A fellow club member has a YS 140 & it has been no end of trouble, a real PIA. I find this curious as the pattern flyers love them & competition flyers cannot afford unreliability.

This is the Saito I suggested, two cylinders in line so it's easier to fit in long thin cowls (like yours). I'm not a Saito groupie, I just use what works which is usually OS but most people I know with Saitos are delighted with them. John.