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.

Why do you feel it was junk? I have the same one from him and its been fine.It shows 7 hours on it now with no problems.It has a slow rpm refresh rate other than that its just fine fine.

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.

I guess the ground wire must make the differance with one of these tachs.You should be set on 2 at all times 3 should not be used at all to see accurate rpm readings.Did you guys look at the lead comeing out of the tach and make sure no white wire is included

under its plastic covering? Who knows there could be one there.With todays light snow i only ran my machine between 3000 and 3200 rpm..I did push some snow to the sides of the driveway to set up a load for the blower.Than i would go to 3600 but even than i would only drop to 3450 or 3500.I find my engine hunts very little.And than its really only when going into a good sized load.I

 must feel the govenor doing its thing for a second or so                                                                                                    a second or so

It is a multi-stranded copper wire without any other electrical wire (i.e., no separate ground wire).  I was able to open the back of the box and thought about adding a ground wire but I do not have schematics for the printed circuit board.  I could find it using fluke meter but it is not that important. 

I have had the back off mine to.I will look tomarrow and see just were the ground wire goes.I will get a picture to

and see if it looks the same as yours ! Although i would think it could go to the ground side of the battery and work?

Relics,

    I'd be interested to know if yours looks the same inside as one MN_Runner posted. 

     The tach was put on the car which has an RPM gage.  The gage was set on 3 and tracked with the car readings over the range of 700 to 3000 rpm.  At first readings around 2000 were ok but lower and higher off by quite a bit.  After about 4 minutes of warmup the readings tracked the car gage. 

   The wire sense lead was wrapped 4 times around the plug wire and taped inplace.  It was also run straight which I think helps.

   The post time is about a half a second after a speed change but seems to take 1-3 seconds for it settle and get a correct reading.  The posted incorrect speeds are always in the right direction and between the reading moved from and the current rpm.  The gage is probably taking several readings and averaging so needs a second or so to get a tight group for the right average after the speed change is complete.

  It did much better than when connected to the snowblower.   Part of the problelm on the blower might have been not having a straight run of wire and the wire field interfearing with itself.  Also, speed changes on a blower engine are not that smooth compared to a car.   

Well here is the inside of my tach which showns the location of the white wire.Which is used as the ground wire on the 2 wire tach.

For some reason? the picture would not post.

Here is the picture !

relics,

Thanks for the picture - I can clearly see the two wires on your circuit board.  I just tried it on my Honda lawnmower and the rpm reading is reasonable.  I was getting 2950-3000 rpm, which is consistent with the manual.  However, the correct RPM reading came at the "2" setting (1 spark every revolution) instead of the expected "3" setting (1 spark every two revolutions).  So my cheap tachometer needs to be at "2" setting to read correct RPM.

2 is the correct setting.Its the same on my old tecumseh 8HP.These engines do fire everytime.As stated already its a waste spark system.So the plug fires every revolution.An for sure your tach is giveing the right rpm.I think the ground wire just makes the tach most likely work slightly better.Maybe a slightly faster refresh rate who knows? But for sure these tachs are accurate.I have used mine for over 8 hrs and its just fine.I find its a real plus to know my rpm.Also running at max rpm i can be sure i am within a safe range and not going above (3600rpm)

Just for reference;

It looks like all NM_Runner and Rlics boards are similar to mine, all HM011's but all different revisions.  Mine's from 5/10/2010.  Relics is stamped 2010, has different parts and seems newer.   Mine has GND at the open pad by the wire input lead so I added a ground there and drilled an outlet hole for the ground wire. 

It's now operating well on 2 and much more stable.   ( I have three of these).  They were not so stable before and would take a lot of time settling.  Often they read better in 3 than 2.  I had tried a few different wire leads, shielded and non shielded.  The length and type of wire would cause readings changes.  They had to be frigged and fragged with to get good readings.  Often they would read well in a small range rather then read well over the whole range of 700 to 3600 rpm.  They are noisy.  If I put an unconnected meter close to a connected meter the unconnected meter will display rpm readings. 

The upshot is there are a number of rev's of this board out there with various features.  The single wire will work but has to be messed with to get reliable and consistant readings.   The grounded version of the HM011 is the one to get. 

  

Thats great Dave now we know the ground is needed to make the tach work correctly.Did it take you long to update it with the ground wire? It also can be seen the batterys can be replaced with a little effort of removeing glue.Although i would not be surprised if there is some type of set up procedure if battery power is lost.?

   It will probably reset by itself with a bat install.  There "reset" printed on the board so worse case those pads could be messed with. It would be nice to have a schematic.  The two big chips are a 7400 series which is a simple D flip flop and probably takes the S1 and S2 inputs.  The other is an 8 bit risc chip.  The data sheet for it is online.  It should have a reset pin which usually is pulled to ground for a reset.

   The back cover comes off easily and the soldering is simple with a pencil tip soldering iron.  I put a short wire on for ground and will put a perminant wire on machines so the meter can be removed easily.   The case is not brittle so easy to drill without cracking or breaking the case.  The back cover also popped off easily with a knife. 

   Mine was advertised as "replaceable battery" and also listed as potted.  It's not potted and there's no batter holder or compartment as I expected.  There's probably a lot of ticked off people who bought the single lead version.

   On a closer look your board and my board are very different.

Why not just ground the shield of the "single" wire?

On the single wire units are a single "wire", no shield.

I did try miniature coax starting a few inches outside the case which did not help.  It would have been better to run the coax shield as the ground inside the meter and tie the other end to the engine but I did  not want to solder the shield in such a tight spot inside the meter.

RF can be very weird.   It might be useful to try an R plug.  It's possibly it might have cured the meter

Messing with the tach's again. The batter crapped out last year so replaced it today so some observations for tach owners like the HM011 types. The back of the case can be pried off with an Exacto knife and the bat unsoldered. The harder part was gluing it back in place to hold the bat to ground which is a very iffy deal as the bat is only pressed onto a ground on the board not attached. It's then held in place with silicone or epoxy. A messy deal with epoxy as it's conductive so a tricky install. Before buying the bat it got tested by putting two 1.5's in series which worked. So an alternative to installing a new bat is getting a dual 1.5 AA holder, run the wires through the case and solder them to the lithium batter post and ground.

    Tach mounted to Murray SS.  Pretty easy...a piece of flat stock drilled and bolted to the carry handle mounted with velcro.  For some reason the response time on this engine is much better than prior use on 7 and 8hp 4 cycle engines.  Hopefully it will catch the sag when running booted rev's and loaded.

If I remember right,  the reset on the board is for awiring of a switch to reset the "hobbs" or hour meter... On some units there is a button built on the case, to reset for maintenance or serviceing needs..

I had the "Tiny-Tach" made unit for 12 or so years before the battery took a dump,  never gave me a lick of problems...   If you are doing repairs or maintenance/ tune work,  there is a nice unit made that is total inductive with no wires...  It has a fast processor and is good to 5 rpm change in speed.. I can't remember the name (sorry)...  but you had to hold it within 1 foot of the plug wire,   it was great of setting the high speed chain saws with the spark plug buried under some air induction cover..

Friiy

Has anyone connected an analog dial tachometer to their snowblower?  I'm asking since these little electronic tach have terrible lag and with small display which makes it difficult to read, wouldn't an large dial tachometer allow you to see it better and to get a feel at what your max torque or HP is occuring?