2 Stroke Engine Set-up & Tuning

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A quick guide to setting up that go faster device on your engine! Yes the.... Carburettor. This is a very rough guide! because of different engine sizes and different types of carb's. It will vary but it´s a good starting point. Carburettors are supposed to be factory set, but more than often then not, they arn´t. The only way to find out is to run it.

Rough setting of idle on a carb

2. Main needle (top end) adjustment

Fuel and fire her up! Let the engine warm for about 30 sec´s at full throttle, now you are going to set the main needle valve by setting the engine at full throttle. The sound you are wanting to hear is a clear, crisp and constant sound. If the engine is "4 stroking", then it is running too rich, lean it out by screwing the main needle in (clockwise) until the engine rpm peeks, then richen it by 2 clicks, hold the nose of the aircraft up, (still on full throttle) if the engine starts to die, then you need to richen it by unscrewing (anticlockwise) by 1 to 2 clicks and check it again with the nose up. You should get to the point where the engine note should not change from the horizontal to vertical position on full throttle. There, you have just tuned the "top end", easy wasn´t it?

4. Handy Tip

If you find the engine is fine with the glow lead attached, but slows dramatically or even stops as soon as you remove it, the glow plug is "cream crakered", time for a new one. The instructions that come with the engine should recommend a suitable plug to use, if not for starters try a good old "bullet proof" Enya No3 for engines up to 0.90.

5. Too Hot!

If the engine has got too hot, allow it to cool down as this will affect the tuning of the engine!! You will know when you´re about there, because a well set up model engine will have the throttle response very similar to a racing car!! Instant pickup from "longish" periods of idle and a smooth return back to idle. GOOD LUCK. It sound´s a pain to do, but it's actually fairly easy, and makes flying a lot more fun with a powerful and reliable engine.

1. Engine Set-up
Where to start, before you start!

Assuming you have a computer radio, adjust the carburettor throw using the "T.ADJ" setting so that the carburettor barrel is fully opened in the carburettor housing when the throttle stick on the transmitter is pushed fully forward in the full throttle position.
Pull the stick fully back to the idle position. Open the main needle approx. 2 turns, place a modelling pin into the body of the carb and adjust the throttle barrel again by using the "T.ADJ" setting in your transmitter until it just makes contact with the pin, this will establish a rough barrel set-up gap for idle running.
Fine adjustment can be made up at the flying field with the engine running and tuned. Remove the pin and store the settings in your transmitter. Now fit a length (6-8 ") of fuel tube to fuel intake nipple on the carburettor gently blow down the tube, if you can just about hear air escaping, it´s set about right. If it is easy to blow air through, then the slow running needle needs to be screwed in (clockwise), if you go blue and nearly pass out trying to blow, unscrew the slow running needle (anticlockwise) until you can just hear air escaping. Use only 1/8 turns at a time for this adjustment!

3. Slow running (bottom end) adjustment

Firstly I suggest that you make all slow running (bottom end) adjustments with the engine stopped, as the adjustment screw is generally situated very close to the turning "razor like" propeller. Stop the engine, make the adjustment, restart the engine, perform tests, stop the engine, make any necessary adjustment etc. etc. etc. From full throttle chop the engine back to idle, if the engine very slowly drops back to idle and it cough´s, splutter´s and takes it´s time to reach full rpm from being at tick over for 20 seconds then the bottom end or slow running needle is set too rich. Screw it in (clockwise) by no more than a 1/8 of a turn at a time and repeat the test. If however the engine just dies when you open the throttle from being at tick over for 20 seconds then the bottom end or slow running adjustment is set too lean, unscrew it (anticlockwise) by no more than a 1/8 of a turn at a time, and repeat the test. As you do these slow running adjustments make sure you continue to check the main needle setting (readjust if necessary) on full throttle as described in "2. Main needle - top end adjustment" as this will alter slightly during the set up procedure of the bottom end.

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