I'm currently using a Stihl KM90R power head with the attachments, a straight shaft string trimmer and an edger. I've had for 4 years now and I'm quite happy with it. It has enough torque to run an edger, plenty of power to run a string trimmer, even the thicker lines. The engine runs as a 4 stroke but it runs 2 cycle oil gas mixture. The engine is very strong and sounds really nice.
Overall, I'm happy with it. Two things I don't like about it. Low RPM throttle modulation is twitchy. It's is like on/off switch. Idle to mid throttle is hard to modulate. It likes to run mid to high throttle. I had a Honda string trimmer with a stroke engine and throttle modulation is smooth and linear. On the Stihl, It takes 5-10 pulls with partial choke to get a cold engine started. Once warmed up, restarting is easy, one pull without choke.
I also have an Echo with 28cc engine. It is an edger, bed redefiner though. Engine is easy to start, smooth throttle modulation, I think the heavy mass of the edger really smooths out any engine twitchiness. Engine sound is ok. The handle has soft overmold rubber which absorbs the vibration so it is more comfortable to hold. The engine is also powerful.
I still enjoy using the Stihl despite the twitchy throttle and hard cold starts.
This message was modified Oct 17, 2012 by aa335