# Small Engine Tachometer recommendations?



## SayItAintSnow

As I read through many posts on this board, I notice that quite often that more experienced members than myself, stress the importance of our machines revving at the right top speed, in order to insure proper throwing distance. Makes perfect sense of course.

Recently, I thought I'd grab a small engine tach, figuring that it would be useful for my other power equipment as well.

I can see there's a lot choices out there, but like anything else, there's probably some devices that are better than others in terms of accuracy. Just as is the case with other diagnostic tools (compression gauges, spark indicators, etc.) I'm sure there are some tachs out there that are pure junk. Much like an unreliable compression gauge, getting a substantially wrong reading of engine speed, and making adjustments accordingly, in my opinion is worse than not having any reading, and leaving well enough alone....:grin:.

Any recommendations about small engine tachs? Best type? Wireless, optical, inductive coupled?
Any advice would be greatly appreciated. Thanks! :wink2:


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## vinnycom

i got an ebay tach/hour meter. it picks up the spark signal from the spark plug wire. induction.
it uses a lithium replaceble battery cr2450, works fine even in the cold. is it accurate? id say yes as it changes w/revs and at max throttle it reads at roughly 3600rpm, which is spec for a tecumseh 10hp flathead.

u can see it working in this vid of mine, its mounted temporarily and some electrical tape is covering the screen. i have since permanently mounted it to the control deck.


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## JLawrence08648

I'm reviewing old posts on this right now. I did a search for "tach".

The Vibratach has been around for 40 years but I don't know the accuracy of it.

The point and shoot tachs require a mark on something spinning, flywheel, crankshaft, or crank pulley to measure the true engine rpms. Similar to a timing light used on cars. I believe the mark can be tape, paint, chalk, magic marker.


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## EdwardC

I've only used cheap optical handheld type units, I use it for a lot of different RPM measurement needs with no problem. I don't know about the accuracy, but it's good enough for me.


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## classiccat

I keep a hardline tach/hourmeter mounted permanently on my keeper machines.


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## Motor City

I have a Sandec, pretty happy with it so far.


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## ourkid2000

vinnycom said:


> i got an ebay tach/hour meter. it picks up the spark signal from the spark plug wire. induction.
> it uses a lithium replaceble battery cr2450, works fine even in the cold. is it accurate? id say yes as it changes w/revs and at max throttle it reads at roughly 3600rpm, which is spec for a tecumseh 10hp flathead.
> 
> u can see it working in this vid of mine, its mounted temporarily and some electrical tape is covering the screen. i have since permanently mounted it to the control deck.
> 
> 
> https://www.youtube.com/watch?v=xb52J9uapl8&t


Vinnycom, I use the same tach. You sure you can replace that battery? Mine looks completely sealed. Works well otherwise


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## RedOctobyr

I have several of the inductive type of tachometers/hour meters. Most of mine are the inexpensive ~$10 eBay ones. None of mine allow replacing the batteries that I know of, however. That would be a nice feature. 

vinnycom, do you have a link to the one you bought? 

I've bought 2 of these, for the machines where I wanted a slightly better unit. Hardline Products HR-8061-2. It works for 1- or 2-cylinder engines, up to 16,000 RPM. That may sound useless, but it allows checking chainsaw RPMs as well (some saws have suggested tuning the carb based on RPM with no load, typically >10,000 RPM): 

https://www.amazon.com/gp/product/B000FOOAXY/ref=oh_aui_search_detailpage?ie=UTF8

I haven't seen signs of RPM inaccuracy in the ones that have allowed checking that (when used with my generators, where I can compare against the frequency shown on my Kill-A-Watt, for instance). 

The optical type sound handy (nothing installed on the machine), but you need a clear view of something like the flywheel to use them. The inductive are very easy to install (just wrap the wire around the spark plug wire), and also permit monitoring RPM during use, as well as giving you an hour meter. The hour meter can be nice to get a sense of how much time you have on your oil, etc.


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## vinnycom

ourkid2000 said:


> Vinnycom, I use the same tach. You sure you can replace that battery? Mine looks completely sealed. Works well otherwise


mine is replaceble, but there are ones that are not, it usually states so in the listing info. i bought a cr2450 only too find one already installed, but was missing the rubber gasket on the battery cover, so i just used gorilla black duct tape to cover up the battery cover area


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## RIT333

With some prying, the bottom panel can be opened up, and the battery can then be replaced - even on the non-replaceable ones. I was successful with mine.


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## jsup

I've been looking for an hour meter, but can't find one without a tach. Which is OK I guess. Is there any other method of doing this other than using the spark plug wire for the tach? 

How does this little wire stay on the plug wire? Can it be done neatly? How long is this wire?


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## vinnycom

this the one i got, description says replaceable battery cr2450
wrap the wire about 5 times tightly around spark plug wire, i used electrical tape to keep it on sp wire

https://www.ebay.ca/itm/371995370550?ul_noapp=true


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## drmerdp

Like a few others mentioned, I use hardline tach/hour meters on my machines. Currently 4 machines with the hardline.

But my go to chainsaw/ Any gas engine diagnostic tach is the tinytach 20k. Little bulky but very accurate and a super fast refresh speed.

https://tinytach.com/handheld-tachometers



jsup said:


> I've been looking for an hour meter, but can't find one without a tach. Which is OK I guess. Is there any other method of doing this other than using the spark plug wire for the tach?
> 
> How does this little wire stay on the plug wire? Can it be done neatly? How long is this wire?


I Have a particular way of wrapping and knotting, but a zip tie is quick and simple.


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## vinnycom

drmerdp said:


> Like a few others mentioned, I use hardline tach/hour meters on my machines. Currently 4 machines with the hardline.
> 
> But my go to chainsaw/ Any gas engine diagnostic tach is the tinytach 20k. Little bulky but very accurate and a super fast refresh speed.
> 
> https://tinytach.com/handheld-tachometers
> 
> .


pricey little thing @$85, cost more than i paid for my used sb lol, i think i'll stick w/my $10 tach


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## SayItAintSnow

*Thanks for all of the responses...*.:wink2:

I have been tempted to pick up a few of the inductively coupled electronic tachs that work off of spark plug pulses, but haven't, because I really haven't been able to find something definitive with regards to how accurate these devices really are.

As I'm sure many of you know, there's a lot of cheap, unreliable China made electronic and mechanical devices for measuring everything from temperature, to air pressure, to cylinder compression, and many other criteria. Many times, you can buy four or five of these cheap devices to take a single fixed measurement, only to discover that you'll get four or five vastly different results. (Ask me how I know this.....lol). So you're left asking: which one is correct? It would be fair for you to ask: Are _*any*_ of them correct?

For example, cheap compression gauges are notorious for this, as are air pressure gauges. (I had an A/P gauge on my compressor that I used for tire inflation, and found that the air pressure reading was off by about 15 psi for an average car tire!).

Knowing a little about how these inductively coupled devices work electronically, it's not hard to imagine ways in which these devices might over or under register actual rpm because of lack of quality control-- meaning that you would not want to make a critical engine speed adjustment unless you had some way to verify accuracy. Some of the same reservations I have for these, would also apply to the ones that work on the strobe principle, using reflective tape on the flywheel, crank pulley, etc.

Now remarkably, I have found very good references on the reliability of the type that "JLawrence" brought up, even though when I first saw one of these, I confess I thought it was a bit of a Rube Goldberg device. Turns out though, these German made sirometers made by Treysit and marketed in the U.S. by Briggs, if used correctly, supposedly give you a very accurate reading of RPM's, using the principles of resonance and harmonic motion. Apparently, these will also work on an electric motor, which would provide a good way to test. For example, if you have a motor that is spec'd for a fixed 3200 rpm, the sirometer should give you a reading that's pretty darn close to 3200 if it's an accurate device.

I suppose another alternative would be to use a variable strobe, with a dial-able range of pulse frequencies. Rotate the dial until the pulley or flywheel appear to stand still, then look at the frequency indicated on the strobe. Haven't even looked at those. Probably pretty pricey....

I'd love to just spend $10 or 20 bucks on one of those inductive devices and be done with it, but without any sense of how accurate they really are, it would never be something I would rely on for making adjustments, so I wouldn't see much point. Unfortunately, in the past, I have spent more than enough money on inexpensive devices that have led me astray....lol.:facepalm_zpsdj194qh


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## vinnycom

if u want to check accuracy of a tach, test it out on a car or motorcycle that has plug wires and a tach. wrap the wire around any plug wire and compare with tach in car/motorcycle


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## 1132le

just got my new laser tach last night
amazon 11.99 works perfect
came in 2 days
old tach was sold with the 1332 blower mounted in the cab


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## SayItAintSnow

Ha.....that makes perfect sense Vinny......why the heck didn't I think of that ?!...lol

My vintage Firebird Formula has a tach in it. I'll order one from Amazon, and if it turns out not to be accurate, I can always send it back with no problem. Good idea. 

Still kind of intrigued by that Briggs spirometer though. But even if those are accurate, it will be like the difference in reading your answer on an old slide rule vs. a digital calculator. That would be close enough though. Heck, slide rules got us to the moon and back!


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## RedOctobyr

SayItAintSnow said:


> I have been tempted to pick up a few of the inductively coupled electronic tachs that work off of spark plug pulses, but haven't, because I really haven't been able to find something definitive with regards to how accurate these devices really are.


I have one of $10 eBay ones on my Honda EU2000i. That is supposed to idle at 3000 RPM, or 4300 RPM, depending on the selected operation mode. It uses an electronically-controlled throttle, so I have to think that the generator's electronics monitor the engine's RPM, and adjust the throttle accordingly to get the desired RPM. It's not just a typical mechanical governor with a spring. 

I just checked, my cheap inductive tach/hourmeter shows 3000, and 4260. One value is dead-on, the other displays within 40 RPM of what it should be (and the engine may not actually be at 4300). That's "good enough" in my book. It's not off by 300 or something. My Ariens manual calls for 3600 +/- 150, so even being off by 40 would be within the tolerance on the RPM setting, as an example. 



> I suppose another alternative would be to use a variable strobe, with a dial-able range of pulse frequencies. Rotate the dial until the pulley or flywheel appear to stand still, then look at the frequency indicated on the strobe. Haven't even looked at those. Probably pretty pricey....


This device still has its own variability, and isn't guaranteed to be perfect. It's just different. 



> I'd love to just spend $10 or 20 bucks on one of those inductive devices and be done with it, but without any sense of how accurate they really are, it would never be something I would rely on for making adjustments, so I wouldn't see much point. Unfortunately, in the past, I have spent more than enough money on inexpensive devices that have led me astray....lol.:facepalm_zpsdj194qh


I realize my info is just a single example, but maybe it's of some use. If you want to go with something other than the absolute-cheapest option, you could do the ~$20 Hardline. 

I considered a sirometer before buying my first inductive unit. But decided I'd only be able to use it for "spot checks", vs easily keeping an eye on my tractor's RPM during the season, the snowblower's, etc. And it doesn't provide an hour meter function. I've been happy with my inductive units. 

And it can be interesting watching the RPM as I drive the blower into deeper snow, to see how much the engine speed sags under the load. That helped clue me in to a weak governor spring on my blower, which was letting the RPM by more than it should. 



vinnycom said:


> if u want to check accuracy of a tach, test it out on a car or motorcycle that has plug wires and a tach. wrap the wire around any plug wire and compare with tach in car/motorcycle


I think that's a great idea, and an easy way to double-check. Of course, then you have the question of how accurately you can read the vehicle's tachometer. And if your car idles at 1000 RPM, maybe with ignition pulses every other revolution (thus displaying as 500), does that tell you how acccurate it is right around 3600. But it could certainly help show if they are both pretty close, without making you buy anything additional.


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## vinnycom

for these motors, close is good enough, specs say the tach is +/- 10rpm


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## jsup

Any reason why a tach can't be done like on a car? To the negative side of the ignition coil? How do the wires attach to the ignition coil?


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## SayItAintSnow

vinnycom said:


> for these motors, close is good enough, specs say the tach is +/- 10rpm


Oh I completely agree Vinny.....10 rpm +/- would be plenty close.
The thing is, it's not hard to imagine some of these cheapo no-name units being off by a whole lot more. And without having any way to verify it's working correctly, you sure wouldn't want to trust it for any adjustments.

But getting back to your idea of using the onboard tach in my car......_that spawned another idea!_

I have OBD software on one of my laptops that I could hook up to my car. One of the parameters it supplies in real-time is engine rpms. That figure is coming from the vehicle's PCM and should be VERY accurate.
Having the laptop on the fender, and the inductive tach attached to the plug on cyl. #1, I would be able to see the readings side by side. Not only that, but I could manually rotate the throttle and try the test at different speeds.

The "Hardline" tach that Redoctobyr suggested has some pretty decent reviews--- that is if I'm looking at the right one. It's only 24 bucks on Amazon which is certainly cheap enough. I may start with that one and apply the test described above. (Now all I need is a sunny day in the 40's):grin:

Thanks guys!


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## vinnycom

i doubt its +/- 10rpms, it has a delay of reading actual rpms, but if its +/-50revs i can live w/that. guys on utube already verified the induction tachs, but easy to confirm on a per tach basis when buying it using a car tach.


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## RedOctobyr

Beautiful, great idea with the OBD port! I didn't even think of that. I have an Android code reader that connects to the port, and will show RPM, that's a slick way to check the reading, while getting a more accurate value than the needle can display. 

And like I posted, even my cheap eBay one was within 0-40 RPM, with the best reference that I had handy.


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## SayItAintSnow

Red'

Yeah....I think using my old Firebird Formula will provide as accurate a reference as I'm likely to get. During that era, the cars with V8's used a distributor called an "Opti-spark" which originated with the Corvettes. It utilized a metal disk with two concentric circles of slots cut into it, to act as a strobe in conjunction with a couple of laser diodes. Not only did the opti-spark provide the PCM with a highly accurate engine RPM reading, but it literally would feed back every change in rotation of the crank down to an accuracy of 1 degree.

As I think about it, the hardest part of this will be coiling the tach's sensor wire around the plug wire. The LT1 engines in these F-body cars of that era were notoriously hard to work on, including simple tasks like changing plugs. Dealerships would charge $600-$700 to change a set of plugs. I've done all the maintenance myself on this car for 23 years, and getting at the plugs involves climbing into the engine compartment, balancing over the top of the engine, while reaching down into the very limited space to access a few of them. Others can be reached from underneath the engine. I'm 65 now, so I'm clearly not looking forward to the next tune up.....:smiley-whacky017:

BTW, is this the tach you were referring to?
https://www.amazon.com/Hardline-Products-HR-8061-2-Tachometer-2-Cylinder/dp/B000FOOAXY/ref=sr_1_2?ie=UTF8&qid=1516367551&sr=8-2&keywords=hardline+tachometer

I notice in that Amazon lists it as being for 2-cyl, but reviewers report it has adjustable modes for 1 cyl. or more.

_*Thanks!*_


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## SayItAintSnow

jsup said:


> Any reason why a tach can't be done like on a car? To the negative side of the ignition coil? How do the wires attach to the ignition coil?


Jsup,

That's a good question. Add on tachs like that are not very expensive either. Whadya' bet someone here has done it! :grin:

The only question I would have about it, insofar as a permanent installation, is that most of those dash mount tachs weren't designed to be out in the weather.


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## RedOctobyr

Yes, that's the Hardline model I bought, as linked in my earlier post. It's capable of 2 cylinders, but works fine with just 1, as well. You can select the numbers of cylinders on the engine.


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## jsup

SayItAintSnow said:


> Jsup,
> 
> That's a good question. Add on tachs like that are not very expensive either. Whadya' bet someone here has done it! :grin:
> 
> The only question I would have about it, insofar as a permanent installation, is that most of those dash mount tachs weren't designed to be out in the weather.


Marine gauges and a gauge pod. Do a 2 inch gauge pod on the "dash" They're small.

https://www.glowshiftdirect.com/uni...m=1100502001640&utm_content=All Products_Bing

I'm thinking tach and hour meter.


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## RedOctobyr

I'll confess I'm kinda struggling to understand the benefit of going that route, vs putting on a small $10 (if you want to go inexpensive) device that can serve both functions  

But it's not my machine. Obviously, go with whatever appeals to you!


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## KennyW in CT

I swear by my DTI TT-20K


Hand Held TT-20K Small Engine Tachometer


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## KOBO

jsup said:


> I'm thinking tach and hour meter.



https://www.ebay.com/itm/Motorcycle...d=162465682235&_trksid=p2047675.c100752.m1982

:wink2:


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## vinnycom

I Permanently Installed The Tach To The Control Deck


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## jsup

KOBO said:


> https://www.ebay.com/itm/Motorcycle...d=162465682235&_trksid=p2047675.c100752.m1982
> 
> :wink2:


That's perfect, a motorcycle one is made to be out in the winter. 

I looked, that's 13K limit. I'm looking for a 4-6K limit, it's a more accurate scale, when the engine tops out at 3.6K. 

There are analog tachs with hour meters on them, but they're 3.375 inches in diameter, I think that may be a little big. It could be done in a single gauge pod, instead of two 2 1/16 inch smaller ones. 

If anyone cares, I am finding that the old style "switches" for 4/6/8 cylinders are being replaced with "programmable". A single cyl is a .5 cycle setting.

Something like this, but smaller, would be perfect. Hour meter, and tach. Just 3.375 which is what keeps me from jumping on it.

https://www.silverdalemarine.com/st...s_Johnson_Evinrude_and_Bombardier_Gauges.html


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## crazzywolfie

jsup said:


> Any reason why a tach can't be done like on a car? To the negative side of the ignition coil? How do the wires attach to the ignition coil?


i am guessing the big reason people don't run them is the 12vdc power required to run the gauges and snowblowers not having that. it doesn't mean it can't be done. just takes a bit more to do.


vinnycom said:


> i doubt its +/- 10rpms, it has a delay of reading actual rpms, but if its +/-50revs i can live w/that. guys on utube already verified the induction tachs, but easy to confirm on a per tach basis when buying it using a car tach.


ya i got one of those too. it seems pretty actuate but it did have me a bit worried when i was using it on a 5hp tecumseh and it was running 3600rpm and i was reading they are suppose to be running about 3400 with a max rpm of about 3500. i know the engine was a bit loose since it was locked up when i got it but it was a bit worrysome to see the engine rpm that high. i haven't tried the tach on an engine i am more likely to get a reading i trust yet.


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## aldfam4

Question, I have a 30 year old Sears/Craftsman Engine Analyzer I used on my older cars before electronic ignitions arrived. Could I use the tachometer clip on the engine analyzer and put it on a snow blower spark plug wire to get a rpm reading? If so, couldn't that reading be used to compare accuracy of these digital lcd engine tachs Vinny was alluding to?


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## 1132le

just bought this checked my other snowblower i set rpm wîth another tach it was the same

https://www.amazon.com/gp/product/B00EUY6FNI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
11.99


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## jsup

aldfam4 said:


> Question, I have a 30 year old Sears/Craftsman Engine Analyzer I used on my older cars before electronic ignitions arrived. Could I use the tachometer clip on the engine analyzer and put it on a snow blower spark plug wire to get a rpm reading? If so, couldn't that reading be used to compare accuracy of these digital lcd engine tachs Vinny was alluding to?


I guess it depends if it has a 1 cyl setting or not. If you set it for 4,6,8 it won't register right.


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## jonnied12

jsup said:


> I guess it depends if it has a 1 cyl setting or not. If you set it for 4,6,8 it won't register right.


 Math? xxx RPM x 4,6,8:behindsofa:


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## SayItAintSnow

vinnycom said:


> I Permanently Installed The Tach To The Control Deck
> 
> https://www.youtube.com/watch?v=mIZIfEEdzqI


Vinny,

Thanks for this brand new video, and for posting it here in this thread!
Looks good. :wink2:
Again, thanks to everyone here for their input on this subject. Some very good ideas regarding the proving of tachometer accuracy. It's a shame we have to go through this exercise, but like most cheap products out there today, you can't be sure anymore that when you buy something, that it is actually going to do what it is supposed to do. I have a few compression gauges, and tire pressure gauges that are complete junk for example. Bad measurements can result in costly damage or unnecessary repairs.

What was that old Russian expression that Reagan used on Gorbachev? 
"Доверяй, но проверяй" {Doveryai, no proveryai} -----"Trust....but verify". :icon_smile_big:

.


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## jsup

jonnied12 said:


> Math? xxx RPM x 4,6,8:behindsofa:


That's what the switches do on the back of the tack. 

You'd have to use the 4 and multiply it by 4? IDK. If set on 4, does it read twice as much as it does on 8? IDK, never tried it.


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## drmerdp

The switches are for cars with a single ignition coil. The coil ground is the tach trigger, the switches scale to represent the right rpm based on Input pulses. 4 pulses per revolution (v8) 3 pulses per revolution (v6) 2 pulses per revolution (I4)

The inductive tach on a single cylinder engine is identifying the one pulse every two revolutions. Put that same tach on a twin cylinder engine that has individual ignition coils for each cylinder and fires alternately, still shows the right RPM. 

The same inductive coil on a single ignition coil twin cylinder engine, the rpms will show double the actual speed, unless there is a setting for this configuration.


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## MrPlod

vinnycom said:


> I Permanently Installed The Tach To The Control Deck
> 
> https://www.youtube.com/watch?v=mIZIfEEdzqI


Nice. I might try that once I get the axle bearings replaced.


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## Spectrum

I've been happy with this unit. Works fine in proximity with out the pick-up wire. I have seen none of the instability mentioned in some reviews. Either the users were the problem or the product has been refined.

I had a Tiny Tach with the wrap around lead for years but decide to upgrade when the battery wound down.


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## Grunt

Spectrum said:


> I've been happy with this unit. Works fine in proximity with out the pick-up wire. I have seen none of the instability mentioned in some reviews. Either the users were the problem or the product has been refined.I had a Tiny Tach with the wrap around lead for years but decide to upgrade when the battery wound down.


I agree with Pete, I have the same tach and have confidence in it's accuracy and fast refresh rate.


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