digital tachometer

[David414 289]

 

I brought a cheapo digital tachometer which uses a  wire wrapped around the spark plug several times for its reading. I don't believe it is very accurate depending on factors such as how tight the wire is wrapped around the spark plug wire, the number of wraps used,  and the settings.

 

Can anyone recommend a better digital unit? I have seen a few that use tape adhered to a spinning object? I have a 1989, 414-8 with Magnum 14 engine.

Thanks,

[ebinmaine 67,610]

7 hours ago, David414 said:

I have seen a few that use tape adhered to a spinning object

I have one of this type. 

Seems to work well enough. 

It was MAYBE 20 bucks on the jungle site. 

 

There are literal hundreds of them for sale so I just chose one that had good reviews/less complaints. 

 

I've used it to check rated RPM of drills or electric motors and it seems to be fairly accurate. 

Mine came with tape. If you're checking an object that has a break in color like a shiny spot you may not need the tape all the time. 

 

[Skipper 1,788]

is it just to check the rpm once in a while, or is it to have a rpm gauge to look at when using the machine?

[Gregor 4,846]

8 hours ago, David414 said:

 

I have seen a few that use tape adhered to a spinning object?

This type is hand held. It does not attach to the tractor.

[squonk 41,155]

A lot of those Tachs get RPM of off the spark. If saying doing a Briggs with a mag, The points are driven off of the crank. So a Spark every revolution. A Kohler single is driven off of the cam so a spark every 2 revolutions. Most of these hand tachs don't have a setting for this. So the reading needs to be doubled

[Gregor 4,846]

3 minutes ago, squonk said:

A lot of those Tachs get RPM of off the spark. If saying doing a Briggs with a mag, The points are driven off of the crank. So a Spark every revolution. A Kohler single is driven off of the cam so a spark every 2 revolutions. Most of these hand tachs don't have a setting for this. So the reading needs to be doubled

MMmmm   Are you sure?

[Tuneup 1,433]

I have that 'bad' tach. We used to use a similar method to monitor the spark on cars. Wrap a wire several times around the spark lead and send it to a bulb to watch the cylinders flash. It's a matter of the number of turns and, yes, the closeness of the wind. My K301 took 6 turns, 2 ties and electrical tape to get a smooth signal and it's absolutely perfect. Trial and error. Too much signal = noise. I also have the tape variety - the one that looks like a gun. As long as plenty of that signal tape is used, it's OK. Good enough for setting the limits.

[squonk 41,155]

22 minutes ago, Gregor said:

MMmmm   Are you sure?

I bought this tach. 

 

In the instructions it explained how small engine point's are activated off of the crank. Which means the points open every revolution. and there was a setting on the unit for this. The Kohler single points open every 2 revolutions as they are opened by the cam which turns half the speed of the crank. There was no setting for this style. While checking the RPM om my K341 the maximum this tach would read was 1500 RPM when the engine was wide open and I knew by the sound it was actually at least 3000 RPM

[Gregor 4,846]

I was thinking of this tach. In past conversations, I think it was said the rpm number, actually had to be cut in half.

[David414 289]

9 hours ago, Skipper said:

is it just to check the rpm once in a while, or is it to have a rpm gauge to look at when using the machine?

Like to have a RPM gauge when using the machine.

[Gregor 4,846]

28 minutes ago, David414 said:

Like to have a RPM gauge when using the machine.

I always thought it would be cool to have an Tachometer also. When you think about it, with all the hundreds of thousands of garden tractors built, by hundreds of different manufacturers, I have never seen one. There must be a reason.

 

Except for @TractorheadBavarian Wheel Horse

Edited May 18, 2021 by Gregor

[ebinmaine 67,610]

1 hour ago, Gregor said:

, I have never seen one. There must be a reason

 

It's because for the most part you don't actually need one.

 

Most if not all wheel horses say by the book that with a hydro you should ALWAYS be at 3600 RPM.

You need to keep it at full RPM for the best cooling and fluid flow characteristics.

 

For the most part a manual transmission is the same.

The only exception I'm aware of is a sickle mower but I'm certainly open to correction from much more experienced people. 

 

 

Disclaimers.

Is that how I run my manual transmission tractors? No.

Do we pay close attention to make sure they're not overheating? Yes.

 

Do I think tachometers and other gauges look super cool? Yes. The more the better. But I certainly understand the keep it simple theory. 

[Gregor 4,846]

4 minutes ago, ebinmaine said:

It's because for the most part you don't actually need one.

My wife does not need one in her 6 cyl mini=van, but it's there. There is no debating it's not needed. It's just the cool factor.

[Tractorhead 9,064]

I don‘t stick it because it‘s cool, i use it to compare the Engine RPM under different Loads.

 

Even because the Predator and tillotson Engines that cheap, i like to know where are the Limits.

i tied few modifications on mine and hope it will last a little.

Idle RPM is at 1450 Full throttle is 3990, what can be easilly reached just by pulling the Trailer to the Dump.

On mowing a grassheight of 18cm it drops down to 3750 RPM but cut‘s like a charme.

the only dis is, it chews belts on this RPM‘s.

 

For me it is simply a tool to see what happened on the Engine.

 

Forgot to tell ..

 

it is a simple battery powred Digital Tacho.

it get‘s it pulses by a wire wound arround the spark cable.

Updaterate 0,5 - 1 Hz 

Got it‘s own Battery integrated

if Engine is off for more as 30sec. I goes to sleep mode.

If Engine ignits it woke up and count.

Servicelevel counter.

Cylindresetting can be changed 1-2-3 cylindre 2 stroke or 4 stroke.

Battery is replacable.

cost 4$ at the Bay.

Edited May 18, 2021 by Tractorhead

[elcamino/wheelhorse 9,326]

I think @Racinbob has a tach on one of his tractors or tried one. Maybe he will chime in with his experience.

[Gregor 4,846]

26 minutes ago, Tractorhead said:

I don‘t stick it because it‘s cool, i use it to compare the Engine RPM under different Loads.

 

Do you double the reading on your tach to get the correct number, or divide by 1/2. ? Or either?

[Racinbob 11,093]

1 hour ago, elcamino/wheelhorse said:

I think @Racinbob has a tach on one of his tractors or tried one. Maybe he will chime in with his experience.

 

Sorry but nope Eric. I use a handheld digital to set the no load max RPM and then just let the governor do its job. 

[Tractorhead 9,064]

1 hour ago, Gregor said:

Do you double the reading on your tach to get the correct number, or divide by 1/2. ? Or either?

I no there is a Setupmenu if you press more as five sec. The menu key.

than it blinks for 5 sec. a value after the 5 sec. Next value is shown.

to choose one value wait until it is displayed, press the menu key until it blinks 2 times, than this value is choosen.

 

Connection the spark wire isn‘t really connected into the system,

it is just a kind of Antenna to recieve the signalstrenght better.

originally it is stuck from down to top and back to down.

I found that the blank wire can contact the Tractors Surface

what makes dubious things because of vibrations.

So even on blank metal a short can happen. ( maybe your problem?)

 

So i reroute the original wire on it’s mountpoint  from top to down to top than pass thru the Hood 

( double insulated with heat shrink tube) and along the Throttle wire in front to the Sparkplug and turn it 5x arround the Sparkwire.

 

The reading is accurate and after each start i see the same Values.

Checked it against a contactless rpm gauge for Motorcycles i have also.

The Value fits after right Setup

depending if your engine has points or not,

or if you have a magneto you must sometimes choose 2 stroke engine to get right values.

 

Don’t hit the Reset button except on service, 

that will immediately reset all counters.

 

to switch between displaying of service interval or rpm gauge and hours

push short the menu key with a fingertip.

 

 

To go in Setup menu hit and hold (press) the menu key longer than 3 sec.

( on mine i must press it longer than 5 sec.) 

than you are in the Setup menu identificated by a flashing cl1in the display.

 

The Setup Menu

it begins with cyl. Setting

cl1 = 1 cylindre - 5 sec flash  if no key is pressed it switches over to the next item

cl2 = 2 cylindre - 5 sec flash. If no key is pressed it switches over to the next item

cl3 = 3 cylindre - 5 sec flash. If no key is pressed it switches over to the next item

 

st2 = 2 stroke engine - 5 sec flash. If no key is pressed it switches over to the next item

st4 = 4 stroke engine - 5 sec flash. If no key is pressed it Jumps out of the Setup routine.

 

reset to display

display shows now

rpm 0000 and

hr 0

 

if a Value is choosen, the system goes automagically to next setting

wait until all your points are marked, than press and hold the menukey for at least again 6-7 sec 

display switch back to main with the choosen settings.

setuproutine is done successfully

- It needs a little time for the first setup, but it rocks.

 

Edit- ah i found the Pict of my Tacho / RPM gauge  ( left side of the Steering wheel)

 

 

 

Edited May 18, 2021 by Tractorhead

[Skipper 1,788]

Ok, so for permanent mount, the easy solution is the type you have seen with the wire to twist around the spark wire. I have a tractor with that, and it doubles as an hour meter and service interval reminder. Little black thing from china. works fine, and it's on target with the rpm's. That's the easiest solution.

 

The "put a sticker on and shine the laser" type are good, but I have newer seen one for permanent use. only the hand held type. They might be out there though.

 

Then there is a ton of types that uses a tacho signal. Something from a old school single cylinder bike might work out of box, but not sure about it. Otherwise, if you want precise, there is the type where you mount a hall sensor at the flywheel, to give the signal, and it needs a magnet to pass it on each revolution. some drill or mill a slot, and set a magnet in the slot with epoxy or chemical metal. But remember, this signal is 100% correct, but still there is room for error in the gauge. And generally, the cheaper the gauge, the more room for error

 

So, if you do not want to mess much with it, the easy route is the "wrap a wire" type. Just make sure it fits your engine (number of cylinders and 2/4 stroke) 

Edited May 18, 2021 by Skipper

[ebinmaine 67,610]

4 minutes ago, Skipper said:

if you do not want to mess much with it, the easy route is the "wrap a wire" type. Just make sure it is for a single cylinder

I understand the concept of what you're saying just fine but I've never seen one for a single cylinder. Don't get me wrong there. I've also never looked!

 

If anybody has a link to one or could tell me how to find it, please PM me.

 

 

Might have been @BOB ELLISON that had a thread about attackometer a few years back

[squonk 41,155]

17 minutes ago, ebinmaine said:

I understand the concept of what you're saying just fine but I've never seen one for a single cylinder. Don't get me wrong there. I've also never looked!

 

If anybody has a link to one or could tell me how to find it, please PM me.

 

 

Might have been @BOB ELLISON that had a thread about attackometer a few years back

If they go by picking up spark, On a Kohler single the reading will be wrong. I don't care where you set it. A Kohler single sparks once per TWO REVOLUTIONS. 

[ebinmaine 67,610]

1 minute ago, squonk said:

If they go by picking up spark, On a Kohler single the reading will be wrong. I don't care where you set it. A Kohler single sparks once per TWO REVOLUTIONS. 

So something like the Kohler twin that I have here which Sparks every revolution would be able to use a tachometer like that....?

[Skipper 1,788]

Yes, that's why they are programmable. You tell it how many cylinders, and 2 or 4 stroke, and then it works. You may have to mess around with a bit though.

 

I can only say that the ones I have seen works fine. If that goes for all, I do not know.

 

There's a ton of them right here, and i assume just as many on ebay or amazon: https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20210518132535&SearchText=hour+meter+tacho

 

Edited May 18, 2021 by Skipper

[Tractorhead 9,064]

I edit my post above with more infos

 

even for @ebinmaine buddy bear

[squonk 41,155]

5 minutes ago, ebinmaine said:

So something like the Kohler twin that I have here which Sparks every revolution would be able to use a tachometer like that....?

If it fires every revolution yes. But all the ones I see do not have a setting for every other revolution. If you set it for single. it thinks you have an engine that fires every revolution.

 

I was in the phone directly with an engineer from ES trying to determine why the tach I bought would stop at 1500 RPM. When the light in my head went on remembering that the cam turns half speed and the points only open every other revolution, he said, "Oh that's why it doesn't work right. When it picks up a spark, it counts it as 1 revolution and there is nothing to tell it it's turning on the off cycle."