Re: Digital Hour Meter/tachometer

Posted by buckeye al on February 06, 2006 at 15:28:03 from (144.226.173.68):

In Reply to: Digital Hour Meter/tachometer posted by Tom R in TN on February 05, 2006 at 13:01:32:

Neighbor man has one on his lawn tractor. He asked me to install it for him and it works very well.

You have to get the right one though!

If you notice in the catalog, there are two different units and both are generally being marketed for single cylinder engines. One that is for battery ignition systems and one generally for mag fired engines. Reason is that most engines with battery ignition only spark in the compression stroke. No spark occurs between the intake and exhaust strokes so there is only one spark for every TWO revolutions of the crankshaft. Most mag fired single cylinder engines spark every revolution of the crank operating in what is termed the lost spark process. One spark does nothing and is simply lost between the engine's exhaust and intake strokes or cycles.

MOST of the John Deere 2 cylinder engines (not all but most) are lost spark engines with a spark to each plug on every revolution. This is true for MOST of both mag fired and battery ignition JD 2 cylinder tractors!

You did not say what model tractor you have but generally if your tractor is a letter series and is mag fired with anything but a Fairbanks DRV series mag, (not sure of the Splitdorf mags) then you would need the one that is for mag fired (lost spark) units. If your tractor is a numbered series FACTORY LP tractor or if it is a letter series that has the DRV series FB mag (maybe also the Splitdorf) then you need the distributor type type. The non LP numbered series tractors could be either type.

Soooo, if you install one of those tach hour meters, you need to get the right one even though either one will actually work becasue they're both just counting sparks to a spark plug. If however you get the wrong one for your machine, the reading will either be double the actual engine speed or half the engine speed! Also the operating hours will rack up at either double real time or at half real time!

Clear as mud right?

Posting what tractor and ingnition system you have would help.

Later.

Replies:

• Re: Digital Hour Meter/tachometer Glen in TX 21:12:15 02/06/06 (2)
  • Re: Digital Hour Meter/tachometer buckeye al 15:13:10 02/07/06 (1)
    • Re: Digital Hour Meter/tachometer Glen in TX 18:07:46 02/07/06 (0)

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