I am currently using a Globee tach to tune my 4-strokes included a YS. Small movements make big changes in rpm and the repeatablility is not really good. Any other inexpensive tachs that are better?

I've had that one and a Hobbico Mini Tach. The Hanger 9 DVT was the best tach I've had and it would still vary a couple of hundred RPM all by itself. It was destroyed in a car crash. I built my first frequency counter from a Heathkit in the 70's and it was a lot more stable than these things. Maybe I'm expecting too much. Fromeco is supposed to be coming out with a revamped TNT tach for $95.00. If I hear from the first time users that they are as stable as the original TNT that is going to be my next buy.

Try pulling off the circular piece from around the light dependent resistor in the front and painting the inside black. I used a marker and it helped somewhat.

John

Thanks for the info. Actually, I would be happy with a few hundred rpm variance. Usually more like 1k-1.2k

Any optical tachometer can be "spoofed". You do need good light and a contrasting background because the tack counts the "flickers" it sees when the prop goes by. Trying to tach a black propeller when the background is black in shade or cloudy conditions can cause a problem. Trying to tach under a tree where the shade varies and moves around will fool the tach.

The best place to tach the engine is from behind the prop next to the cylinder. This gets it a few inches behind and in the outer 1/2 of the propeller arc. You may have to angle the tach slightly to get a stable reading.

In direct sunlight, there should be no problems getting a reading, but most optical tachs don't work well if they're more than 4-6 inches away from the propeller.

Thanks Bill, I will give it try this w/e

Fixed a friends Globee by painting the entire top half of the unit flat black. Found this was needed to stop ambient light getting to the photocell. Be sure to mask the photocell. Good luck, red

Forget the accuracy of the Tachometer. Behind the prop is the only SAFE place to do it!

Ed S

Does painting the prop help ?