What Clayton said unless your latches are set too tight, so it wouldn't hurt to check the pony rpm which should be 3000 at the flywheel, including under load with the compression on the main engine. Within 100 rpm / ideally 50rpm is probably close enough but if you can get it dead on, that's ideal. If your governor hunts, you might have to average the low and high readings. I don't know how fast Cat ideally wanted it to spin in order to delatch but I can't imagine it would be more than about 3500-3750 pony rpm. Maybe someone on here has specs from Cat? Set the rpm if necessary unloaded, then set the latches after checking unlatching performance. One other thing to note is that if the main engine doesn't fire up solidly / kind of stumbles along, the pinion may not unlatch and this will prevent the main engine from starting, so if you find this happening, disengage the pinion clutch so that the main can take off and unlatch the pinion. This happened to my buddy's HT4. The other problem that can affect latching is when the latches become worn and "slide off" the stop's shoulder that they latch on to. The fix itself is easy (just grind them perpendicular) but getting to the latches to reshape them can be challenging if you don't have a two-piece clutch shaft (after serial # 5U13273)