Hi Jameson
I have a VM-60 that I bought in November and had similar difficulties with. Here are some observations from my experience:
-The engine needs to heat cycle to break in. I tried to do the run-in in cold weather and this didnt work because the engine running rich only got to 80-90 degrees. It needs to get hot (ca 130 degrees) and cool off again. Then the parts wear together.
-Aspen fuel is not good until the engine has a lot of hours on it. It will start great when cold, but not warm at all. I tried to run-in my engine with Aspen and this was frustrating because after the first start it needed to sit for an hour to cool again before restarting. I switched to Shell V-Power 100 and that made the run-in much easier.
-The location of the carburettor means it gets warm. When the carb reaches 55 degrees (easily done as its behind the cylinder and above the exhaust manifold) the normal petrol begins to bubble and the engine goes lean. This makes for difficult or impossible warm starts. Get a can of Kältespray. Aspen fuel seems to bubble and go lean at only 45 degrees, so beware.
-The carb settings can be very sensitive and changing props means retuning. Changing fuel means retuning as well. I would reccommend choosing a prop, a fuel, and getting 6-8 hours of run time on the motor, temperatures varying, and load varying.
-After about 8 hours of runtime I have switched to Aspen 4T + Valvoline and the engine runs well.
-Final note: The engine is flyable after 2 hours of running, but it will be 8+ hours of flying before it makes full power. Your first few flights will need minor carb adjustments each time as the engine wears in.
Good luck and let us know how you get on!
Cheers,
Dave
