Basic 2-stroke engine break-in procedures

29/March 2017

(See manufacturers instructions for abc and 4-stroke engine break-in. When no break-in instructions are given, 
run a couple tanks through the engine at a very rich setting, e.g., turn out the needle valve 4-8 turns: 
Run 2 min. at 1/4 throttle, 2 min. at 1/2, 2 min. at 1/4, 2 min. at 1/2, repeat, repeat.)

  1. Turn out the needle valve two turns (from closed).
  2. Prime the engine by squirting several drops of fuel directly into the open carburetor. 
  3. Start the engine slightly above idle throttle. (Keep repeating until the engine stays running. If it won't start, re-prime the engine. If it won't stay running, try starting it with a slightly higher throttle setting and/or "goose" the throttle.) 
  4. Let the engine warm up for a minute.
  5. Slowly advance the power to full throttle (taking approximately 20 seconds).
  6. Richen (turn out) the needle valve to the point were the engine is barely running due to being extremely rich—how ever many turns it takes—and run the tank dry.
  7. Repeat. Two tanks should be enough to break-in the engine. 

Note: As the engine breaks at full throttle it will speed up. To avoid excessive rpm's (heat) during break-in, 
richen the needle valve so that you hear only gradual rpm increases every few minutes from what it sounded 
like a few minutes before. When the rpm's remain the same for several minutes the engine is likely broken in.

Universal engine tuning for flight (2 or 4-stroke):

  1. Return the needle valve to 2 turns out (from closed).
  2. Start engine slightly above idle.
  3. Run smoothly up to full power.
  4. Slowly turn in the main needle valve, 1/8th turns at a time, and wait a few seconds after each turn of the needle valve. Continue to turn in the needle valve, listening to the engine speed up. When the engine plateaus, i.e., no longer speeds up when you turn in the needle valve, or starts to slow down (too lean), turn out the needle valve backto the position where "peak" running was detected by ear, then turn out the needle valve 1/4 turn further to ensure a "slightly rich" setting and therefore reliable in-flight run.

Engine trouble shooting (mid-range through full power) rules-of-thumb:

Consistent, yet unacceptable running engine: Either the glo-plug needs to be replaced (the glo-plug is easiest to check, so check it first) or a needle valve needs adjusting. If problems remain, and you're using a “caster” oil based fuel, try Morgan Fuels synthetic “Cool-Power” and bump up the nitro content to 15%. (Synthetics burn cleaner, and therefore are less prone to fouling the glo-plug or binding the engine and causing poor engine performance.) 

Inconsistent running engine, e.g., the engine runs fine for a few moments and then speeds up or slows down on its own, or runs fine for one minute, and then poorly the next:
 Trouble shoot the fuel system. Look for splits in the fuel line, pinched fuel lines, dirt/particles in the carburetor, tank position, etc..

Note: If the engine does not change whatsoever when adjusting the needle-valve, something is seriously wrong, and if replacing the fuel system and the glow-plug and flushing the carburetor doesn't fix it, it may have to be sent in to the manufacturer.

Low-end idle adjustment (if required) rule-of-thumb:

  1. If engine will not idle slowly, or will idle well only for a few moments and then quits:
    Simply turn the low-end adjustment in or out (which way does not matter), but keep the low-end adjustments very small. 
  2. If idle performance is worse than before, and hopefully it is because that tells you that the other way is the direction to go, slightly adjust the low-end in the other direction.
  3. If idle performance/consistency improves, continue turning the low-end in the direction that improved the idle. Make very small adjustments—waiting a few moments after each adjustment—until the idle worsens, and then reposition the low-end to the previous position of best idle performance.