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Author Topic: OS LA .46, .40 OEM needle valve assembly?  (Read 2742 times)

Offline Avaiojet

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OS LA .46, .40 OEM needle valve assembly?
« on: December 08, 2012, 01:49:18 PM »
Is anyone using the factory needle valve assemble, the one that has the needle assembly attached to the rear cover?

Or do you just toss that and get a NVA that fits in the venturi?

Charles
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Offline Geoff Goodworth

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #1 on: December 08, 2012, 03:48:43 PM »
The first thing I did with my LA 46s was toss the plastic backplates and the rear needle setup. I bought a couple of backplates from Tower when they were running out the FP 35/40 parts stock.

Some people have reported success with the rear needle, I'm not one of them. I also replaced the screws with cap head screws

I use the factory needle valve through the venturi. Some people will argue that the ratchet control on the factory NVA does not provide sufficiently fine adjustment but I'm not flying at a standard to notice. The factory NVA is 3.5mm OD and the standard ST NVA is 4mm so the crankcase and venturi need to be drilled out to accept the infinitely adjustable ST NVA. We have the best of both worlds in Oz as we have a modeller making ST-style NVAs with 3.5mm OD. #^

Offline kenneth cook

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #2 on: December 08, 2012, 08:09:55 PM »
              I've been using my factory backplate for 7 years now without problems. However, I did what most recommended early on. I used washers under the screws I believe #4 and I also used Anaerobic gasket sealer made by Permatex. This stuff comes in small tubes and isn't a RTV gasket maker. I found several problems using the rear remote mounted needle. For one, I feel the needles don't have a long and fine enough taper to dial the engine in to where we like to run them. It seems right about the time your getting the engine into the sweet zone, it falls off due to it entirely cutting off the fuel supply. Starting becomes most problematic as each time I would have to start the engine, I would have to open the needle to allow adequate fuel draw initially even though it ran a few minutes prior. Also, the fuel supply wants to constantly siphon back to the needle. All problems and reliability was cured with the up front needle valve assembly. One thing I don't like about the up front needle is the way the spring attaches to the needle. It screws on. This sometimes has a tendency to loosen when trying to richen the needle. The little aluminum knob likes to turn and the needle doesn't. I epoxy the knob and solder the spring onto the needle assembly. Other than that I do prefer the up front set up. Ken
« Last Edit: December 09, 2012, 06:56:26 AM by kenneth cook »

Offline FLOYD CARTER

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #3 on: December 09, 2012, 10:13:00 AM »
I have reported my opinion before, but here it is again.  I find the rear-mounted needle valve on the OS engines to be an important safety feature.  I haven't noticed any engine-running issue with the stock NVA, and some local people are also running stock NVA with success.

Floyd
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Offline kenneth cook

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #4 on: December 09, 2012, 10:29:37 AM »
                 I wish that OS and I've requested them to do this was to supply us with the same thread as the OS #1A needles. These would make a great remote needle valve assembly for us that fly speed limit. I do use the spraybar assembly from the remote needle valve assemblies but I use needle valve assembly from above. In regards to the statement Floyd made, I wish I had of known this as I disposed of all mine. I had no use for them as they're just too problematic for my liking. They really only work on profiles .  In our club, the only users of this assembly was those who used it initially typically growing tired of the problems I explained above. Had I known that somewhere someone was using these, I would've gladly given the parts to those who desired. At the time, I couldn't give them away. I've written to OS as they have a consumer contact e-mail requesting your likes and dislikes. They also have a section that invites designs that you would possibly like to see. I've submitted my requests on several occasions in regards to the remote assembly just requiring a finer thread as this is what's required for running an engine on bladder. I received no responses even one stating thank you for your response. I feel the needle is well designed, it's just that it never seems to fully lean the engine out like the up front assembly does. I certainly do feel the response is quicker on the up front assembly as well. As for safety, one can't express that enough. I suppose the best thing is to where a glove and keep your fingers out of the prop. Seeing that thousands of engines have a up front needle valve assembly, it's just something we've all gotten used to. Don't reach over the prop and be careful. I feel that removing the battery clip from the plug is more dangerous than adjusting the needle. I've seen more people injured removing the clip or nicad ignitor  than any other procedure in this hobby.  Myself and my son have both been bitten doing this requiring stitches. Keep your hands away and don't get to complacent with your start up procedures. Ken

Offline Cliff Henke

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #5 on: December 09, 2012, 10:14:36 PM »
Is anyone using the factory needle valve assemble, the one that has the needle assembly attached to the rear cover?

Or do you just toss that and get a NVA that fits in the venturi?

Charles

Charles, I guess I'm just lucky. The last motor I purchased ( July 2012 ) ( OS46LA ) for a profile bi-plane ( 38 Special ) has been the easiest motor to crank and tune with incredible power between 8400-10200 rpm's that I have ever owned, including the family vehicles. As far as the rear located NVA, no problems in the least. A lot easier that through the venturi. I like it.

But I'm no pro by no means but I do know if I like something or really like something. That's why I'm purchasing another one for the Twister. Just sharing my opinion on this motor.
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Offline Cliff Henke

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #6 on: December 17, 2012, 09:05:37 AM »
I was just wondering after reading some post made concerning this engine.
Am I robbing myself of something by staying with the rear located NVA on this deal ? It hasn't given me a problem yet.... I fly circles about once a week............

If it is giving me a problem, what are the symptoms ?  Still trying to learn............trying.............HELP !

Thanks in advance, Cliff
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Offline Avaiojet

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #7 on: December 17, 2012, 11:39:05 AM »
I was just wondering after reading some post made concerning this engine.
Am I robbing myself of something by staying with the rear located NVA on this deal ? It hasn't given me a problem yet.... I fly circles about once a week............If it is giving me a problem, what are the symptoms ?  Still trying to learn............trying.............HELP !
Thanks in advance, Cliff

Cliff,

Just saw your reply!!

Great news actually. I don't play piano, but do use my fingers for other things. I don't mind keeping them away from the prop if I can.

I may, on your advice and experience, elect to keep that rear mounted NVA.

Thanks for the reply and great information!!

Charles
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Offline Steve Helmick

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #8 on: December 18, 2012, 12:22:14 AM »
I used the stock RNV on the .25LA for awhile, and found that after I choked the fuel into the engine, the line from tank to NV ran back into the tank. When the engine fired up, it seldom stayed running until the line got filled again, IIRC. I think a good part of this is because the NV threads are very loose and don't seal against air leakage. If you really want to use an RNV, the Magnum units seem to be very good...very snug threads and they seal off when fully closed. Maybe Glenn Reach can give a 1st hand report (or retort) on that notion? I put them on a pair of MECOA .28's that ended up in his mittens. How did they run, Glenn?   ??? Steve 
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Offline Joseph Lijoi

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Re: OS LA .46, .40 OEM needle valve assembly?
« Reply #9 on: December 18, 2012, 11:09:22 AM »
             I've been using my factory backplate for 7 years now without problems. However, I did what most recommended early on. I used washers under the screws I believe #4 and I also used Anaerobic gasket sealer made by Permatex. This stuff comes in small tubes and isn't a RTV gasket maker. I found several problems using the rear remote mounted needle. For one, I feel the needles don't have a long and fine enough taper to dial the engine in to where we like to run them. It seems right about the time your getting the engine into the sweet zone, it falls off due to it entirely cutting off the fuel supply. Starting becomes most problematic as each time I would have to start the engine, I would have to open the needle to allow adequate fuel draw initially even though it ran a few minutes prior. Also, the fuel supply wants to constantly siphon back to the needle. All problems and reliability was cured with the up front needle valve assembly. One thing I don't like about the up front needle is the way the spring attaches to the needle. It screws on. This sometimes has a tendency to loosen when trying to richen the needle. The little aluminum knob likes to turn and the needle doesn't. I epoxy the knob and solder the spring onto the needle assembly. Other than that I do prefer the up front set up. Ken

I understand that it isn't unheard of for some engine rework/specialty stunt engine manufacturers use something other than aluminum for the backplate, or make some kind of pad out of teflon screwed to the backplate.  The reason for this is to keep the conrod/crankshaft from creating aluminum chips if it contacts the backplate.  This will foul the plug and cause a flameout.  An engine expert can verify this.

I think if the backplate is treated as a service item, and precautions are taken, that there won't be any problem.  The rear needle, if the engine is broken in and doesn't vibrate excessively, should be ok too.  I have had isuues with rear needles in the past, but I think these were vibration problems.   

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