HIGH RPM's showing on Tach?

Discussion in 'Lawn Mowing' started by Doogiegh, Sep 5, 2002.

  1. Doogiegh

    Doogiegh LawnSite Senior Member
    Messages: 871

    Bought a tiny tach hour meter. Put it on my machine, Exmark Metro 32" 12.5 Kawi. The tach ran perfect and so did the hour meter part of it. The mower appeared to run 3600 RPM's exactly when at full throttle, and around 3450 when blades engaged.. Lowest I ever remember seeing was around 3300 in full deep grass.

    Screwed up and ripped the wire out of the tiny tach. Unrepairable.

    Bought a new one. Duh.

    Put it on machine.

    Now engine RPM's are showing around 3740 to 3800 at full throttle and seem to be around 3550 under full load, dipping down to 3460 under heavy grass...

    I even caught the tach at full throttle reporting 3800 and 3900 rpm numbers, not under load.

    Could my tach be off or is the throttle on the Exmark?

    Should I be concerned since even at 3800 RPM's, it's less than 10% above 3600 goal? Could my new tiny tach just simply be reading a little high?

    Does the placement of the wire on the spark plug wire itself have anything overall to do with the tiny tach reading and if I mess with the spark pickup wire, the tach will become "normal" again. (I installed the 2nd one wrong?)

    Anyone else's machine run at 3800 rpm's under no load, full throttle?

  2. As long as its registering should be ok- Maybe take to dealer or borrow another tach to double check your reading. If its off return it. Can't say on running yours fast- I do on mine

    high end rpms are governed, so thats where the adjustment will be if too fast
  3. awm

    awm LawnSite Gold Member
    Messages: 3,354

    id sure double check it cause one of your tachs,had to be giving false readings . too important to make a mistake on .
    my guess is your new ones off as i run 3850 and it dont leave any doubt that its all out at that speed. one factor ive noticed is with the rpm turned up high the drive belt can really be put under a strain.
    got another47.00 belt today. but im cutting thick grass rite now.
    and yea this command 20 has its greatest torque at top rpm. which was a surprise to me.

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