Workshop how-tos · 79Bike · Sur-Ron · Talaria
How to replace the chain and sprocket on an electric dirt bike
The final drive of an electric bike takes huge torque from a standstill. A stretched chain and shark-finned sprocket cost efficiency, add noise and eventually jump. Replacing them takes about an hour at home with a bit of method.
How to tell if the kit is worn
- Shark fins: sprocket teeth become asymmetrical and hooked.
- Chain lifts off the sprocket: pull a link at the back of the sprocket; if it lifts more than half a tooth, the chain is stretched.
- Out of adjustment: the adjusters are at the end of their range.
- Uneven tension: more than 10 mm difference in slack over one wheel turn.
Always replace the set
A new chain on a worn sprocket (or the reverse) wears out in a few rides: the two parts have bedded in together. Replace chain + rear sprocket (and the motor front sprocket if worn) at the same time. Keep the stock pitch and width (often 420 or 428 depending on the model) and tooth counts if you want to keep the original gearing.
Don't confuse it with the primary belt
On the 79Bike Falcon Pro and GT, the motor first drives a primary belt, then the chain drives the rear wheel. A slap on the motor side, or a frayed or slipping belt, is a belt issue, not a chain-kit issue. On Sur-Ron and Talaria, the primary drive varies by model and year: check before ordering.
Clip master link or riveted link?
A clip-type master link is handy for maintenance; fit the clip with its open end facing backwards (opposite to the chain's direction of travel). For very hard riding, a riveted link (with a chain tool) is safer. Either way, check the link every time you clean the chain.
Tools you need
- Chain breaker (or master-link pliers)
- Sockets and Allen keys
- Torque wrench
- Medium-strength thread locker
- Degreaser, brush, chain lube
Step-by-step procedure
- 1
Measure and order
Count the teeth on the rear and front sprockets, note the chain pitch (stamped on the side plates) and the number of links.
- 2
Remove the chain
Back the adjusters right off, open the master link or break a link, and remove the chain.
- 3
Remove the rear wheel
Loosen the axle and remove the wheel, minding the spacers and brake caliper (don't squeeze the lever).
- 4
Replace the sprocket
Undo the sprocket bolts in a cross pattern, clean the hub, fit the new sprocket and tighten the bolts with thread locker, in a cross pattern, to the manufacturer's torque.
- 5
Replace the front sprocket if needed
Remove the cover, then the motor output sprocket, and replace it if worn.
- 6
Refit wheel and chain
Refit the wheel with its spacers, fit the new chain (shortened to the right number of links if needed) and close the link.
- 7
Set tension
Set 20–35 mm of slack at the tightest spot and align the wheel (see the chain tension guide).
- 8
Re-check after 50 km
A new chain stretches quickly: re-check tension and sprocket bolt torque after the first ride.
Useful genuine parts
In stock, shipped in 3–10 business days.
FAQ
How long does a chain kit last?+
Depending on maintenance and terrain, from 1,500 to over 4,000 km. Mud and sand without cleaning cut its life dramatically; the right lube and correct tension extend it a lot.
Can I change the number of teeth on the sprocket?+
Technically yes, but it changes how the bike behaves and, on an L1e-B road-legal version, may affect compliance. Keep stock gearing for road use.
O-ring chain or standard?+
A sealed chain (O-ring / X-ring) lasts longer in muddy use. Keep the stock pitch and width and check clearance inside the guard.
Key takeaways
Always replace chain and sprocket together, keep the original pitch and gearing, use thread locker on the sprocket bolts and re-check tension after the first ride.
Need a hand?
Our workshop in Toulouse Sud (France) services 79Bike, Sur-Ron and Talaria. Send us a photo or video of the problem.
Related guides
These guides are for information only. If in doubt about a safety-critical part (brakes, steering, wheels), have a professional do the work. Always follow the manufacturer's manual.