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Here is an inexpensive tachometer and hour meter for spark ignition engines. It is available on ebay from lots of sources with prices ranging from about US$14 to $60 including shipping. I paid about US$16 for mine from a US supplier. Just look for the photos. Using "tachometer hour" for searching, there were 35 offers on the first page of 50 items.
It has several limitations.
First off most descriptions say replaceable internal battery. I suppose that it is replaceable --if you have a spot welder for batteries and are willing to dig it out of the glue that vibration proofs it to the case. Also to get inside the case is a challenge as it has a pressed in rear cover with no pry notches. Don't consider the battery replaceable.
The RPM steps are in increments of 60 RPM when it is in one spark per revolution mode. This is OK with me as I am using it on a Hit and Miss engine where the RPM dances around some any way so this eliminates jitter in the last digits that you can't read any way.
The response time is slow. Takes a couple of seconds for each update.
Pros, besides being cheap.
Can be set for 2 sparks per revolution, 1 spark per revolution or 1 spark per every other revolution so it can be used with a wide variety of 2 and 4 stroke engines.
Very easy to use.
Besides the Tachometer mode there are two timers. One is a count down timer for service intervals which is useless for me. The other is a cumulative timer that runs when ever the engine is running for a total time on an engine. Both count in 0.1 hour intervals and can be reset.
There is a single 6 foot long wire coming from the unit that is wrapped around a spark plug wire. The wire was too long and too stiff for me so I replaced it with a #28 silicon test lead wire one foot long. I terminated this wire in a mini alligator clip that has as short, about 1/2 inch, length of 1/8 OD brass tubing soldered in the jaws. The brass tube was split so it can clamp around a spark plug wire.
After setting the sparks per revolution (stored in memory) operation is simple. Just clip the alligator clip around a spark plug wire. Everything else is automatic.
Gail in NM
It has several limitations.
First off most descriptions say replaceable internal battery. I suppose that it is replaceable --if you have a spot welder for batteries and are willing to dig it out of the glue that vibration proofs it to the case. Also to get inside the case is a challenge as it has a pressed in rear cover with no pry notches. Don't consider the battery replaceable.
The RPM steps are in increments of 60 RPM when it is in one spark per revolution mode. This is OK with me as I am using it on a Hit and Miss engine where the RPM dances around some any way so this eliminates jitter in the last digits that you can't read any way.
The response time is slow. Takes a couple of seconds for each update.
Pros, besides being cheap.
Can be set for 2 sparks per revolution, 1 spark per revolution or 1 spark per every other revolution so it can be used with a wide variety of 2 and 4 stroke engines.
Very easy to use.
Besides the Tachometer mode there are two timers. One is a count down timer for service intervals which is useless for me. The other is a cumulative timer that runs when ever the engine is running for a total time on an engine. Both count in 0.1 hour intervals and can be reset.
There is a single 6 foot long wire coming from the unit that is wrapped around a spark plug wire. The wire was too long and too stiff for me so I replaced it with a #28 silicon test lead wire one foot long. I terminated this wire in a mini alligator clip that has as short, about 1/2 inch, length of 1/8 OD brass tubing soldered in the jaws. The brass tube was split so it can clamp around a spark plug wire.
After setting the sparks per revolution (stored in memory) operation is simple. Just clip the alligator clip around a spark plug wire. Everything else is automatic.
Gail in NM
