You have to keep in mind that these engines are very simple devices. Hundreds of thousands of chain saws, weed wackers, blowers and other stuff is sold every year with these engines - that just plain run - and many for years with no maintenance - except when the owner does something they shouldn't. My new Stihl chainsaw ran right out of the box from the dealer - it has cut up about two cords of wood so far - and I haven't had to change a thing. The aircraft engines we buy are about the same - they should run forever when set up - and set up isn't that hard. Yes, you need a good spark plug - whenever my John Deere starts to act up, I put in $4.00 worth of spark plugs and off it goes for another year. Same with my 3W or BME or DA. Use fresh fuel with the proper oil mix. You need to understand how the low and high needles interact - and then set them using a tachometer. You would be amazed at how many fellow modelors have been surprised at how far off their ears are from my tachometer when I pull it out - gas and glow. One you have an initial set, make adjustments slowly. Yesterday, my 3W80 was rich at full out - 1/16 of a turn brought it right in where it should be. Just take it slow and one step at a time and you will get it running where it should be - that BME 50 is a real jewel - my buddy has two of them on a DC3.

Dan