GMS 120 ???
11-02-2008, 08:56 PM
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GMS 120 ???
Own a GMS 120. Does anyone know what 3D prop to use. I have it own a CG Wild Stik 120.
Also, has anyone found this engine needing a fuel pump. I'm not sure why, but it cuts out at times. It does on the stand and in the air. It's a very picky engine to adjust.[:@]
Also, has anyone found this engine needing a fuel pump. I'm not sure why, but it cuts out at times. It does on the stand and in the air. It's a very picky engine to adjust.[:@]
11-03-2008, 12:05 AM
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RE: GMS 120 ???
Have you tried tapping into your exhaust (muffler) and running a line to your tank for pressure? While on the stand you might also try mounting the fuel tank above the carb to see if that makes it run more consistantly before doing anything. I would think that tapping into your exhaust would be less expensive than a fuel pump.
Bill
Bill
11-03-2008, 11:40 AM
#3
RE: GMS 120 ???
You might give this a read. You are not the first to struggle with this engine once it is in the air.
http://www.rcuniverse.com/forum/m_55...tm.htm#5589708
I'd be inclined save the funds a pump would cost and look at a Thunder Tiger Pro 1.20 carb. They are cheep and well liked.
http://www.thundertiger4u.com/carbur...0-p-12708.html
Bill
http://www.rcuniverse.com/forum/m_55...tm.htm#5589708
I'd be inclined save the funds a pump would cost and look at a Thunder Tiger Pro 1.20 carb. They are cheep and well liked.
http://www.thundertiger4u.com/carbur...0-p-12708.html
Bill
11-03-2008, 04:10 PM
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RE: GMS 120 ???
I have a stock muffler that w/ a factory exhaust tap. I have a Perry Pump installed and have tapped engine case already...will try this set-up tomorrow at club field. I'll do further tweeking of carb then. I'm not giving up on this engine. Perry Pump.com sells a carb to fit this engine to be used along w/ a Perry pump ($48.50 + shipping). My tank is installed under wing of plane @ CG. That's part of the reason I need a pump. My Cap-X w/ a OS 160 was set-up this way and it ran great. My OS 160 had somewhat of the same problems this engine has, which is it runs rich @ midrange in air and wuold dead stick until pump was installed. If all else fails...get another carb.
11-03-2008, 05:59 PM
#5
RE: GMS 120 ???
I have a GMS 1.20 and will be very interested in what progress you find. Currently it is not installed in anything so I would be able to lend much practical help. I personally have never had much luck with Perry/Varisane (sp?) pumps but will be waiting to see how your install goes.
I have had very good luck with Bill Cline's regulators... Provided the carb is not too large to begin with. http://www.billsroom.com/pcfs/fuelsysdesc.htm
Bill
I have had very good luck with Bill Cline's regulators... Provided the carb is not too large to begin with. http://www.billsroom.com/pcfs/fuelsysdesc.htm
Bill
11-05-2008, 11:17 AM
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RE: GMS 120 ???
Has anyone put a different carb on this engine with success. I keep hearing people talk about it, but has anyone did it & had success afterwards...Please tell me.
Yesterday I patiently spent time trying to tune this engine. I know that one afternoon may not be enough effort, but I well say this, I have found that the only way to keep this engine performing w/o dying is to strap a glow plug drive to it. I actualy agree with the thread, don't remeber who posted it, that said it may be a lack of fuel between to carb & spark maybe due to sucking air from somewhere. The Perry Pump did it's job, but I think once it leaves the carb, ITS A DEAD ISSUE.
I tried many settings both rich & lean. The one thing I did find is this engine runs a lot better on the lean side with a very hot plug, OS F or A3. I was able to fly one time, steep inclines, descents & a loop or two, about, 5 minutes before it died on approach.
I set the low end to nearly non-existing, just before it makes that lean engine tune, which is a long transition down to low throttle. It seems to run longer times in the air with this setting. Just don't throttle down below half until your on approach. I made two more flights and it did just find as long as I was above half throttle. Of cousre it died on approach each time.
Is that crazy or what.
Yesterday I patiently spent time trying to tune this engine. I know that one afternoon may not be enough effort, but I well say this, I have found that the only way to keep this engine performing w/o dying is to strap a glow plug drive to it. I actualy agree with the thread, don't remeber who posted it, that said it may be a lack of fuel between to carb & spark maybe due to sucking air from somewhere. The Perry Pump did it's job, but I think once it leaves the carb, ITS A DEAD ISSUE.
I tried many settings both rich & lean. The one thing I did find is this engine runs a lot better on the lean side with a very hot plug, OS F or A3. I was able to fly one time, steep inclines, descents & a loop or two, about, 5 minutes before it died on approach.
I set the low end to nearly non-existing, just before it makes that lean engine tune, which is a long transition down to low throttle. It seems to run longer times in the air with this setting. Just don't throttle down below half until your on approach. I made two more flights and it did just find as long as I was above half throttle. Of cousre it died on approach each time.
Is that crazy or what.
11-10-2008, 05:20 AM
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RE: GMS 120 ???
I ask if anyone has had any success using another carb & what kind? Please respond.
I knew better then to do this, but just out of curiosity, I called Great Planes warranty/Service tech dept to ask about past & reecent issues related to this engine. And out of my amazement, this so called tech simply said that I was the first person to ever call about any issue on this engine. I told this tech that he either lives on a another planet or, in so many words, he's the perfect yes boy for Great Planes.
Like I said, I knew better then call GP/Tech dept. I'm a glutton for punishment
I have spent $$$$ from Great Planes/Tower and have found out on many occassions they seem to ignore problems they can't explane.
I would hate to know that the all mighty dollar is all they're concerned about LOL.
I knew better then to do this, but just out of curiosity, I called Great Planes warranty/Service tech dept to ask about past & reecent issues related to this engine. And out of my amazement, this so called tech simply said that I was the first person to ever call about any issue on this engine. I told this tech that he either lives on a another planet or, in so many words, he's the perfect yes boy for Great Planes.
Like I said, I knew better then call GP/Tech dept. I'm a glutton for punishment
I have spent $$$$ from Great Planes/Tower and have found out on many occassions they seem to ignore problems they can't explane.
I would hate to know that the all mighty dollar is all they're concerned about LOL.
11-10-2008, 11:07 AM
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RE: GMS 120 ???
The big thing, is what RPM are you trying to run at? Many, many people just flat out put too much propeller on an engine and then wonder why they have problems. Also, big engines need big fuel tubing or they won't get good fuel draw. People started to learn this when the O.S. Max BGX-1 3500 came out. The 120-size two-stroke engines are no exception. You'll need larger tubing from the clunk in the tank all the way to the carb, and on the muffler-pressure line. You'll need to wire-tie the tubing in place because it won't hold itself onto the fuel fittings.
Nowhere do you say what propeller or fuel you are trying to use.
When tuning the carb, you must start out with an excessively-rich low-speed needle setting. Start at part throttle and get the high-speed mixture tuned first. Once the high-speed mixture is properly-tuned, only then can you start to work on the idle mixture. If you don't get it done this way, then finding the proper balance between the needles will be problematic.
Prop the engine for somewhere between 10,000 and 11,000 RPM when leaned to just rich of peak RPM on the ground. A prop that turns this RPM and flies your airplane as desired is the "correct" propeller. All propellers listed in the manual are only suggestions. You have to "play" with different props to see what ones will work.
Nowhere do you say what propeller or fuel you are trying to use.
When tuning the carb, you must start out with an excessively-rich low-speed needle setting. Start at part throttle and get the high-speed mixture tuned first. Once the high-speed mixture is properly-tuned, only then can you start to work on the idle mixture. If you don't get it done this way, then finding the proper balance between the needles will be problematic.
Prop the engine for somewhere between 10,000 and 11,000 RPM when leaned to just rich of peak RPM on the ground. A prop that turns this RPM and flies your airplane as desired is the "correct" propeller. All propellers listed in the manual are only suggestions. You have to "play" with different props to see what ones will work.
11-10-2008, 01:21 PM
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RE: GMS 120 ???
Dude, I must of stuck one of your nerves. I'm sorry if I did so, but I'm the customer. Futhermore I have years of tuning thse small engines. No one seems to care if we, the CUSTOMER who spends the money so that YOU can keep a job, pain stakily spends hard earned money trying to tune CRAP!!!
I HAVE TRIED TUNING THIS ENGINE ACCORDING TO FACT SPECS. DO US ALL A FAVOR, SPEND TIME WORKING OUT THE KNKS BEFORE SELLING THE CRAP.
INSTEAD YOU ARE DOWN GRADING THE CUSTOMER WHO MIGHT KNOW JUST LITTLE ABOUT TUNING,
APPARENTLY YOU HAVEN'T TUNED ONE OF THESE ENGINE, BECAUSE I WOULD LOVVE TO SEE THE ONE YOU HAVE CURED.
JUST FIX THEM BEFORE YOU SALE THEM!!!!!!
I HAVE TRIED TUNING THIS ENGINE ACCORDING TO FACT SPECS. DO US ALL A FAVOR, SPEND TIME WORKING OUT THE KNKS BEFORE SELLING THE CRAP.
INSTEAD YOU ARE DOWN GRADING THE CUSTOMER WHO MIGHT KNOW JUST LITTLE ABOUT TUNING,
APPARENTLY YOU HAVEN'T TUNED ONE OF THESE ENGINE, BECAUSE I WOULD LOVVE TO SEE THE ONE YOU HAVE CURED.
JUST FIX THEM BEFORE YOU SALE THEM!!!!!!
11-10-2008, 01:37 PM
#11
RE: GMS 120 ???
Geez
First thing that comes to mind is the fact that you are tuning the engine and have a pump. I found this to be a bit difficult with my first pump. The symptoms you are describing are leading me to believe that you have the pump delivering too much fuel, and hence your low mixture is almost closed and the engine wants to die without a glow driver installed.
The best thing to do is to break in and tune the engine without the pump. Get your needle/mixture settings adjusted properly, then tune the pump to the properly adjusted needle settings.
Second thing - Fatboy, maybe you got a 'bad one'. Nothing is perfect in this world. I spent the extra $$$ and got a 120AX, and there was a slight imperfection in the manufacturing which caused some problems. I sent it to Hobby Services and had a brand new engine within one week, now which is performing flawlessly.
Bax has a lot of experience with these things and is trying to help you enjoy your product. I don't see the need to scream at him. You also have drilled into the engine and have added an aftermarket part, so you have taken some of the responsibility off of the manufacturers hands. Many manufacturers would say that you have voided the warranty. Hobby Services won't do that, so be thankful.
I'm not a gambling man, but I would bet on this one that it is a pump issue or a fuel system issue, and not a problem with the engine at all.
Edit Just want to point out that the fuel tank would need to be moved back to the firewall if you remove the pump and re-tune the engine. Maybe it's a pain but it's the right thing to do and is worth it in the end.
First thing that comes to mind is the fact that you are tuning the engine and have a pump. I found this to be a bit difficult with my first pump. The symptoms you are describing are leading me to believe that you have the pump delivering too much fuel, and hence your low mixture is almost closed and the engine wants to die without a glow driver installed.
The best thing to do is to break in and tune the engine without the pump. Get your needle/mixture settings adjusted properly, then tune the pump to the properly adjusted needle settings.
Second thing - Fatboy, maybe you got a 'bad one'. Nothing is perfect in this world. I spent the extra $$$ and got a 120AX, and there was a slight imperfection in the manufacturing which caused some problems. I sent it to Hobby Services and had a brand new engine within one week, now which is performing flawlessly.
Bax has a lot of experience with these things and is trying to help you enjoy your product. I don't see the need to scream at him. You also have drilled into the engine and have added an aftermarket part, so you have taken some of the responsibility off of the manufacturers hands. Many manufacturers would say that you have voided the warranty. Hobby Services won't do that, so be thankful.
I'm not a gambling man, but I would bet on this one that it is a pump issue or a fuel system issue, and not a problem with the engine at all.
Edit Just want to point out that the fuel tank would need to be moved back to the firewall if you remove the pump and re-tune the engine. Maybe it's a pain but it's the right thing to do and is worth it in the end.
11-10-2008, 03:03 PM
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RE: GMS 120 ???
Geeez[&o]
Have you guys read any of these threads related to the GMS 120. Look, please believe me when I say I have tried EVERYTHING;
On the test stand before mounting...On the plane w/ & w/o the perry pump, ajusting for hours...moving the tank. It would get close but NO LUCK!! IT'S THE CARB.
Mecoa has hundreds of GMS 120 engines at their Dist. & Factory Co in CA w/o carbs because they sold them to hundreds Great Plane customers who bought GMS 120 engines with sorry #@!%&# remote needles & carbs.
The GMS 120 engines sold @ Mecoa had very very little or no problems. You know why, because they tested & fixed them before they sold them. I bought several GMS engines from Mecoca w/o any problems.
Mecoa did this because they felt for the customer & because of the compamy's size they could not afford selling the GMS line of engines w/o doing so. Isn't that so easy.
I know GP can do this.
Have you guys read any of these threads related to the GMS 120. Look, please believe me when I say I have tried EVERYTHING;
On the test stand before mounting...On the plane w/ & w/o the perry pump, ajusting for hours...moving the tank. It would get close but NO LUCK!! IT'S THE CARB.
Mecoa has hundreds of GMS 120 engines at their Dist. & Factory Co in CA w/o carbs because they sold them to hundreds Great Plane customers who bought GMS 120 engines with sorry #@!%&# remote needles & carbs.
The GMS 120 engines sold @ Mecoa had very very little or no problems. You know why, because they tested & fixed them before they sold them. I bought several GMS engines from Mecoca w/o any problems.
Mecoa did this because they felt for the customer & because of the compamy's size they could not afford selling the GMS line of engines w/o doing so. Isn't that so easy.
I know GP can do this.
11-11-2008, 04:58 AM
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RE: GMS 120 ???
Fatboy, regardless of what people are going to tell you, the GMS 1.20 is a hit and miss proposition when it comes to carburetion.
I have worked on one that, no matter what we did with it (a selection of glow plugs, low and high speed needle settings, fuel, nitro percentages, propellors from 16 x 10s down to 14 x 8s, full moon, Saturn and Jupiter alignment with Mercury, snake oil, magnetic bed underlays, divining rods and morris dancing) we could not prevent a very rich mid range which caused stutters and flame-outs with anything except the OS Type F plug (which reduced the tendency to flame out but still stuttered like all buggery at part throttle).
It was simply a case of bad carburettor metering. This happens with carbs that are assembled with less than optimal quality control - some are just bad whereas the odd one can be OK.
The example I set up and broke in for a guy would definitely have benefitted from fitment of another carb - the OS 7D is one that springs to mind.
Unfortunately, the engine I was involved with was removed by the owner and consigned to a lonely life as a paper weight before we got a chance to try out re-carbing it.
Buy an OS 1.20 AX and stop wasting any more of your remaining life on this problem.
I have worked on one that, no matter what we did with it (a selection of glow plugs, low and high speed needle settings, fuel, nitro percentages, propellors from 16 x 10s down to 14 x 8s, full moon, Saturn and Jupiter alignment with Mercury, snake oil, magnetic bed underlays, divining rods and morris dancing) we could not prevent a very rich mid range which caused stutters and flame-outs with anything except the OS Type F plug (which reduced the tendency to flame out but still stuttered like all buggery at part throttle).
It was simply a case of bad carburettor metering. This happens with carbs that are assembled with less than optimal quality control - some are just bad whereas the odd one can be OK.
The example I set up and broke in for a guy would definitely have benefitted from fitment of another carb - the OS 7D is one that springs to mind.
Unfortunately, the engine I was involved with was removed by the owner and consigned to a lonely life as a paper weight before we got a chance to try out re-carbing it.
Buy an OS 1.20 AX and stop wasting any more of your remaining life on this problem.
11-11-2008, 10:05 AM
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RE: GMS 120 ???
I already made up my mine to fine another carb. Like I said, I'll not give up on this engine. You know curiosity killed the cat.[>:]
11-11-2008, 10:48 AM
#15
RE: GMS 120 ???
I already made up my mine to fine another carb. Like I said, I'll not give up on this engine.
Fatboy, regardless of what people are going to tell you, the GMS 1.20 is a hit and miss proposition when it comes to carburetion.
Buy an OS 1.20 AX and stop wasting any more of your remaining life on this problem.
Bill
11-12-2008, 03:27 PM
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RE: GMS 120 ???
Yes Sir, I read that thread, so why did buy a TT carb. Is there anything wrong w/ the Mecoa carb. If not, then let's talk up a deal.
01-25-2009, 06:20 PM
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RE: GMS 120 ???
Hello,
I have a GMS 120 engine and have a question regarding the factory carb that comes with the engine. The engine is running rich on the low end. Top end is fine. I have slowly turned the low end screw clockwise to lean it out. It has improved but to my amazement the low end screw is now turned in as far as it will go and its still running rich?? Whats up with this? That screw adjust fuel mixture correct?Therefore you would turn it clockwise to lean it out. Is that correct? It is not like the old carbs that controls air flow from that screw.
Can someone confirm this? Do I need to just get another carb like the Tunder Tiger or the KAVAN that Mecora sells. Anyone have tried these carbs or suggest another one.
Thanks for any help. Roy
I have a GMS 120 engine and have a question regarding the factory carb that comes with the engine. The engine is running rich on the low end. Top end is fine. I have slowly turned the low end screw clockwise to lean it out. It has improved but to my amazement the low end screw is now turned in as far as it will go and its still running rich?? Whats up with this? That screw adjust fuel mixture correct?Therefore you would turn it clockwise to lean it out. Is that correct? It is not like the old carbs that controls air flow from that screw.
Can someone confirm this? Do I need to just get another carb like the Tunder Tiger or the KAVAN that Mecora sells. Anyone have tried these carbs or suggest another one.
Thanks for any help. Roy
01-26-2009, 03:09 PM
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RE: GMS 120 ???
Hello,
I have this GMS 120 engine I bought on E-Bay. Please review the pics but I am not sure this is a GMS carb on it. It has no marking on it like the GMS carbs. Futhermore it does not run right. Even with the low end screwed all the way in it still runs rich. I put on an old OS Max 7L carb on it and now it runs great. Turns a 16X6 at 9,500 rpm.The carb base outer diameter has a 15mm . Please advise, Roy
CAN ANYBODY IDENTIFY THIS CARB IN THE PICS? THERE IS NO NAME OR MARKINGS ON IT. CAME OFF A USED GMS 120 I BOUGHT
I have this GMS 120 engine I bought on E-Bay. Please review the pics but I am not sure this is a GMS carb on it. It has no marking on it like the GMS carbs. Futhermore it does not run right. Even with the low end screwed all the way in it still runs rich. I put on an old OS Max 7L carb on it and now it runs great. Turns a 16X6 at 9,500 rpm.The carb base outer diameter has a 15mm . Please advise, Roy
CAN ANYBODY IDENTIFY THIS CARB IN THE PICS? THERE IS NO NAME OR MARKINGS ON IT. CAME OFF A USED GMS 120 I BOUGHT
01-26-2009, 04:16 PM
#20
RE: GMS 120 ???
It looks like Mecoa is using Kavan carburetors on thier GMS 120's
https://shop.mecoa.com/shopdisplayproducts.asp?id=80#
Opps, sorry rdawson...
https://shop.mecoa.com/shopdisplayproducts.asp?id=80#
Opps, sorry rdawson...
02-07-2009, 11:27 AM
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RE: GMS 120 ???
Hello,
I have a GMS 120 with the Kavan carb on it. On the carb it has 2 intakes on it. One is for the main fuel with needle valve and the other is for what? What do I connect it to. I have never seen this setup on a carb. I cant get the motor to run. It has the old style air screw for low end. Does anyone know what the starting point it for the air screw adjustment? Also what do I connect the other connection on the carb. Is that muffler pressure or fuel. Please advise, Thanks
I have a GMS 120 with the Kavan carb on it. On the carb it has 2 intakes on it. One is for the main fuel with needle valve and the other is for what? What do I connect it to. I have never seen this setup on a carb. I cant get the motor to run. It has the old style air screw for low end. Does anyone know what the starting point it for the air screw adjustment? Also what do I connect the other connection on the carb. Is that muffler pressure or fuel. Please advise, Thanks
06-28-2009, 12:12 PM
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RE: GMS 120 ???
After finding this thread and owning a GMS 120 for over a year now trying everything as others have done i replaced the carb with the thunder tiger 120 one mentioned in this thread and still have the same issues it seems to run better yes but it wont get off the ground it flames out wheni go to throttle up for take off. The enigne i have is on a BIg stick and has a 16X6 prop on it. the plane has flown withthis combo already. I have video.
But now i cant seem to get it off the ground a fellow RC'er that has much more experince sujested opening the exahust port up more not a lot just a little to prevent the rich running condition. but since i replaced the carb it doesnt seem to be running rich but goes blah on take off and flames out but seems to transition fine sitting on the stand running it up before take off and all seems normal then go for the take off and throttle up and it goes blah and dies what a strange engine. i have a MAC muffler on it i ordered special for it since the pitts muffler didnt allow enough back pressure i have now spent to much on this i couldhave had a really good OS 160 FX.
Isnt it strange how the rc bug is I have been fifddling with this engine for about a year now i'm thinking about taking drastic measure and changing the port timing to see if it will work. and if not then i think i will make it a Geocache First to find for someone else to tinker with.[link=http://www.youtube.com/watch?v=gCWHY4ja3qA]BIG STICK GMS 120 VIdeo[/link]
But now i cant seem to get it off the ground a fellow RC'er that has much more experince sujested opening the exahust port up more not a lot just a little to prevent the rich running condition. but since i replaced the carb it doesnt seem to be running rich but goes blah on take off and flames out but seems to transition fine sitting on the stand running it up before take off and all seems normal then go for the take off and throttle up and it goes blah and dies what a strange engine. i have a MAC muffler on it i ordered special for it since the pitts muffler didnt allow enough back pressure i have now spent to much on this i couldhave had a really good OS 160 FX.
Isnt it strange how the rc bug is I have been fifddling with this engine for about a year now i'm thinking about taking drastic measure and changing the port timing to see if it will work. and if not then i think i will make it a Geocache First to find for someone else to tinker with.
[link=http://www.youtube.com/watch?v=gCWHY4ja3qA]BIG STICK GMS 120 VIdeo[/link]
03-01-2012, 05:34 AM
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RE: GMS 120 ???
In the category of better late than never... Answer: The carburetor picured in the post by rdawson (see Post #:19 above) that's the carb that came as a stock item on the GMS 1.20 before the Mecoa guys started using the Kavan carb.
03-04-2012, 04:10 PM
#25
RE: GMS 120 ???
The two GMS 1.20 engines I have had bad carbs and remote needle valve units on them. The needle valve unit was allowing a lot of gas bubbles to form and had false needle settings. I replace the carb and remote needle valve unit with a Perry carb and then the engines behaved quite well.
A Webra 1.20 muffler fits it quite good too. But I am using a Bison Sport Muffler for a Webra 1.20 on the engine. In hindsight, the GMS carb may be OK if you use a better remote needle valve unit on it. But I haven't tried it yet myself, since the Perry Carb worked good, I didn't bother persuing it any further. I did find the engines preferred running more on the rich side than you might think. If you tried to lean them out a little more, they had a tendency to just quit on me for no reason. This might be why they suddenly just quit in the air on people. The fuel tank starts getting lower on fuel level and the engine leans out a little more and goes over the edge, so to speak, and suddenly dies onin flight. But if I left the engine running more on the rich side, they behaved well then. I also think they do not like rev'ing up all that high too, maybe RPMs around 8,000 RPMs is tops for them.
I acquired my two examples from people who where totally frustrated with them and they gave up in disgust with them.
[
A Webra 1.20 muffler fits it quite good too. But I am using a Bison Sport Muffler for a Webra 1.20 on the engine. In hindsight, the GMS carb may be OK if you use a better remote needle valve unit on it. But I haven't tried it yet myself, since the Perry Carb worked good, I didn't bother persuing it any further. I did find the engines preferred running more on the rich side than you might think. If you tried to lean them out a little more, they had a tendency to just quit on me for no reason. This might be why they suddenly just quit in the air on people. The fuel tank starts getting lower on fuel level and the engine leans out a little more and goes over the edge, so to speak, and suddenly dies onin flight. But if I left the engine running more on the rich side, they behaved well then. I also think they do not like rev'ing up all that high too, maybe RPMs around 8,000 RPMs is tops for them.
I acquired my two examples from people who where totally frustrated with them and they gave up in disgust with them.
[
