Tim, both the 25 & 33cc weigh about 4 lbs. The 25 is in a bridi old timer stiz running a 16x6x10 zinger prop weighs under 12 lbs. The 33 's are in a Sig 1/4 scale cub & a scratch built from plans from AMA. They both are running 18x6 zinger props. All of my conversations run stock ignition. I uploaded a pic. of the scratch one.