I got a Tiny-Tach non reset Model 2C, Got it from the manufacture, Design Technology, Inc.
designtechnology.com or tinytach.com
$36.95 + 6.97 shipping = $42.92 total
The reset model is the same price, but I want to be sure I don't reset the hour meter in error and loose track of engine service time.
I installed it on my Honda 4 stroke, but will work on my 48cc two stroke as well.
The four strokes fire on every revolution just like the 2 stroke do. The reason is there aren't any points so the plug fires each time the magnet passes the coil, which is every revolution.
It would be nice if they came in a round case like a speedo, but they are intended to be mounted to the engine. I have it mounted to a quick release flashlight handlebar mount. I put plugs in the two wires so I can take the tech off when parked along with the computer and lights. Out of sight, out of mind.
The hour meter reads 24/7 when the engine is off. The batteries are not replaceable as the cases on all the brands I have seen are potted. The battery is supposed to last around 5 years.
It is really convenient as it let me know just what was happening. 2250 RPM idle, 2500 RPM clutch engage. Around 4500 RPM at 20 MPH and 5000 RPM at 25 MPH. That is where I wanted to run the engine for max torque. Obviously there are a lot of RPM above for higher speed, but 31' per second is fast enough for me to hit anything. )
Jim