Free printable · Maintenance and records
Spark plug record and reading log
The plug is the cheapest diagnostic instrument on the machine. A record of what it looked like each time turns it into a trend rather than a guess.
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3 pages. No account, no sign-up, no newsletter. Print it, copy it, hand it to somebody else.
Version v1.0 · September 2026. Opens in your browser's PDF viewer, where you can print directly.
The problem it solves
Everyone is told to read the plug and almost nobody writes down what they saw, so the reading is never compared against anything. One plug tells you very little. Four plugs over a year, with mileage against each, tell you whether something is drifting.
Who it is for
- Anyone chasing a running problem that comes and goes
- Owners who have changed jetting, an air filter or an exhaust and want to see the effect
- Anyone who wants to stop buying the wrong plug
What is on it
- What each field of a plug part number encodes
- A record block for the plug currently fitted
- A reading log with space for what the electrode looked like
- The observations worth recording, described rather than diagnosed
How to use it
- 01Read the plug after a run, not after idling in a garage.
- 02Record the part number in full, including letters that look like padding.
- 03Describe what you see rather than what you think it means. The interpretation can come later; the observation cannot be recovered.
Use it with the registry
Other sheets you may want
- GY6 maintenance schedule and service logA service record you build yourself from what your machine actually needs, rather than from a schedule invented for a machine nobody can identify.
- GY6 no spark diagnostic chartWorking back along the ignition circuit from the plug, one component at a time, without replacing anything on spec.
- Chinese scooter won't start: diagnostic chartA structured way through the four things an engine needs, ending at an observation you can make rather than a part you should buy.
Free to print, copy, and share — including in forums, clubs and workshops. If you find a mistake on one of these sheets, tell us and it gets corrected. Every sheet carries a version so you can tell which one you have. All printables.