Free printableIdentify your machineTSP-ID-11
Is my scooter a two-stroke or a four-stroke?
The question everything else depends on, settled from six things you can see without tools. Plus air-cooled or liquid-cooled while you are there.
Layout preview of page one. The PDF itself is typeset text, not an image.
Download — free, no email
2 pages. No account, no sign-up, no newsletter. Print it, copy it, hand it to somebody else.
TSP-ID-11 · version v1.0 · September 2026. Opens in your browser's PDF viewer, where you can print directly.
The problem it solves
Every other decision follows from this one. What oil it takes, whether smoke is a fault or normal, which engine codes apply, what a spark plug should look like, whether a rebuild means rings or valves. And a surprising number of owners genuinely do not know, because nobody told them and the badge does not say.
This is the most basic question in the library and it is not a stupid one. Small scooters were sold in both configurations, sometimes under the same badge in the same year, and once the machine is second-hand there is often nobody left to ask.
Getting it wrong is expensive in a quiet way. A two-stroke run without oil in its tank seizes. A four-stroke given premixed fuel runs badly and fouls plugs. Blue smoke on a two-stroke is the engine working; on a four-stroke it is wear. And half the diagnostic sheets in this library branch on the answer.
Six observations settle it, none of which needs a tool. While you are looking, the same trip answers whether it is air-cooled or liquid-cooled, which matters for the overheating and coolant sheets.
The mistakes this sheet exists to prevent
- Assuming a 50cc machine must be a two-stroke. Four-stroke 50s are extremely common.
- Assuming smoke means two-stroke. A worn four-stroke smokes too, for a different reason.
- Filling a two-stroke's separate oil tank with engine oil, or its fuel tank with premix on top of a working oil pump.
- Looking for a dipstick and concluding there is not one, when on many machines it is the oil filler cap itself.
- Deciding from the exhaust shape alone. It is a strong hint and not proof.
Who it is for
- Anyone who has just acquired a machine and does not know what it is
- Owners about to buy oil for the first time
- Anyone using the other sheets in this library, most of which branch on this answer
What is on it
- Six observations that settle it, none needing tools
- What each answer changes about how you look after the machine
- Air-cooled or liquid-cooled in the same trip
- A record block so nobody has to ask again
How to use it
- 01Work down the six observations. Three agreeing is conclusive.
- 02Check for a separate oil tank first — it is the single strongest indicator.
- 03Note the answer on the machine's own paperwork so the next owner is not guessing.
- 04If they contradict each other, believe the oil arrangement over the exhaust shape.
Use it with the registry
Other sheets you may want
- What the engine code on your crankcase meansEvery character in the code stamped on your crankcase, what it means, and why 139QMB and 1P39QMB are the same engine.
- What size engine do I actually have?The speedometer, the sticker and the title can all be wrong. The crankcase is not. How to settle displacement from physical evidence.
- Scooter smoking: what blue, white and black each meanThree colours, three quite different faults. And on a two-stroke, some smoke is meant to be there.
Free to print, copy, and share — including in forums, clubs and workshops. If you find a mistake on this sheet, tell us and it gets corrected. Quote TSP-ID-11 and the version so we know exactly which sheet you mean. All printables.