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Old Apr 07, 2015, 04:43 PM
pinball7890 is offline
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HELP: needle valve rotation

Hi Expert,

i have one small doubt which need to be clear before break-in my OS ABC 46 glow engine. i apologize for creating a new thread for this stupid question(new into this forum also in RC world, not sure about rules and regulation).

1. as per my engine manual , there it says rotate the needle valve to 2-2.5 turn (C-Clockwise) . now my question is what does one turn mean, is it 360' rotation of needle valve equal to one turn or ~30/40 degree rotation by hand/finger is one turn.

2. also in manual document it says "four-cycle" to/form "two cycle" , what does it mean? what is "four cycle" and "two cycle" mean ?

3. if possible could anyone redirect/suggest me any online resource where i could find break-in process for my engine(mine is OS 46 ABC glow engine).

i apologize for my bad english and any kind of expert input from your side is highly appreciated.

Thanks in advance
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Old Apr 07, 2015, 04:51 PM
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Welcome to the forum.

Yes a 360 degree rotation of the needle is one turn.

Four cycling is when a two stroke engine is set very rich, so rich that it tends to hit and miss and acts like it is firing every other stroke. They call that four cycling.

these links might help you too
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Old Apr 08, 2015, 07:30 PM
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Good post Earl.
Pinball, until you fire the engine you won't know where the needle should be set. It changes a little based on altitude, temperature, and humidity, among other things. On any given flying day once you get it right you most likely will not need to change anything but from day to day it may change A LITTLE.
Some guys fiddle with the needle every chance they get near the plane but in reality if you are several clicks to half a turn rich of full lean you will be safe for the day and have a happy engine for a long time.
Having owned several high performance racing engines, half a turn or more rich is not uncommon to prevent a lean run.
Lean mixture is the death of an engine.
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Old Apr 11, 2015, 04:17 PM
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And C-Clockwise means counterclockwise
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Old Apr 11, 2015, 06:51 PM
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Welcome to the forum.

Follow the instructions presented for break in where the engine will seem to be so rich it barely runs. Under NO condition do you want to lean out the high speed needle yet until you have at least a few tankfuls through it. In fact, it will be so rich that will be messy, but happen rather quickly. That's why it is better, (but not necessary) to use a test stand than have that excess slathered on the airframe.

I found on most 2-strokes you will see the Low Speed needle, the one mounted within the rotating barrel centered in the throttle arm, even with the end of the barrel housing itself. That will be a pretty good place to start.

Also, with almost every 2-stroke I run your High Speed needle will end up approx 1 3/4 turn out from bottom for final tune. So for break in backing it out 2-turns should be adequately rich. Any more and the engine may be too rich for full throttle and cut off as you add more.

There should be instructions on that proper break in and here is one showing an OS 46AX where the HS needle is momentarily leaned out, then richened again:

Tiger 3 Phoenix OS 46 AX II break in (1 min 20 sec)

You will notice the engine richen so much it starts to do that 4-stroke mentioned earlier.

Once the engine has a few tanks you can lean it out for longer periods. Note however that adjusting the HS needle will also now affect the LS setting and it may have to be "Tweaked" a few clicks at a time till you have a reliable idle. The term reliable not only means it idles smoothly, but transitions to full without stumbling, (usually a sign too rich) or cutting out, (too lean).

Best make any LS needle adjustments with the engine stopped to reduce the risk of prop strikes.

If you are unfamiliar with nitro engines there are a few other things to concern yourself with very early on. First is that most plastic props have mould flash on their edges that can be extremely sharp. You want to trim or sand those off to a smooth finish.

Second, you want to balance the prop. This minimizes vibration and stress on the engine and airframe.

As a final warning, NEVER work within the prop danger arc while running at anything above idle. That arc is from even with the prop plane forward. This is where the prop can eject at high speed and energy if anything happens.

On a final note, be prepared to replace the glow plug. Break in causes microscopic particles to wear from the moving parts and those can impinge on and damage or compromise the heating coil. Although each symptom is a sign your mixture is off peak, difficulty starting, poor performance or cutting out when external power removed are also good indicators that really become apparent once the break in is complete and mixture set for peak.
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Last edited by Cougar429; Apr 11, 2015 at 07:10 PM.
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Old Apr 13, 2015, 09:28 AM
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For the OP,
Since you are also on the India forum, suggest you seek help from an experienced modeler in your area. That would ensure your learning curve is shorter/ you do not end up with a ruined engine.
While you can do it all by yourself with help of advice here and on local forums, the above two distinct possibilities can not be ruled out.
Again going by your posts, please make sure you have mounted the engine properly(means securely) in a test stand or your model using adequate size screws/bolts & nuts and they are adequately tight, you have a correct size propeller mounted correctly and secure on to your engine and use safe practices and treat the running engine with a fair bit of respect (the same you would be showing to a piece of machinery that could seriously chop things) while you learn about your engine and run it in
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