The tap off of the crank on the 140 DZ is just a pressure port which is timed by a passage in the crank. The regulator is actually mounted to the pump which is located on the pushrod tube. Refering to the plumbing diagram on YSPerformance.com http://www.ysperformance.com/prod140DZ.htm
there is no need, or place to install, a check valve on this engine. This appears to be a first for YS!

John