I recently built a racing lawn mower and I removed the governor so I can get some more speed out of it but I need to install a tachometer so I dont blow the engine. Can anyone help me out? How would the tachometer hook up to the engine?
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February 15th, 2010 at 8:23 pm
tachs for racing lawn mowers are as costly as you might expect:
digitronusa.com can help you in locating a pro model if you are interested.
the basics of tachs for lawn mowers differ based on a 2 cycle or a Briggs & Stratton engine. a 2 cycle engine produces more noise at the spark than a B&S engine so when connecting a tach to a B&S engine you should coil the sensor wire around the spark plug in order to make sure you get a good enough signal.
the other major connections are the ground (directly to the engine) and the hot lead which I would imagine will be connected via a fusible link or fused connection to protect the tach.
erratic readings can be caused by poor signal so make sure you follow the directions for installation based on your engine type.
troubleshooting tips by DigatronUSA
Sensors checks:
Damaged or incorrectly installed sensors (leads) are often the cause of instrument problems:
Instruments getting a tach signal from the spark plug wire: For a Digatron instrument to work correctly the instrument must be receiving a good tach signal. Tach sensors are small antennas that pick up the energy radiated by the spark plug wire. Without a strong tach signal the instrument will give low erratic tach readings. With no tach signal, the instrument will not record for more than a few seconds and will power itself off. Check your tach sensor installation:
Briggs & Stratton engines: B&S engines, and similar 4 cycles, have ignitions that produce weaker signals than other engines. To receive a strong enough signal with these ignitions, the antenna needs to be longer. The easiest way to do this is to spiral the colored wire (antenna) down the spark plug wire.
2-cycle engines: Generally strong signals are produced. Attaching the end of the tach sensor to the spark plug wire should be sufficient. If you experience low erratic tach readings see A.
Instruments getting power and tach from the lighting coil: Make sure you hook the black wire of the power harness directly to the engine, and hook up the red wire with the fuse holder directly to output of lighting coil before the regulator. The power harness uses a ½ amp fuse. Be sure the power harness is connected to the connector on the back of the instrument.
* Loose sensor connections to the instrument can cause erratic or spiked readings. Placing a piece of tape on sensor connections can help ensure a strong connection.
* Broken and nicked sensors, and sensor wires, can cause erratic readings to all functions on the instrument. Replacing one or all of your sensors often solves the problem. Careful installation, and protection of sensor wires with plastic tubing, is essential. Damaged pigtail wires or sensors may give erratic readings, abnormally high readings, or a “00″ reading.
* Keep your temperature and tachometer leads separated by at least 3 inches. Do not tie-wrap or tape leads together, as this can induce noise into the instrument.
* Route the leads as far away from the coil as possible.
* Install the tach lead on the plug wire at least 2 inches back from the plug boot. If you still have a problem, try a different location on the plug wire.
* Be sure that all sensors are connected to the instrument and that all connectors fit together snugly. If you are not using a temperature function, you need to use a shorting plug on that pigtail. Contact Digatron for shorting plugs if you will not use one or more of your temperature functions.
* If you are using an exhaust gas temperature sensor, make sure it is grounded.
* You can run your leads through separate sections of fuel line to protect them from cuts and abrasions, but it will not shield them from ignition noise.
* If your MPH or Jackshaft is erratic check the distance from the sensor to the collar (or selected trigger). An 1/8″ or less is the ideal setting.
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Timing checks:
* Is the beacon on?
* Are the beacon batteries low?
* Is the beacon still on the track? Did someone remove it or turn it off?
* Check that your Digatron instrument is programmed to recognize the code the beacon is transmitting or that all codes are set to none and you are using the delay feature. Check your instrument setup instructions.
* Did you reconnect the beacon receiver to your instrument after downloading to your laptop?
* Is your beacon receiver pointed toward the beacon transmitter?
* Is the beacon receiver plugged into the correct connector on the back of the instrument? Attach the beacon receiver wire to the lap connector on the instrument and mount it on the vehicle so that the beacon signal has a clear path to the receiver.
* Have the beacon on standard power if it is within 10 to 25 feet of the instrument on the vehicle. Set the beacon on high power if over 25 feet from it. Standard power conserves batteries.
* Your vehicle should be at least 10’ from the beacon transmitter on the track. Beacon signals are cone shaped and if you are too close to the beacon you may miss the signal or intermittently pick it up. The faster the kart the farther from the beacon transmitter it should be. This ensures the beacon receiver has time to pick up the beacon transmitter signal. The instrument has to be in the beacon transmitter field for at least 1/50th of a second to identify the code. See Diagrams below for a graphical representation of the Beacon signal.
* Beacon transmitters should be at least 25’ apart. Beacon signals are cone shaped and can overlap if beacons are too close. This may cause the instrument to have trouble picking up a lap signal. For a safe distance apart, measure the distance from the kart to the beacon, and multiply by three. This is the recommended distance between beacons for consistent operation.
* Multiple short laps may be caused by multiple beacons on the track transmitting the same code your instrument is picking up. If you have a 50 series instrument change the code on your instrument and beacon or change the delay number in the instrument. If you have a 40 series instrument enter the number of seconds to ignore beacon signals after you pass the first one. See your setup instructions.
* Direct sunlight into the beacon receiver will reduce it’s sensitivity and can cause it to miss a lap. Make sure the receiver is installed with the overhang on top. If the rising or setting sun is pointed directly into the beacon receiver, set the beacon transmitter on high power.
February 15th, 2010 at 8:39 pm
Yeah I’ve got one of these also, the engine redlines and I can push it as far as I want, there’s no governor. I do it for my business so I have the extra power if I need it, but you really need to check into a tach specifically made for this, they do sell them for lawn mowers.
Not sure where you might find one, but here’s one I googled up:http://www.amickssuperstore.com/ENM_2_st…
February 15th, 2010 at 9:05 pm
The tach is normally tied to the ignition coil, I believe on the NEGATIVE side, but you’ll need to confirm this. It may depend on the tach itself. But usually it is the coil ground side it attaches to.
February 15th, 2010 at 9:09 pm
Hey,can you bring your speedy lawnmower to my place and cut my grass? I will pay you by the hour.
February 15th, 2010 at 9:47 pm
Purchase a tach and a creativ mount. You will have a battery plus wire, a ground wire, and a wire going to the negative on the coil (sensor wire). The trick will be finding a tach that will operate on your number of cylindeys (probably one or two as opposed to 4, 6, 8), I would look towards motorcycle tachs.