It's not the battery as much as the starter. They are rated for different sizes of engines. My old starter was rated for up to a 1.80 and worked great on my little 7 amp gell cell flight box battery. I have a cheap heavy duty starter now rated for up to 1.40 engines and it fires up my YS 1.10s and 1.20s without problems. I can even roll over my 1.40 gasser with it on a 7 amp battery as long as the battery is charged up. Make sure your engine is making that squishy squishy sound before you try to fire it up too, YS wants the pressure pumped up first and they roll over easier when wet, that squishy sound.