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Discussion Starter · #1 ·
I am wanted to adjust the RPM on idle and WOT on my Kohler Command Twin, What does everyone recommend? I have seen the photo tachs for sale on ebay. Do they work worth anything? If not those what else? Let me know, Would be nice if it also worked on a single cyl as my 112 is a single.

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There are a lot of digital tachometers/hour meters out there. This is one, as an example:

http://www.amazon.com/gp/product/B0049IFX56/ref=ox_sc_act_title_1?ie=UTF8&m=AR8XJJ19SNPNX

I have a similar digital unit. You wrap a wire around the spark plug wire, which lets it sense when the plug fires. They may or may not also have a ground wire. So installation is dead simple. It works on my twin-cylinder tractor, as well as my single-cylinder engines (4-stroke and 2-stroke). Mine has a 9999 RPM max. Others go higher (helpful for chainsaws and the like). Mine assumes that the plug fires on every revolution, whether or not that spark is actually used (many/most 4-stroke engines fire the plug on every revolution, even though only every other spark is actually used). Some other units let you configure it to for machines which really do only fire when required (higher-end 4-stroke engines, I presume).

The photo ones would probably work, if you exposed the flywheel, and put something shiny on it, for the eye to detect. But their use would be much more limited, and would need you to keep the tach pointed at the rotating shiny area. The inductive kind are not that much more expensive, and can be installed on the dash and monitored while using the tractor, if you want, plus they'll act as an hour meter. I move mine around to different machines as needed, for checking RPM's.
 

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Single or twin, these engines are all 1 spark/per revolution, so as long as you get a tach that is calibrated for 1 spark = 1 revolution, it will be accurate.
 

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Discussion Starter · #6 ·

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I have used the hour/tachometers on several of my equipment. It is nice on equipment that otherwise doesn't have an hour meter.
I used it on my GT5000s and put one on the generator also.

If I am just doing some adjustment on equipment and don't want to leave it on permanently I used this one.

Just beware that you have to do a little math. This one is set up for automotive where you would put the sensor on the main wire hence the setting for different cylinder engines. When I put it on the 4 cyl setting and use it on one cylinder it shows exactly 1/2 of what the actual RPM is.
(I think it is because you really should divide by 4 but then the wasted spark gives a x2 so the net results is x2)
Hope this makes sense - I am not an auto mechanic but that is the only thing I can get to make sense.
 
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