Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I bought a tachometer from eBay for $23 including shipping and what a total junk it was (http://cgi.ebay.com/Tachometer-Hour-meter-2-4-Stroke-Small-Engine-Spark-/120689310104?pt=LH_DefaultDomain_0&hash=item1c19a4b998  I got mine from a different seller and was able to get a full refund but what a junk - you can buy a nice bottle of wine for $20 so don't waste your money on this model.

MN_Runner,

   I bought three that look exactly like that for about $18 with shipping.  There are a few variations.  Some have a single lead, others have a ground clip.  Some have a potted battery and others have a replaceable bat.  There was no manf listed for mine in the paperwork it came with.  On the boxs was Hourmeter-HM011.  It's an hourmeter and tach.  Since there is usually only an import company listed rather than a maker it's tough to say just who or how many manufacturors are making these things.  It's impossible to tell what's inside each one that looks the same.

   Mine sometimes reads double (harmonic) or half of the expected rpm.  A few times I've had to reset from 2 to 3 (once every resolution and once every other revolution).  It's more stable when the machine is just running standing still.  When under load engines are not so stable so having fluctuation when sampling is understandable.  There's the sampling up date time on the meter and the engine changing slightly as it's clearing more or less snow.   When running fairly smoothly the gage generally settles down.  I'm not sure if a more or much more expensive meter would do better.

   Part of the problem may be noise.  There is quite a bit of vibration,  Taping the wire onto the plug wire may help.  Although I have not done it yet, getting a resistor plug may improve readings. 

   A couple cheap lazer meters were picked up.  They do very well on a fan with a piece of reflective tape on a blade.  They have a very hard time sensing impellers and augers.   That's probably due to shaking.   

   Does yours have a manf listed or a model number?  Mine came in a white box with a single 4 x 10 inch sheet with two sides filled with directions.

Haveing the type with a ground lead may work better.Mine has the ground and always reads right.It just has a lag on the rpm

refresh rate.I just set the proper fireing rate and have never had to reset it again.My bet is most likely they found adding a

ground made it work better

My hour-meter is a single wire that needs to be looped around the sparkplug coil wire.  If I set the unit for a spark every two revolutions (Setting 3 for 4 cycle engine), I get double counting - at low throttle - my rpm is around 4000.  If I set for a spark every revolution (Setting 2 (which is also a factory setting) and for 2 cycle engine), the RPM seems more realistic.  The RPM reading varies - having a ground wire probably helps a great deal but my tachometer does not.  It came in a white box (LxWxH of 3x3x2) with a "HOURMETER-HM011) and a copied instruction sheet.  What it bothers me is that at the 4 cycle setting (spark every two revolution) - I get double counting and the RPM looks more realistic at 2 cycle setting (spark every revolution).

2 is the correct setting i found that out on my old L head Tecumseh.And the rpm is correct as the spark plug does fire on compression and exhaust

strokes.Keep in mind a lot of 4 strokes do fire plugs like that so the same setting 2 works for 4 and 2 stroke engines.The tach is only as good as the way you have set it up !    PS I have tryed to remove the picture i put in this thread as it is to large but i can not

figure out how to do it.Sorry for the screw up!

In order to properly use one of these tachs, it must be established whether the ignition system uses wasted spark or non-wasted spark.  It's less expensive to make a wasted spark system because the ignition fires on every stroke.  Simple and easy with no adverse consequences.  I'm not aware of too many small single cylinder engines that don's use wasted spark systems but I'm sure there are some exceptions.  

Borat,

   I would think these simple tachs count as they say and are not doing anything special for one lung wasted spark systems.  That would make 2 the right setting. 

   I have gotten good and bad readings using 2 and 3.  The wire lead and it's routing could have an effect bothering the gage.   The same for whatever metal is near the routed wire.  Meter fluctuations may be due to engine fluctuation.  The vibra tach is not all that steady when taking readings.   Any slight movement in rpm would cause a small period of sense and then up date so if the engine is not so steady then the readings will be all over the place until it settles. 

   MN_Runner.

     It might be worth while to try the tach on your car to see if it reads better. 

     It looks like we have the same meters.  Relics has the ground clip.

    One of the reasons I got the meters was to get the rpm dip under load for various engines.   That's tough on the meter as the engine is changing rpm all the time when working hard. When an engine runs loaded but fairly steady the readings get steady.  They are not so good at instentanious updates when an engine swings.

I have a Fluke multimeter, what can I use to take RPM readings? 

I am not sure if you can use Fluke to determine RPM.  It is great for checking for short or open circuit or simple current/voltage measurements.  I bought a tach-hour meter to suffice my simple curiosity and nothing more.  I don't really need to know the RPM that bad since I may not change anything in the end hence minimal value of having one.

aa35,

   Can't happen unless the sensors and circuits are built in your model.   For yours to read RPM it would have to have a front end attachment which sensed and converted rpm to ohms, amps or voltage which your meter can understand.

MN_Runner,

    03 is what worked today.   It took a while for the thing to read as that specific engine takes quite a while to stablize.  Also it has a very slight hunt which I think is just enough to give the meter trouble.  For the meters to sense well it probably requires the engine and especially the carb to be in top shape to reduce even minute hunting.  Most engines which are running well have a slight hunt.

Hey  trouts,

When the temperature goes up a little I will try it on my Honda lawnmower as it has a fixed throttle speed around 2900-3100 rpm.  So if it reads near 2900-3100rpm then the tach is good.    The setting 2 seems to be more reasonable than the setting 3.