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.

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.