30 notes from 1/4 sounds about right. My S1 will take 40 from the top of the red....

Does the tank have the swirl pot fitted? They sould have one as standard and if it's not there or damaged, then it will cause problems when you get down to 1/4 of a tank.

Had this happen on my Dad's Sapphire. It had the wrong tank on it which didn't have a swirl pot. When it was 1/4 or below, he couldn't thrash it because it would just hesitate and misfire.