patrick_ashour

HI Freinds,
Last weekend I break in my new GMS 47 and test fly my Sky Raider Mach I.
I have dificulties with adjusting my engine !
Any experience with this engine ?

Thanks,
Patrick

Spicoli

I have 2 of them and they both leak air through the front bearing.I wont ever buy one again.Some people seem to like them.

ooooo

These engines are better than the OS equivalent. Newbies should keep away from them though as they don't know enough about engines to properly tune and take care of them.
Ask an instructor or an engine guru at your club for help. This seems to be a tuning problem rather than an air leak problem.
That WM Sky Raider Mach I is one awesome trainer. The engine for that plane really is the ASP/Magnum .52 4 stroke. That's the best combo I've seen so far. Flies better than the Avistar.
You didn't give too much info about the probs with the engine...so I can't help as to why the engine is not dialled in, but..once again, ask someone at your club.

Cheers.

DarZeelon

Patrick,


How did you break the engine in?

If you did not do it as described in [link=http://www.rcuniverse.com/forum/Tapered%2DBore_Engine_Break%2Din_%2D_Upgraded/m_1850473/tm.htm]this thread[/link], it could be incomplete, or damaging.

Repeat the break-in, properly this time.


If you did it properly, just ask a more experienced modeler for help.
The idle mixture is probably incorrectly set.

It almost invariably comes unadjusted from the factory, in most engines.

Spicoli

Kaz,
I am not a newbie.I run 2 gms47's,2 OS46fx,OS 50,Webra 50 .I abuse them all on Spad3d's and combat planes and quickie 500's.
How many GMS's do you use?How many 46fx's do you have too compare them too?
The problems I have encountered -are air leaks
The worst air leak was through the bearings.It rendered the needle valve useless.I fixed it by removing the bearings and putting RTV in the channel going from the bearing towards the carb.It worked for a couple months before the old symptoms started coming back.
One of my GMS's had to have a second hand carb just to get it started.
The quality control on them is terrible.
The GMS will sag in a high G turn the OS won't
A friend of mine had a crank so out of wack from the factory that it broke 6 mufflers from the vibration before he figured it out.
The front bearings on one of mine could be takin out by just shaking the case.How many quality engines have bearings that loose ?
What kind of company would sell an engine and tell people it is not meant to be shut off.
Kaz ,It sounds to me like your the newbie.The factory knows they leak air that is why they don't warranty them if they don't shut off with the throttle.
I would be interested in hearing your experience with GMS and OS forty size engines
I have discussed the GMS thouroghly with everyone in my Club and they all think same.We all tried them and we all went back to what we were using before.
If anyone out there is willing to trade their OS for a GMS let me know.

DarZeelon

Kelly,


The bearings in a shaft-valve two-stroke engine are not supposed to offer a gas-tight seal.

The rear bearing is almost invariably unsealed and unshielded, in most such engines.
The front bearing in most engines is shielded; your OS.46FX and .50, for example.

But do take a look at your Webra .50, if it does still have the original front bearing.
Its front bearing has no shield, or seals. It is fully open, in fact.

There are several other engine makes, MVVS among them, that also use some open bearings.

The seal problem that you had in your GMS resulted from excessive clearance between the crankshaft and the crankcase, in the crankshaft valve area, just under the carburettor.

The fact that you temporarily rectified it by effectively sealing the front of the engine, just goes to prove this.

And yes, the GMS parts fit was terrible, but it may have already been fixed.
In engines from Sanye China (Magnum, ASP and the like), it has been improved quite significantly.

Spicoli

Dar,
I realize it is not supposed to be a gas tight seal.My point was that it was such a crappy fit you could take the drive hub off shake the engine in your hand and the front bearing will fall out and hit the floor.
But I know I got a quality engine it doesn't have one of those cheap nickel liners

Flyboy Dave

My Feedback: (21)

The new GMS .47's are top notch in every way. We have run up 4 or 5
of them recently, and everyone ran perfectly right out of the box. The
low end screws didn't need to be ajusted....

....and they just flat scream. For $65.00 they can't be beat.

FBD.