Small Engine Tachometers

[38racing]

Back here again. I have 2 of the tiny tach knockoffs. Thought I was getting correct rpms but I have connected an alligator clip to the leads and clip it on plug wire instead of wrapping and holding with clothes peg. Recently I was suspicious of the readings and found they were not the same on both. Up to 1k different. And readings and my ear didn't agree. This was on pushmowers. I'm wondering if it's the clips. Also I have both units together in a container. Maybe they interfere with each other? Going to test them again by separating and wrapping. Watched a video where the guy inserted an inline tester to make his connection because plug had metal cover that he thought affected the pickup. Has anyone used the rotary 15344. Appears to be what my supplier is offering for about $100 cdn.

[bgsengine]

if I was you, I'd find, and invest in, a treysit Sirometer (vibration tach) and learn to use it.. Briggs and Tecumseh both offer their own branded versions and are always handy to have if you do any electric motor or diesel work at all.. and you can always fall back on that if you suspect an electronic reading is "off" (I seem to recall rotary had them too at one time) Keep in mind the tiny tach (and knock-offs) is only reading inductive pulse from plug wire so it counts each time the coil fires.... SO you also need to know if the engine you are testing is wasted spark ignition or not.. example: a Kohler K series with point ignition would show you 1800 RPMS at a true 3600RPM because their point ignition fires off the camshaft instead of the crank, if the meter was designed to work with waste spark (and 2-stroke) which fires every crankshaft revolution.. or else the waste spark ignition would give you a doubled RPM reading if it could read the kohler RPM right (I remember the programmable tachs I had 25 years or so ago you could move a little switch to handle both types.. )

[RoyM]

If needed to check an engine where the points are activated by the camshaft such as a Kohler K series double the reading. If it reads 1800 rpm the engine is turning 3600. I have the Stihl tach which while not cheap is very accurate. A lot of the cheap ones are slow to respond to speed changes so can be hard to read as the display isn't stable.

[creia]

Back here again. I have 2 of the tiny tach knockoffs. Thought I was getting correct rpms but I have connected an alligator clip to the leads and clip it on plug wire instead of wrapping and holding with clothes peg. Recently I was suspicious of the readings and found they were not the same on both. Up to 1k different. And readings and my ear didn't agree. This was on pushmowers. I'm wondering if it's the clips. Also I have both units together in a container. Maybe they interfere with each other? Going to test them again by separating and wrapping. Watched a video where the guy inserted an inline tester to make his connection because plug had metal cover that he thought affected the pickup. Has anyone used the rotary 15344. Appears to be what my supplier is offering for about $100 cdn.

The China-made knock offs are crap. Get yourself an original "Tiny Tach". I agree with Brian on the Treysit vibration tachs. We have one made by Tecumseh. There is a bit of a learning curve to be able to use it accurately, but once you have learned they are a great tool for a reliable quick check for rpm.
Michael

[Arkie]

I tried the lower priced digital and mechanical tachs and finally knuckled down and bought a PET-304 about 4 years ago from BGS engines on ebay.

I use it mainly on chainsaws where I need a accurate tach and a fast re-fresh rate when tuning the carbs, it has a really fast refresh rate, I've never had to replace the replaceable battery.