Hrkdrivr,

The YS pressurizes the fuel tank, so a stout tank - no Dubros or Sullivans - is required. The tank that comes with the UCD is pretty stout and I am using it stock with my YS120. If you have a concern, wrap filament strapping tape around the front, middle and back of the tank and put a nylon zip tie around the stopper neck and pull it tight once you have the stopper in place.

As far as the Cline, it works pretty much like the YS system only it uses carb suction to run the diaphragm instead of a pressure pulse like the YS. It pressurizes the fuel tank through a one way valve from the exhaust - on a 4 stroke and from the crankcase on a 2 stroke. If you go to http://www.billsroom.com/pcfs/fuelsysdesc.htm it will explain better than I am.

The YS is kind of supercharged because it uses the down-stroke of the piston to pressurize the fuel charge into the intake through a disk valve on the back plate. The air chamber on the 91 is to smooth the impulses for better operation.

Needless to say, with either system, you want a good tank that is not elastic.

Dale