Bart Moto Co. Guide
CT70 Chain, Sprocket & Ratio Guide
Factory chain lengths, stock sprocket setups, and a quick ratio chart to help you pick the right gearing for stock CT70s, engine swaps, and extended swingarm builds.
CT70 Factory Chain & Sprocket Reference
Stock-style starting points for common CT70 models.
| Model | Front | Rear | Chain | Length |
|---|---|---|---|---|
| CT70 K0 1969–1970 | 15T | 38T | 420 | 88 links |
| CT70H K0 / HK1 4-speed | 14T | 45T | 420 | 92 links |
| CT70 K1–1982 | 15T | 35T | 420 | 86 links |
Notes
All CT70 models above use 420-pitch chain.
For every 1 inch of swingarm extension, add about 4 extra links.
Always fit and cut the chain to final length after installing the engine and swingarm.
For custom builds or extended swingarms, start with a longer chain, around 100 links, and size it during install.
For every 1 inch of swingarm extension, add about 4 extra links.
Always fit and cut the chain to final length after installing the engine and swingarm.
For custom builds or extended swingarms, start with a longer chain, around 100 links, and size it during install.
CT70 Sprocket Ratio Chart
Ratio is rear sprocket ÷ front sprocket. Lower numbers are taller. Higher numbers are shorter.
Highlight gearing for:
How to read: Ratio = Rear ÷ Front
Tall Higher top speed, less torque
Ideal Best all-around range
Short More torque, lower top speed
K0 Stock 15/38
HK0 / HK1 Stock 14/45
K1–82 Stock 15/35
← Shorter gearing
|
Taller gearing →
| Rear ↓ / Front → |
|---|