Stixoz

G'Day all,

I'm planning on running in my OS 46 AX today and have done a fair bit of reading on running in and tuning these engines. The 1 thing i can't find is where exactly do you adjust the low speed needle valve if i need to?

My best guess is that is the tiny flat head screw that is set inside the bolt that holds the throttle arm on, is that right?

I don't want to go playing with anything that i'm not sure how it works and the manual doesn't really show you, it just says how to tune with it not which screw it is.

Feeling a bit stupid here but any assistance would be greatly appreciated

Stix

flaminheli

Yes you are right on the location. You should not have to adjust it much if at all.
This might help you make the determination if it needs to be adjusted.
[link]http://www.gettingairborne.com/engines.html[/link]

RCKen

My Feedback: (9)

This is absolutely correct. However, don't make any adjustments to the low speed needle until you absolutely are sure you have to. I have 6 of these engines and I can't remember making a low speed needle adjustment on any of them. In most cases you will find that they will run fine right out of the box needing no adjustments. Too many people starting out in the hobby will start twisting the low speed adjustment when it's something else that's actually the problem.

Ken

Stixoz

Cheers guys!

I have the opinion that if it ain't broke don't fix so i don't plan to be tinkering with it. I just hear it referred to in and reviews and in the manual for tuning this engine so thought i would look like a goose and atleast find out which screw it is so i don't loosen a carby mounting mount bolt or something lol.

Cheers guys!

Stix

Jetdesign

My Feedback: (8)

Yep, use a tiny screwdriver - the screw is in the center of the throttle arm.

There might be a few different thoughts on this, but my feeling is to get at least a couple of tanks of fuel through the engine before messing with the low end needle. The low end 'mixture valve' comes 'set' at the factory; it's usually set rich, but is at least set to where you should be able to get the engine running and idling reliably and have just a bit of hesitation with acceleration. The low end (in my opinion) should really just be a fine tuning of the acceleration.

Having the engine running on the rich side won't damage things, but running it too lean will.

And don't feel stupid - there is a lot to this hobby, especially when doing it on your own. It wasn't that long ago when it all seemed totally foreign to me. I started up my 46AX, thought it was insanely loud and powerful, and now it feels and sounds like a toy to me Ask away!

safeTwire

My Feedback: (2)

I agree big time about running a couple of tanks through first, of course allowing a good cool down period between each tank full. After, set the high speed needle a click or two to the rich side of full lean (after all, its new). Hold the nose up and the engine should scream. If it boggs down, its too lean. Next, you are ready to make certain about engine performance as you move the throttle ( smoothly and at a good pace, not too fast) from low, through the mid-range, to full open.

This is where the low speed needle comes into play.

At this point, the low speed needle is ripe for adjustment.. The goal is to have smooth rpm transmission from low to high throttle BEFORE you take off.

New OS engines usually need leaning of the LS needle. You have to try, maybe a 1/16 or 1/8th (or experiment and go drastic like 1/4 turn and see what happens) of a turn at a time, then fire up the engine and test. Repeat as necessary until its right.[sm=wink_smile.gif]

When atmospheric conditions change, mainly severly like from summer to freezing cold, you most probably will have to re-adjust both needles.

Its no big deal, and the sooner you get the feel, the better IMO. Good luck!

w8ye

My Feedback: (16)

If you get the low speed needle in too far, it will destroy your throttle acceleration and/or the effectiveness of the high speed mixture needle

safeTwire

My Feedback: (2)

W8Ye's correct, and this too is part of the learning process!

If this happens, back the LS needle out until it's flush with the carbureator body's surface. This yields a "ballpark" LS needle setting that will allow the engine once again to start and run.

Point I am trying to make here is that I think its better to screw up adjustments so bad that the engine wont run at all...THAN... have a flameout on takeoff. (Those really stink no matter how good of a pilot you are)

Experiment with (slight) adjustments, test then re adjust. Its half the fun IMO, and , your airplane and wallet with be very thankful!

Jetdesign

My Feedback: (8)

I understand the point of making drastic changes to observe the reactions, however the low speed needle is sensitive to 1/32 of a turn, and turning in and out isn't the best for the rings.

Leave the low speed alone for now; run a tank through as per the manual (two and four stroke bla bla bla), then adjust the high speed lean enough that you feel the engine is reliable - won't quit on acceleration, and fly fly fly.

OS engines break in flying - one tank on the ground, adjust to reliable transition, and fly away! After a couple of days, see how you like the transition. Mine needed ONE slight turn to the right for PERFECT transition (which I did after a few weeks of flying actually) and I haven't needed to touch it since. Now has 14ish gallons of fuel through it.

safeTwire

My Feedback: (2)

Turn the "bleeping" LS needle in or out a little at a time as needed until the engine transitions smoothly from low to high throttle. Adjust main needle once again. Not a good idea to takeoff until the engines right. Case Closed!

Pristine piston rings aren't going to do you much good, when your plane is smashed to smithereens!

jetmech05

please don't try to tune this engine...break it in first

safeTwire

My Feedback: (2)

sorry about my last post stixoz, it was rough and unhelpful for you.

Yes, break the engine in first. I assumed you were going to do this.

bruce88123

jetmech is right, nearly senseless to tune the low speed before break-in is complete as it will throw you off.