What each needle does?! Frusterated  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> What each needle does?! Frusterated
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What each needle does?! Frusterated - 12/12/2006 11:09:53 PM   
Zephirus79


 

Posts: 57
Joined: 11/9/2006
From: , GA, USA
Status: offline 		Trying to tune my engine... and its all out of wack and I dont know what I need to adjust...


The engine starts, and dies when I throttle up. Richening the low end fixed that but still it STILL either dies or transitions HORRIBLY. Once it is high it doesn't run as fast as it should. When I lean it just 4 clicks the engine reves up and sounds normal. But then when I pinch the fuel line to the carb, engine dies indicating its too lean. But it barely runs if I just richen it 4 clicks. Engine also dies coming from full throttle to idle....


I dont know which needle controls what. Does the low end control from idle to mid throttle and then the high needle takes over from there?

Im trying to isolate this problem and Im about a minute away from smashing it with a sledge and pissing on the pieces...


Its a tower .46. I dont know whats going on with it. Before you say air leak, I have pretty much disassembled the engine to check for that. There is no way its leaking now...

       Post #: 1

RE: What each needle does?! Frusterated - 12/12/2006 11:53:38 PM   
Cambo



Posts: 1516
Joined: 6/20/2005
From: Phoenix, AZ, USA
Status: offline 		Is it possible that when you were richening the low end you over richened it.

(in reply to Zephirus79)
       Post #: 2

RE: What each needle does?! Frusterated - 12/13/2006 1:08:49 AM   
microsprint9



Posts: 417
Joined: 11/20/2004
From: london, ON, CANADA
Status: offline 		I know this is for an OS engine, but i'm guessing you don't have your manual for that engine if you don't know what the needles do, read thru this manual http://manuals.hobbico.com/osm/46ax-manual.pdf and then try to find out the original low speed needle setting and adjust. Most engines come from the factory with the low speed set fairly close to the optimum setting which your not supposed to adjust til after break in. Remember the tank postion is also critical to proper engine performance. Make sure you also have the right prop on the engine as well.

(in reply to Cambo)
       Post #: 3

RE: What each needle does?! Frusterated - 12/13/2006 1:15:50 AM   
Campgems


 

Posts: 1928
Joined: 2/18/2006
From: Arroyo Grande, CA, USA
Status: offline 		The high speed valve sets your overall mixture. The low speed is actually a variable mix valve. As the throtle body rotates, it also moves laterly, pulling or pushing the low speed valve into the spray bar, giving a variable mixture related to speed. Grab a tach and adjust the highspeed for maximum RPM, the richen it so you drop about 400 RPM. Now run the motor as slow as you possibly can and keep it running. Adjust the low speed for maximum RPM at this setting. Go back and repeat the high speed adjustment. Repeate the idle mix adjustment. Now, on transision, if the motor just dies or just barly keeps running when you jam the throtle full from idle, the idle mix is to lean, richen it up 1/16 turn. All adjustment should be this fine a movement. Try it again and see how it make the jump to full RPM. Still dies or is still stumbling, richen it again. This time re-do the high speed. With each adjustment of the low speed, you need to adjust the high speed as you are changing the overall mix. If it seem to be getting worse when richening the idle, pinch the fuel line off with the engine running at it's slowes speed. If the engine just dies, you are still to lean on the idle. If it reves up and then dies, you are to rich. Adjust accordingly. Remember 1/16 turn at a time. It's a slow process, but one that will be much more productive than hunting for the right mix. After going through this and you are still having problems, smear some vassline around both needle valves and also around the carb to manifold or crank case joint. Repeat the adjustments and see if all is well now. This will tell you if you have an air leak. New O'rings should fix the leak if you do.

Don


(in reply to Zephirus79)
       Post #: 4

RE: What each needle does?! Frusterated - 12/13/2006 1:37:19 AM   
Cyclic Hardover



Posts: 7221
Joined: 5/7/2002
From: New Mexico, USA
Status: offline 		I've been at this 10 years and i don't even know what you'll are talking about. The manuals are full of good info if you look in the right place and the manual is also full of ____! Keep it simple. Tuning any size 2 stroke is too easy or can be a royal pain.

The low end needle is the root of all evil. Master this and you'll never have a bad running engine. I don't and haven't for years. get it right the first time and you rarely need to adjust it again in any given season.

Sounds like everything is out of whack so lets keep it simple and start over. Open the high end needle about 3 turns, close the low end needle completely. Remove the fuel line from the carb nipple. Attach another fuel line for you to blow into the carb with. Make sure the surrounding area is quiet. Now at the same time, blow into the tube and open the low end needle until you hear a hissing noise, then stop. After this, put the regular fule line back on the carb. Your low end is now set "in the ballpark area" "Note-factory settting are useless."

Okay your high end is already open about around 3 turns. Start the plane and rev it up abit. Now it may sound sloppy and all but stry and keep it going and open it up full speed if you can. Once done, close (lean) the high end until the rpms transistion from blubering rich to a nice high speed sound. Then rev the engine a few times to keep the fuel from loading up.

Next thing is to let the engine idle and or set the idle rpms. with thw engine at an idle, either reomve the line fromthe carb nipple or pinch the line with pliers and wait for the engine to stop running. -----LISTEN TO THE RPMS AS THIS HAPPEN! If the rpms increase as the engine quits, your low end is still to rich therefore leanit just a tad (1/16 inch). If the rpms just go down and quit, low end to lean, therefore open the low end a tad.

Now each time you make and adjustment to the low, retune the high, this brings it all together.

By removing or pinching the fuel line off tells you if any adjustments you just made had any effect on the engine at all! Is usuallset mine for a very slight increase in rpms on that test. With this, your engines should run perfectly.

_____________________________

Retired Army Aviator - Excuse Me! You sold me a hair with a cake around it!

(in reply to Campgems)
       Post #: 5

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