I'm not thinking it's my low speed needle.

- I have tried stepping the high speed in and out, and can't seem to find the spot.

- I've checked for air leaks in the system and can't find any, no obvious bubbles in the fuel supply tubing.

- I've had it tuned where it ran up to full throttle and ran there for 30 seconds or so, then it just dies.

- I have tried two different glow plugs with no change.

...any ideas would be most helpfull.

w8ye

My Feedback: (16)

On the old ones I liked to have the low speed needle outside the spray bar about .020" when the throttle was wide open

You may have a bad fuel problem?

Wayne Miller

Hi,

There is a very large thread on the GMS 47 and trying to get it tuned. In the end, it was found there was a problem with the fuel intake hole needed to be drilled out. The thread also has suggestions for tuning. The following is the link to the thread, hope this helps.

http://www.rcuniverse.com/forum/m_22...tm.htm#2290854

Fly4Fun,

Wayne

aerofly0610

<pre>From
http://www3.towerhobbies.com/cgi-bin...?&I=LXDXM2&P=0


Factory Settings:
High speed: 1½ turns OUT
Low end: 2mm gap

I have one and love it, just watch the head,, the metal is a bit soft and the glow socket strips easy.
</pre>

Steve Percifield

My Feedback: (14)

Also, back when INDY RC was still in business. Jim Goad trold me one day, that most of the running problems with the GMS engines was a result of flyers using the wrong fuel. The engines were designed to run on very little or no Nitro. BTW, the "G" in GMS comes from Goad, he was one of the designers, so I assume he knew what he was talking about.

also, w8ye.... I see your note about your original AMA number. Mine is 31487... you beat me a week or so.

starfire73

Ok, I'll try the gap at .020" That sounds a little better then the 2mm gap they show on the Tower website. It must be a typo, because it's impossible to back the spray bar out 2mm.

w8ye

My Feedback: (16)

be sure and try your fuel in another engine to make sure that the fuel is not your problem. Fuel that has seen too much light will run the same was as you describe.

TimBle

GMS= Gemtec Machinary Systems..... where does Goad come from...?

Low speed setting is 0.2mm gap between spray bar and needle with the throttle fully open. Theres a typo on the Tower website.
High speed setting is 2 turns out.

the engine is design to run on 10% nitro methanol fuel and a wood prop is recommended, especially for running in.

I have had issues with this engine on Model Technics GoGlo 5% - could have been a bad batch. It runs perfectly on Morgans Omega 10%.
it seems to like a lower, less viscous oil content with a bit of castor.

My current settings is low speed at the factory setting - 10minutes
high speed at 1and 3/4 turns. Still rich so 1&1/2 turns could be good for post run in period.

screems fly me to the moon, past jupiter and mars. I call it Frank as a result.

I have another i am running in on a Cross 46A airframe. at factory settings it is delightfully responsive to the throttle and winds up like an F1 engine

w8ye

My Feedback: (16)

.2mm = .008"

starfire73

I found a thread that explained my problem.

http://www.rcuniverse.com/forum/m_96..._1/key_/tm.htm

I took the fuel inlet nipple off of the carb, and low an' behold - there was my problem. The hole in the spray bar did not correctly line up with the inlet hole. I had to drill it out. It died on fuel throttle because of the fuel constriction.