I'm not sure there were any bugs as such. I've had the older SPE 40 now going on nearly 2 years and apart from CDI problems the engine has been VERY reliable. The original Melody CDI systems were a bit of a let down but I replaced mine with an RCXL type - been ticking over ever since. I have a mate with the newer SPE43 and it goes like the clappers. Mine is mounted in a Seagull Extra 260 which calls for a 160 2 stroke. The SPE40 pulls it around fine - not quite 3D but pretty good. I think you will find most people have had a good run with their SPE engines - then you will always find a few that havn't - but thats with everything.