Radio Shack (and others) has several inexpensive "Digital Multimeters" (DMMs) which can measure pulse frequencies. On sale they run about $50. That's a lot cheaper than a tach, and DMMs are always useful around the house, etc. They can measure pulse frequency from 400 on up (to 4 million hz), but the limit is the max pulse voltage, which is 10v, above which the circuitry is probably fried. Obviously, one would *never put the meter leads in series with the plug (10K volts ? would absolutely fry the meter), so what I did was make a loop of wire (actually 5 loops of 14ga multistrand) and then slipped the loop around the spark plug wire. so the spark plug wire goes from the ignition to the spark plug, clean like before. but wrapped around the sparkplug wire is now a loop of "pickup" wires. The DMM leads are connected to the loop. When idleing, the current in the spark plug wire "induces" a current in the pickup loop, which is hooked up to the DMM. It measured idle speed ok, but the frequency was very jumpy, so I need to stabilize the pulse pickups somehow. But, increase the throttle just a little, and the meter output jumps all over the place, as though it's internal circuitry can't "tag" or decide on a frequency. What does the pickup on a Stihl tach look like ? Maybe I could copy that. Any hardcore electronic hobbiests out there have any suggestions ... the money I save would mean a new pair of boots.