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.

Project: Partial Restoration of the Echo PB-251

I love yardsaling and shopping at thrift stores and pawn shops where I can usually find a really good deal. For example, I got an operational Echo CS-271T for less than $85 out the door at my local pawn show (they were having a 50% off sale). Over the next few months I’ll take a close look at its condition to determine how great (or bad) of a deal I got. I will probably do a separate blog post on that chainsaw.

But for now, I want to discuss the Echo PB-251 blower I picked up at a yard sale for $5. Given its age, it was in decent shape. But it needed “a little bit of work” according to the seller. In this blog post I will share the rebuilding/refurbishing process of this blower.

In case you’re wondering, this is very similar to Echo’s current model, PB-250LN and they both have very similar specs: 142 mph v. 137 mph and 386 cubic feet v. 391 cubic feet.

Background

I already had a Stihl backpack blower (BR 600 Magnum), but wanted a handheld for cleaning up grass clippings from my driveway (it’s annoying to lug around the backpack blower to run it for less than 5 minutes) and to increase my leaf blowing capacity in the fall. I saw some Stihl handheld blowers for around $65 to $90 at a few local pawn shops and thrift stores, but I wasn’t ready to pull the trigger on those for that kind of money.

Condition of the Echo PB-251 at Purchase

A picture is worth a thousand words, so I’ll begin by simply showing you what the PB-251 looked like when I bought it. It did come with the tube, but I removed it to take better pictures.

At first glance, I knew it required some muffler work and a new air filter. But besides that, I wasn’t sure what else was needed.

Did it Run?

Yes, yes it did. I reattached the muffler and it started up no problem. It also ran pretty well and was immediately useable as a blower. What I didn’t know was if it was running at its full potential. My only other gas powered leaf blower is my Stihl BR 600 Magnum and this handheld obviously could not compete with that backpack blower. But how was the PB-251 currently running compared to how it should be running? I did some digging and testing to figure that out.

The Muffler

The muffler was fine, but was missing the spark arrester screen. I bought an OEM replacement and installed it without a problem.

I also purchased two OEM bolts to hold the muffler cover on the blower (there’s a picture of the cover installed later in this blog post). At purchase, these bolts were missing and that’s why the above pictures of the blower don’t show the muffler cover (it wouldn’t say on).

From a performance perspective, this wasn’t necessary, but from a safety perspective, it was. I had already burned by finger once when I accidentally touched the hot muffler.

Caption: The bolts and spark arrester as they arrived from Echo’s parts supplier.

Attribution: Author’s Own Work

Compression

There was definitely some compression when I pulled on the rope, but having no prior experience with the PB-251, I had no idea if the compression was where it was supposed to be. My compression tester showed that it had about 120 PSI.

Caption: PB-251 compression reading.

Attribution: Author’s Own Work

Based on my online research, this is in the ballpark of what I should be getting. If anyone disagrees, please feel free to share by commenting.

RPM

According to the manual, the idle RPMs should be between 2,700 and 3,300, with wide open throttle at around 6,700 to 7,200. I tested this PB-2251 using my PET-304 Oppama tach (I’ll write a review blog post on this nifty little piece of kit soon) and measured 3,800 RPM at idle and 6,400 RPM at wide open throttle. I know these RPM readings don’t perfectly reflect an engine’s performance, but I wanted to get an idea of what I was getting without doing anything to the blower.

Also, the fuel I was using was old, I mean really old. It was mostly ethanol free 91 octane gasoline with Stihl Ultra 2 stroke oil from last fall (it’s about a year old during testing). So I would expect my numbers to be a little bit low.

Caption: RPM reading at idle before doing anything to the blower.

Attribution: Author’s Own Work

Cylinder and Piston

Given the compression and how the PB-251 ran, I was expecting the cylinder and piston to be in good shape. Based on my eyeball check after removing the muffler and spark plug, both looked to be in good shape with no signs of scoring. 

Spark Plug

Here’s a comparison of the old and new spark plugs. Looks like the old one’s been run a bit rich during its life.

Caption: The new one isn’t exactly like the old one, but it works.

Attribution: Author’s Own Work

Air Filter

The air filter was nasty and needed changing.

Caption: Can you guess which filter is the old one and which is the new one?

Attribution: Author’s Own Work

What’s interesting is that after installing the spark arrester and new spark plug, my wide open throttle RPM dropped to 5,800. My guess is that the spark arrester screen is largely responsible for this. But maybe the spark plug to? I’d be interested to hear any comments from anyone else on this issue.

After putting in the new air filter, it went back up to 6,400, so it looks like the old filter was as clogged as it looked!

The Rebuild Kit

In case you’re wondering, I got the new spark plug and air filter from some aftermarket seller on Amazon or eBay. It came with other things too, like a new carb, purge bulb, fuel filter and fuel lines. But since the blower seems to be in fine shape, I didn’t see a need to do the work of replacing those items.

Caption: In case you’re wondering about the kit’s number.

Attribution: Author’s Own Work

Caption: Here’s what’s in the box.

Attribution: Author’s Own Work

What Did it Cost?

Caption: The PB-251 with the muffler cover on it.

Attribution: Author’s Own Work

I spent a total of about $22 total on this blower ($5 for the blower and $17 for the rebuild kit). Since it works well enough already, I probably won’t do anything more to it. But this was a fun and easily little project that got me what is effectively a new handheld blower for less than $25.