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Old 09-24-2009, 04:33 PM   #1
Thunder Chicken
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GMS engines

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I was looking to buy a new os .25fx but noticed they are no longer available. A newer more expensive version is replacing it.
I was not really looking foward to spending that much on a .25 for combat.
Are the GMS pro engines any good? They are a lot cheaper than the os and thunder tiger were........too cheap.....????!!!!
I believe there is a magmum .28, but not sure how it fits into the ww2 combat rules.
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Old 09-24-2009, 05:15 PM   #2
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Re: GMS engines

My friend and I are both running GMS 47's, and they are very strong motors. Would not hesitate to go with more if required.

Couple of little pointers if our experience is any indication. Both have the notorious habit of continuing to run with the carb closed. We have tried different make carbs and have tamed that down a bit, but it never went away. I even replaced the stock throat O-Ring with a better version and doubled up with another thin one at the base of the carb body. Just got used to it.

They also need proper break in. At first ours had continuous dead sticks with approx half a tank remaining or better, (even slobbering rich at take off) but once they settled down proved to be reliable, if a bit on the thirsty side. That could be due to the carb changes.

What came in handy was that my OS 40FSR, 40SF and the 47 all shared the same bolt pattern, so it was simply a matter of 5 minutes work, resetting the throttle linkage and servo to run a different plant for comparison. It usually took longer to change the spinner over.
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Old 09-24-2009, 09:48 PM   #3
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Re: GMS engines

Hi TC,

We had the same problems with the early (2001) GMS.25s that Cougar449 had. And the old mufflers kept rattling off...

The newer GMS.25s with the R/N valve and the newer mufflers are much better, I hear over the internet. They are not quite as strong, and 1oz+ heavier than an OSFX.25.

Scuttlebut says that Magnum will be coming up with a new engine that will replace/match the OSFX.25 by Feb. 2010.

Some combat and .25 pylon racers are doing some GMS.25 comparative testing with the OSFX.25.
I'll post the links when they have done so.

The new OSAX.25 is more of a 'chugger' prop wise, but puts out just as much HP as an OSFX.25 at 1.5oz heavier. (the price of it MUST go down ! )

The stock Magnum.28 is almost on par with an OSFX.25 and 'technically' is not legal for Maac WW2 Scale Combat, but there is no CD I know of who would not let a Mag.28 fly unless it was outperforming a stock OSFX.25.

There are ALLOT of pilots wondering why OS dropped the OSFX.25.

If you don't mind 'fartin' around with engines, go with the GMS.25. I think the Magnum.28 is more proven. If you can wait, the next Magnum.25 should be worth waiting for...

It is great to hear of some interest in Maac Scale Combat from 'Up North' ! ! !

Take care,
Have fun,
Maac 6437
Unabashed Combat Team
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Old 09-24-2009, 10:10 PM   #4
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Re: GMS engines

My brother and I are running 3--.47s, 1--.61 and 2--.76s and they all run great. They take a bit longer to break in and come into there own, but when they do, a better motor for the price cannot be had. They have proven to be super reliable and deadsticks are a non issue. I can't remember the last time one quit on me in the air.
If money is no problem, you can go with an OS or another brand, but when the GMS can be had for about 2 for 1 over the others, I know which way I would go

Just my opinion


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Old 09-26-2009, 07:51 PM   #5
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Re: GMS engines

Try a google search! Not all GMS engines are created equal. There are three guys in our club that have GMS .40's and they are dogs, there are a couple of .47's and the newer model with the remote needle runs great. I am a professional mechanic with years of experience on two cycle engines. Now a days you need to do a lot more research, especially on the newer engines. Even some of the standard brands cannot be trusted.

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Old 09-27-2009, 05:03 PM   #6
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Re: GMS engines

i have bought four GMS's (three 47's and a .32). all have been reliable screamers. great value in my opinion. john
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Old 09-27-2009, 08:41 PM   #7
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Re: GMS engines

Last year I bought a GMS 76. need long break in. Tuning the carburetor for mid range and smooth transition is not easy. The Idle or low needle valve is controlling the idle, mid-range up to maximum speed. once you adjust the carburetor properly it runs OK but you have to be ready for dead stick landing all the time. engine keep running when the carburetor is fully closed on very low RPM.
It won't be my first choice specially for big and expensive planes

Last edited by bavl; 09-28-2009 at 09:26 PM.
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Old 10-02-2009, 07:53 PM   #8
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Re: GMS engines

Hi ThunderChicken,

Here is a link for replacements for the OSFX.25:

The GMS.25 (remote NV) might be OK.

Still waiting on news of a possible new Magnum.25 to replace the OSFX...

Take care,
Have fun,
Maac 6437
Unabashed Combat Team
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Old 10-16-2009, 04:24 PM   #9
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Re: GMS engines

I have a GMS 47 32 and 61 all are great engines
When nothing goes right..................Turn left

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Old 10-20-2009, 09:14 AM   #10
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Smile Re: GMS engines

Spend the extra $$$$ and get an engine that will never let you down or run unreliably. The OS line of engines is the way to go. The new AX line of 2 strokes is an improvement over the FX line. OS are always on top of their game and supply great proven products.
I have seen GMS engines that ran perfect one day and the next day would run so unreliably that you risked losing your plane. Buy the OS!!!

Last edited by Trumpet; 10-20-2009 at 09:52 AM.
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