DBono99

My Feedback: (1)

Hi Everyone I was thinking of buying a GMS 47..Butr lately I hear that they have problems.. I have 2 of there 47's that are maybe 4-5 yo's.. Had some problems with them(Main Needle valve), but they seem to work fine. I rerad now about the carb. being misalinged? Any thoughts or suggestions will be welcomed.

Thanks Dan

Ed_Moorman

My Feedback: (1)

I also have 2 and have not had any problems. I do use the normal, front needle valve because I think a lot of problems come from leaks in the remote needle assembly.

I took one of the carbs off and unscrewed the fuel nipple and the hole in the brass jet tube was slightly off center. I used a couple of pieces of plywood and a vice to press the brass out, re-aligned it and tapped it back in with a short piece of dowel that I drilled out so it would fit over the jet tube. It doesn't seem to make any difference.

You can get a whole new carb body for $8, as I recall. I bought one just to check and it wasn't aligned much better than mine was so I am keeping it in reserve.

If your engines are running well, don't buy any trouble by messing with them. I think it's a good engine and my 2 were on a twin are going on a new twin.

RC-Captain

DBono99 let me guess ? Hackensack flyers .

Flyboy Dave

My Feedback: (21)

Aside from that fuel inlet misalignment problem, the GMS engine seems
to be a good engine....they sure put out the power.

FBD.

Flyer Freq

One of the problems with forums is that yesterdays information stays there for the world to see for a very long time. I have looked at several spray bars over the last year, and have not seen any more with the problems we have been discussing on another thread. I would say that the manufacturing issue took place about 2 years ago. I would really be surprised if anyone purchasing the engine today would get one with the bar problem. When you say that the carb body that was just purchased does not have the hole in the nipple aligned with the hole in the spray bar, you are correct. There is a hollow or undercut in the carb body that allows the hole to actually be turned away from you without affecting operation. The alignment problem that was causing an issue was that the spray bar hole was actually too far back in the direction of the needle valve. If the spray bar was rotated in a direction where the whole was easy to see, 1/3 to 1/2 of the hole was obscured do to the aluminum carb body. Fuel actually had to come through the nipple, take a right turn to go though the obscurred hole and in a thousandth of an inch turn back left to go through the orifice created by the needle valve and the spray bar hole.

It is my belief, and I know others on this sight that believe it too, that MECOA is aware of the manufacturing problem, and it has been corrected quite some time ago. Go ahead, buy another GMS .47 and have a good time. And for even more pleasure, try the .47 with a uniflo tank. Wayne put a link to a great site explaining the operation and assembly. Waynes thread is entitled GMS Tuning Problem. A lot of work has gone into that thread. You will not find better information on the .47.

Andy

GBR2

My Feedback: (1)

I have one of the 47's and they put out a lot of power but it also had a bad airleak. So sealed up the rear cover, between the carb and engine body, fuel nipple and spray bar. As I understand it there is also a possible front bearing leak in about 20% of the engines. The first thing I noted when I opened the box was a piece of paper telling me that if I fully close the throttle barrel and the engine doesn't stop, this is not a defect. I guess air leaks aren't defects. In any case, got the engine running alright eventually but you still can't kill it by closing the throttle barrel. Only engine that I've ever seen do that.

Flyer Freq

Don't take this wrong, but there is no such thing as an air leak in the front bearing in this style of engine. Without the leak in the bearing, the engine will not run right. I have done extensive testing with leaks in this engine. You would be surprised how tight it really is. Change the O-ring on the neack of the carb, and check to see if there is one where the carb slides into the crankcase. If there is, change it. You can get the right sized ring at any hardware store. When you mount the carb, hold the carb in tight and snug the jam bolt. I would really be surprised if the failure to shut down isn't solved. Again, all these solutions are on Wayne's thread. I hate to rehash them here.

Andy

Spicoli

Flyer Freq,

There is an airleak issue with that engine in the front bearing area. I have fixed one and my friend fixed one filling the fuel return passage.I posted the article by Dave Gierke in Wayne's post on how to fix it.Others have fixed it with a double sealed bearing.
I don't think you have done enough testing.

Flyer Freq

Spicoli:

I respectfully disagree, and mean no malice in saying this. If a sealed bearing is used in replacement of the unsealed bearing, the engine will not function as designed. The open bearing design allows fuel to flow to the front bearing to lubricate it. If the bearing is sealed, the fuel will not reach the return passage. If it did, the sealed bearing will create a vacuum at the bearing, and fuel will not be allowed to return. The engine may function for a while this way, but not for long. I don't remember for sure, but I believe this information was/is on the MECOA website(I have not been on there in a while). I think I also read about it in one of the engine discussions in one of the R/C mags, likely Model Aviation. My good engine leaks a small amount of fuel, and leaks air like a screen door, yet it turns an 11X3 APC at 16,000 RPM and a 12 1/4X3 3/4 APC at 12,100 RPM and behaves well. My friends engine leaks the same way, but once we changed the spray bar and the large O-rings around the carb, the bad behavior went away. It remains consitant in a hover and shuts off on command. Again, I don't mean any disrespect, but the front bearing air leak belongs on SNOPES. RC Universe is a valuable asset, but a lot of fiction gets backed up as fact and is there for everyone to see for a long time. If I had not checked this one out myself, I would believe as you do. It is because I believed it that I did my own testing and further research to prove it correct; I could not.

Andy

Wayne Miller

Hi,

I think that for the price you can not beat the GMS .47 engine when it is working right. I think the problems have been corrected in the newer GMS engines, however, if you happen across a problem engine, it is easily fixed and it is described in another thread. Since the price of the GMS is about, or less, than an OS, it is a very cost effective purchase.

You may want to check out the following thread. A lot of modelers grouped together to isolate the problem, and if you read the whole thread, you'll see what has been tried, what has worked and the final results, including tuning, modification, tanks etc. It is a good read if you want to understand this engine better. Any input you can give, is greatly appreciated.

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

Fly4Fun,

Wayne Miller
Pres. K/W Flying Dutchmen
MAAC 6166