The two measurements that identify any mini bike chain
You do not need a part number and you do not need to know what the bike shipped with. Two measurements off the chain in your hand are enough.
- Pitch — distance from the centre of one pin to the centre of the next. Measure across several links and divide, so a stretched chain does not throw the number off.
- Inner width — the gap between the inner side plates, which is the space the sprocket tooth sits in.
| Chain | Pitch (pin to pin) | Roller diameter | Inner width | Side plates |
|---|---|---|---|---|
| #35 | 3/8" — 0.375" | 0.200" | 3/16" — 0.1875" | Light |
| #41 | 1/2" — 0.500" | 0.306" | 1/4" — 0.250" | Thin |
| #420 | 1/2" — 0.500" | 0.306" | 1/4" — 0.250" | Thick — highest tensile |
So: a 3/8" pitch is unambiguous, that is #35. A 1/2" pitch narrows it to #41 or #420, and those two are dimensionally interchangeable — the difference is plate thickness and strength, not size. That is why a #420 chain drops onto a #41 sprocket without complaint, and why it is worth moving the whole drivetrain to #420 rather than mixing.
How many links do you need?
Link count is not a property of the chain — it is a property of your bike. It changes with sprocket size, wheelbase, and any chain tensioner you are running. Count the links on the chain you are replacing, then adjust:
| What changed | Effect on link count |
|---|---|
| Larger rear sprocket | More links — the chain has to wrap a bigger circle |
| Smaller clutch sprocket | Slightly fewer links |
| Stretched frame (extension tabs) | More links, roughly proportional to the extension |
| Added tensioner | Usually more links, since the tensioner takes up slack |
Our 420 chain, clutch & sprocket kit ships as a matched set at 120 links with a 10T clutch and 60T rear sprocket, in a 5/8" (16 mm) or 3/4" (19 mm) clutch bore, so the three parts already agree with each other. Chain that comes long is easy to shorten; chain that comes short is scrap.
Chain is one of three numbers
Pitch only tells you what meshes. Before ordering, confirm the crankshaft bore your clutch mounts on as well — the full sequence is in how clutch, chain and sprocket match up. If you are moving to a torque converter, note that the converter's driven sprocket also comes in #35 and #420, and it has to match whatever you decide here.
Starting from your machine instead
- Chain size on a Coleman CT200U / CT100U / BT200X
- Chain and sprocket alignment on a Predator 212 build
- Baja Warrior / Heat and Massimo MB200
Wrong-part traps
- Measuring one link. Chains stretch. Measure across ten pins and divide by ten.
- Assuming #41 and #420 are the same part. They interchange dimensionally, but the #41 becomes the weak link in a #420 drivetrain.
- Ordering by link count alone. Link count without pitch tells you nothing — a 120L #35 and a 120L #420 are different lengths.
- Reusing the old master link. The clip is the cheapest part in the system and the one that ends rides.
- Buying chain to fit a stretched frame without recounting. Extension tabs change wheelbase, and the chain has to grow with it.
FAQ
What size chain is on a mini bike?
Most gas mini bikes run either #35 (3/8" pitch) or #420 (1/2" pitch). Measure pin centre to pin centre to tell them apart — 0.375" is #35, 0.500" is #41 or #420.
What is a 420 chain equivalent to?
#420 shares its pitch (1/2"), roller diameter (0.306") and inner width (0.250") with #41. It is not equivalent in strength — #420 uses thicker side plates and carries a higher tensile rating, which is why it is the usual upgrade.
What is a 35 chain used for?
#35 is the lighter 3/8" pitch chain used on smaller mini bike and go kart drivetrains. It is narrower and lighter than #420 and pairs with #35 sprockets and clutch sprockets only.
How do I know how many links I need?
Count the links on the chain you are replacing, then add links if you have gone to a larger rear sprocket, stretched the frame, or added a tensioner. Buy long and shorten — a chain cut short cannot be recovered.
Can I mix a #35 chain with a #420 sprocket?
No. The pitch differs (3/8" vs 1/2"), so the chain cannot seat correctly on the teeth. Every sprocket in the drivetrain has to share one pitch.
Parts that fit
Shop chains, clutches & sprockets 420 chain, clutch & sprocket kit (10T / 60T / 120L)
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