My EM2/M19:
Straight from the package:
- no spark
- no compression
So ... no start
The stripped end of the high tension lead had slipped down the sparkplug boot and didn't make contact with the plug, an easy fix.
I thought the intake valve might be sticking and a drop of light oil to the valve stem would fix that, but no. I ended up pulling the cylinder head and removing the intake valve. There were some tiny specs of debris on the valve seat. After cleaning and lightly lapping the valve to its seat the compression had greatly improved.
I believe both issues have developed during transport. The corners of the box clearly showed it had been subjected to some rough handling. Despite the excellent packaging the little engine was probably subjected to jolts and shocks.
After my fixes, the engine ran, but too fast to my taste, and it stopped abruptly after half a minute or so ... again no spark! Everything seems in order with the plug and its lead. So, what now?
Then I remembered some YT videos by @RonaldWalters, where he uses just two AA batteries and a dummy. Apparently the ignition module can malfunction when fed 4.5V, and using just 2 batteries can prevent that. So, I printed Rons STL for a dummy and fitted it with a 50mm brass screw. Using this, the ignition was much more stable and the spark seemed stronger as well (thank you @RonaldWalters for the tip and for sharing the STL for the dummy on Thingiverse).
It still was not an easy starter, it needed a good spin with the cordless drill, and once it was running, it still ran too fast and irregularly.
The governor fly-balls were hitting the cylinder cooling fins, the valve rocker had a lot of lateral play and the tappet clearance of 0.5mm seemed too much.
The lever that is operated by the governor to hold the rocker up (and the exhaust valve open) couldn't engage well, the rocker danced from left to right like a Dutch football fan causing the lever to often miss its mark. I tightened the clevis where the rocker pivots, removing the lateral slack. No more dancing rocker.
I reduced the tappet clearance to 0.25mm
Next I moved the disc that holds the fly-balls up on its shaft, a millimetre or so. Now the governor engages at lower RPM and the balls don't hit the cylinder anymore (thanks @ThomasPCGuruENGINES for the tip).
The engine now runs stably, the hit&miss engages and keeps the RPM much lower, however I feel the engine lacks some power. A timing issue? There's still room for some tweaking.
So, after reading all this, you might think I'm not happy with this little engine, but that would be the wrong conclusion. I'm actually quite enthusiastic about it, I like to tinker and tweak, and the open design of the mechanism allows for a lot of that.
