$10 ebay tach/hour meter instructions gibberish, this video actually explains it...............

[madprofessor]

Haven't been able to feel absolutely certain that the el cheapo $10 ebay (free shipping) LCD digital tach/hours/service interval meter I've been recommending to folks is set right for my Predator 212cc 4-stroke engine or not. The seemingly low rpm reading at a normal idle is about 800 rpm. Does anybody think that's about half of what it should be? What rpm's do everybody else's 212's idle at with nothing on the shaft?
Ran it wide open with nothing on the shaft for the first time (ungoverned and hotrodded) and didn't quite get 3600 rpm reading, about half of what my performance guy says it should reach at no load. The little scrap of paper with instructions for 2- and 4-strokes on 1- and 2- cylinders is kinda gibberish and unclear. Been fearing I may have it set for 2 sparks per revolution, or maybe some multi-cylinder mess.
Lotsssss of (misinformation) videos searching later, I finally found a proper video where the guy explains what to do with the buttons, how many seconds to hold it, what each number code means, etc., in a way even I could easily understand and see each step on his own meter. He sets it up for his motor, which like mine is a 4-stroke single-cylinder. Can't wait to get back to shop and check my rockers' heights to be sure I haven't got the cam one tooth off of alignment (how-to courtesy of my performance guy), then test my meter and reset it if needed. Link to 8-minute video below, hoping it helps somebody...............
Cheap Ebay Tachometer Explained - YouTube

 

[Hellion]

Never had any problem with mine except for the fact that they are slow {and cheap!}.

Make sure you buy the ones with the replaceable battery {removable battery cover on the back} and not the sealed ones
with the "lifetime battery".

 

[madprofessor]

Refresh rate note: I've searched countless tachs of many sorts online to see what faster refresh rate is available. Basically the only tachs that respond immediately to rpm changes are ones made for cars that require a separate 12vdc power supply.
Apparently all of the inexpensive self-contained-battery electronic tachs have refresh rates of a half second (like these $10 ones we're discussing here) to a full second. I'd pay more for a faster one, but adding 12vdc from my rechargeable power supply just won't work for me.
I'll be staying with the tach I've got now that the video removes any doubts.

 

[Thepartsguy]

Refresh rate note: I've searched countless tachs of many sorts online to see what faster refresh rate is available. Basically the only tachs that respond immediately to rpm changes are ones made for cars that require a separate 12vdc power supply.
Apparently all of the inexpensive self-contained-battery electronic tachs have refresh rates of a half second (like these $10 ones we're discussing here) to a full second. I'd pay more for a faster one, but adding 12vdc from my rechargeable power supply just won't work for me.
I'll be staying with the tach I've got now that the video removes any doubts.

Side note for tachs that are made for cars. They have a switch on the back. To choose from 4-6-8 cylinders. Even if you had the 12v from your rechargeable power supply I doubt it would read right.