How to measure ATV and go-kart chain and sprockets

The problem it solves

Chain and sprockets are one of the few areas where an exact answer is available, because roller chain sizes are standardised — and yet people still order by guesswork because nobody tells them that pitch, roller width and tooth count are three separate numbers, all of which have to match.

Unlike almost everything else on these machines, chain is genuinely standardised. A 428 chain has the same pitch and roller dimensions whoever made it, because the numbering follows a published standard rather than a factory's preference. That makes this one of the few sheets here that can give you a definite answer.

What trips people up is that the chain number does not tell you everything you need. The chain has a length in links as well as a size, the sprockets have a tooth count each, and changing either tooth count changes the gearing — which is a decision rather than a replacement.

So measure the pitch to identify the chain, count the links to size it, count the teeth on both sprockets to preserve the gearing, and record all four before anything comes apart.

The mistakes this sheet exists to prevent

• Measuring pitch across one roller instead of from one pin centre to the next.
• Counting links on a worn chain and ordering that length. A stretched chain reads long.
• Replacing the chain and leaving worn sprockets, which chews the new chain in weeks.
• Changing a sprocket tooth count without meaning to change the gearing.
• Ordering by machine model rather than by measurement, on machines where the model tells you nothing.

How to use it

1. 01Check the calibration rule first — pitch is measured in fractions of an inch and small errors matter.
2. 02Measure from the centre of one pin to the centre of the next pin. That is the pitch.
3. 03Count teeth on both sprockets and write both down, even if you only intend to replace one.
4. 04Inspect the sprockets before ordering only a chain.