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Author Topic: LA .25  (Read 2031 times)

Offline Bob Riegl

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LA .25
« on: September 07, 2007, 11:07:30 AM »
 ;) I am trying to settle my mind while contemplating the purchase of the OS.25LA. I have heard some, uncomplimentary comments regarding this engine. They all seemed to end up with scrapping the plastic back plate and needle valve and opting for a venturi mounted needle valve and I guess substituting a metal backplate. These were apprently in an effort just to get the engine to run properly. It seems to me that OS would be aware of this apparent "problem" and have done something about it. What info can the users out there provide for us on the "outside."  HB~>
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Offline dave siegler

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Re: LA .25
« Reply #1 on: September 08, 2007, 07:26:08 AM »
;) I am trying to settle my mind while contemplating the purchase of the OS.25LA. I have heard some, uncomplimentary comments regarding this engine. They all seemed to end up with scrapping the plastic back plate and needle valve and opting for a venturi mounted needle valve and I guess substituting a metal backplate. These were apprently in an effort just to get the engine to run properly. It seems to me that OS would be aware of this apparent "problem" and have done something about it. What info can the users out there provide for us on the "outside."  HB~>

The Plastic back plate will work, however if you over torque the screws or crash you may start a leak.  The leak can be hard to find and drive you nuts.  If I had driven 500 miles to contest, and I got a leak, I'd be mad.  So a preventitive swap out might be a good idea in that case.  But on average, the plastic back plate will work just fine.  If they don't leak they will be fine.  If it starts leaking buy a metal one or send the motor back.

Is it a problem?  OS is willing to put a 2 year warranty on their motor.  If warranty claims were excessive due to a leaky back plate, there would be design changes.  Warranty claims will kill a company, because they are costly to process.  Any claim (aproved or deneyed) the comany looses money. So OS feels good about the nylon back plate.   

On the remote needle valve, most guys would rather run a normal needle, BUT the remote needles do work. 

It depends on your definition of a good run.  Stunt guys are very picky.  The remote NVA has several extra places where a leak can occur.  A lot of guys want to eliminate any potential problem (real or not) , so just toss it. 

I have had good luck with remote needles, but I have removed them form the back plate.  Remote NVA's can be moved to be more protected in a crash.

This is in the combat section and NVA's are the norm here, but most swap the stock one for one off a OS .10 (finer thread) when used on pressure. 

In most applications the stock OS will work just fine out of the box.  If you are a high end stunt competior, you may want to make changes, but most sport fliers will never have a problem.

If the back plate and NVA scare you purchase a Brodak .25.  While more expensive the NVA and back plate are more conventional.



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Offline phil c

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Re: LA .25
« Reply #2 on: September 11, 2007, 07:39:22 PM »
Problems with the plastic backplate on the LA engines are greatly over-rated.  As Bob says, if you torque the screws to hard you can sometimes open up a small leak which will make the motor hard to start.  I've got two with the original plastic backplates that have been disassembled many times with no problems.

Assuming this is for speed limit combat, cut off the stock remote and throw it away.  It is too coarse to use on a bladder.  Get either the standard OS CL needle valve and put it through the venturi, or get the 1a needle valve for the FP 10 engine(Tower part # LXCR44).  Both have a finer thread and work OK with pressure.

Make sure the main bearing is very free.  A tight main bearing will take many many many flights to break in and cause you all sorts of problems with getting the engine to hold a setting.  With the motor disassembled and just the crank in with a prop on it, lube it with fuel and flip the prop.  It should spin at least 10-20 revolutions and come to rest with the counterweight hanging down.  If not, hone it with some 1000 grit sandpaper wrapped around a dowel.  With thousand grit it will take next to forever to take off enough material to actually hurt things.  Plain bearing engines run just fine with lots of slop in the main bearing.
phil Cartier

Offline Bob Riegl

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GMS .25
« Reply #3 on: September 13, 2007, 11:39:14 AM »
Well I bought the GMS .25 from Tower and this engine comes with a throttle---now I have never dealt with a throttle and decided to lock it in open and run on the needle valve. Well I get pops and screaming runs for 5 seconds and it dies---I am running on 10%/20% I am beginning to think that this engine might need 20% nitro---I never fooled with nitro before recently and need some advice. It was labeled as a great engine for combat. When it runs it's a holy hellion, but I don't get long runs and if I remove the battery from the glow-plug it dies---that's why I think I may need more nitro. Any advice.
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Offline Dennis Adamisin

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Re: LA .25
« Reply #4 on: September 13, 2007, 04:15:28 PM »
Bob
The GMS 25 is a sport engine, your 10/20 fuel should be fine, your problems sounds like either mixture way too lean, or air leak.

GMS engines ARE notorius for leaky carb gaskets.  You have to really press the carb down into the bore then lock down the clamping nut to hold it tight.  Put a dime on the top of the carb when you do this, it will make it easier to press it hard.

DId you get the remote needle version?  If so make sure the fuel line connecting the needle assembly to the carb is tight on both ends.  Actually even before you do that you can double check that the vaious fuel line fittings are snug and not leaking.

After satisfying yourself that there are no leaks, attach a piece of fuel line to the fitting and blow through it.  if nothing is passing then start opening up the needle until you hear or feel the air blowing through.  This is a way to ceck that there are no internal blocakges...

Good luck and check back in!
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Iskandar Taib

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Re: LA .25
« Reply #5 on: September 13, 2007, 09:20:45 PM »
If you're going to use it in Combat, take off the carb and sell it on e-Bay. Get a 6-32 DuBro fuel nipple, and figure out how to mount it on the intake stack. On my Magnums and ASPs, I stuff tissue paper down the intake, then drill and tap a hole fairly low down on the intake boss. Get a OS remote needle like Phil said, mount it on some sort of bracket on the plane where it won't get knocked off in a collision (a nylon control horn works). Use a bladder, of course. You can run a venturi, or run it open-face - seems to work either way, open face might use more fuel, and an adjustable intake will allow you to adjust the speed for Speed Limit.

Now.. can you weigh that GMS sans carb and muffler and tell us what it weighs? Just curious, want to compare it to other engines.



Offline Bob Riegl

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Re: LA .25
« Reply #6 on: September 14, 2007, 05:36:59 PM »
OK I did not get a remote carb with this and I don't like the needle valve so close to the prop---I already skinned a knuckle. I am now trying the throttle and closing it to about 1/4 open and I have played with the idle needle and gotten 20 second runs with absolutely no speed. Tomorrow I am going to try the throttle adjustment for starting purposes---the needle valve is a bitch to turn, hence the battered knuckle. I will pick up a remote OS needle valve and install that eventually, and I will say that there is a bit of fuel being spattered about---but I attribute that to the fact the engine is not running at speed---except for those startling quick 10 seconds starts with popping and puffing. I have checked with the needle valve assembly and of course with the needle only open 2 turns I could pop an ear trying to blow air. I will remove the carb and I don't use a useless muffler and weigh it for you for your requested information. I may have stated that this might make a good carrier engine with the throttle assembly, and I will remount the carb using your approach with a dime---though it does have two "0" rings and I will re-check the lock-up. Soonalatah it'll woik. HB~>
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Offline Dennis Adamisin

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Re: LA .25
« Reply #7 on: September 14, 2007, 06:37:57 PM »
Hmmm, sounds like you will be working on this one for awhile!

Try the Tower Hobbies site, look up the parts list for the remote needle version of the engine.  I think you will even be able to take the needle off the carb and build it into the remote system.

BTW I would start with the needle 3 to 3.5 turns open.  That should be TOO RICH but will let you get it started and running steady so you can dial the needle to a good setting.

HOWEVER, what Mr Taib said about getting rid of the carb and using a CL venturi makes a ton of sense!

Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Iskandar Taib

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Re: LA .25
« Reply #8 on: September 16, 2007, 08:31:58 PM »
The remote needle set up above works with bladder tanks, not with suction. For suction, you need a smaller intake. If you want to do that, just use the existing venturi.

If you decide to try the bladder, the OS needle is the one to use. Most other RC needle valve assemblies (other than the "remote" ones) don't have an integral inlet nipple (it's on the carb body instead), and would therefore be useless. The OS .25LA backplate-mounted remote does work (I've seen Chris Gay use it with a bladder) but will get knocked off in short order because it sticks up.

When used with a bladder, the needle is only opened up a half turn or so. You point the nose down and adjust the fuel dripping from the venturi - for a .25, it's about a half inch unbroken stream. This will get you close. For information on the use of a bladder, see:

http://www.clcombat.info/bladder.html



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