I'm sure we can all agree that setting your engine's mixture correctly is very important. Remember, compression settings on a diesel are its timing settings. So first let's assume you have no directions and you have never set a model engine's fuel mixture before.
First close the needle making sure not to force it close once it stops. Next, open it one turn and blow through the line, keep blowing while opening until you hear a clear flow of air then stop. It is always better to start from a point of too open than too closed. Too open is too rich and too closed is too lean, a bad place to be. Reattach the fuel line to the fuel tank.
2. Turn the engine over while turning the compression out so as to reduce it.
3. Engage electric starter for a few seconds, turn in compression 1/8th of a turn at a time until engine starts. We never recommend hand starting, either use a spring starter for 1/2A engines or an electric starter for anything larger.
4. Allow the engine at least a full minute to warm up before making any further adjustments.
5. Slowly turn in the needle valve allowing the engine to speed up.
If you go in too far, the engine will do one of two things, slow down or miss. If it slows down then back out the compression slightly and repeat until you reach a point that when you turn it in too far the engine misses at which point you back out the needle until the miss goes away. This is called a safety miss.
Note: All engines after break-in have a sweet spot. This is where the compression and needle settings stay in a specific spot for extended periods of time. If you should use bigger props, creating bigger loads, you will have to reduce your compression accordingly.
6. The optimum setting for power is a balance between the compression and the mixture settings.
7. This procedure is valid for all non-R/C diesel engines.
I'll be posting the procedure for R/C diesels in a future post.
If you ever have any questions, I'm always at the other end of a phone.