For those who have considered making a simple U-tube manometer or a 4-port tube manometer for syncing their engine I'd recommend the following air flow restrictors be installed in the tubes.
https://www.motionpro.com/motorcycle/partno/08-0426/
These guys really tame the manometer and make it very usable.
Also I've seen some designs which use a PVC pipe reservoir in each tube above the liquid column for containing the liquid just in case one of the tubes is inadvertently disconnected from the engine. With these flow restrictors the pipe reservors are not necessary. The orifice is so tiny that only minute amounts of liquid would ever pass through to the engine.
The orifice diameter is less than 1/64". The overall diameter of the restrictor is 3/16".
https://www.motionpro.com/motorcycle/partno/08-0426/
These guys really tame the manometer and make it very usable.
Also I've seen some designs which use a PVC pipe reservoir in each tube above the liquid column for containing the liquid just in case one of the tubes is inadvertently disconnected from the engine. With these flow restrictors the pipe reservors are not necessary. The orifice is so tiny that only minute amounts of liquid would ever pass through to the engine.
The orifice diameter is less than 1/64". The overall diameter of the restrictor is 3/16".
Unfortunately, I don't think I can get them sent here in time for our Tech Day. 
