valves on a 2 stroke engine? as far as removing the carbon, just check the spark arrestor once in a while on the muffler for carbon buildup. you will notice a severe decrease in power if this happens. dont think you will have to worry about that happening. good luck

It is actually a 4 stroke engine that requires mixed fuel. The hybrid technology reduces emissions without adding weight and the torque is phenomenal. Check and adjust the valves per recommendations, clean the spark arrestor if performance falls off and run Sea Foam or something similar through it to 'decoke'.

I have BR 550. I've used nothing but regular stihl oil so far and no problems. I probably have about 45 hours on mine with no problems. I do plan to switch over to the synthetic oil once I use up my reg oil. I figure I use mine about 15 hours a year. I have no exact way of knowing the exact time as I'll use it here and there for a couple of minutes to going through a couple of tanks a gas per weekend during the fall. I'll service mine once I've owned it for 10 years regardless of whether I'm at 150 or over. Other than that, I'm not going to worry about it. If it ain't broke..

what ratio of fuel do you use?