Review: Oppama PET-304 Tach

If you want to objectively tune or troubleshoot your small two-stroke engine, you need a tachometer (tach). There are many options to choose from, but I choose to purchase Oppama Industry Co., Ltd.’s PET-304 since I saw some prominent lawn and small engine youtubers using it. I believe it’s also the same the Echo branded one, just without the Echo brand name stamped on it. Finally, I was also able to find a good deal: less than $62 shipped from Weingartz.

What’s in the Box?

I could tell you, but I’ll let my pictures do the talking:

Caption: This picture posts upside down for some reason.

Specifications

RPM Range: 100 to 20,000 RPM

Accuracy: plus or minus 10 RPM

Accessories: Inductive pick up lead (included)

Weight: 29 grams

Updated readings: Every 0.5 seconds

Wired or Wireless?

When watching youtube videos of engine tachs, people simply hold the tach up to their engine and take a reading. But when searching online, most of the tachs have wires that attach the tach to the spark plug wire.

To clear up any confusion, you can take RPM readings with or without the wire. I choose to use the wire to get what I would presume would be more consistent readings. So instead of the holding distance varying depending on the engine and spark plug placement, I can just use the wire to make things more straightforward.

Caption: This is how the instructions say to connect the wire to the tach.

Attribution: Author’s Own Work

How Does it Work?

Exactly how you think it would. Just clamp the wire to the spark plug wire (ignition lead) and the tach will do the rest; it even turns on automatically when it’s close enough to the engine (1/2” to 12”) or is connected to the ignition lead.

There’s also no accessible battery compartment. Apparently this isn’t designed to have its battery replaced. Initially this bugged me, but the battery should last 20,000 hours. To put that in perspective, that’s more than 830 days of continuous use.

Here’s a picture of me taking a reading on an Echo PB-251: 

I also used it on my other machines, including my Echo CS-271T top handle chain saw and my Bolens BL110 string trimmer and it worked without issue.

Other Notes

Based on the pictures in the instruction manual, the PET-304 appears to be water resistant, so you can presumably use it in the rain without issue. However, the instructions also say to avoid getting the inductive lead wet or letting it touch anything during a reading. So if you want to use this in the rain, you’ll need to do so without the inductive lead. There is also a hour-meter function that keeps track of how long it’s been used.

Conclusion

Anyone in the market for a name brand, high quality tach should consider the PET-304. It’s a bit pricier than some models, but it’s a great addition to anyone’s toolbox or workshop.