Changing chain, sprockets and gearing

If you ride a small adventure bike hard on dirt, the chain and sprockets are the first things to wear out. The chain on this well-travelled Honda CRF300L Rally had stretched and the sprocket teeth were starting to hook, so it was booked in for a full chain-and-sprocket kit at a roadside workshop in Thailand — and a chance to shorten the gearing a touch for slow, technical off-road riding. Here is how the job went, step by step.

What you need

• A new chain — we fitted a D.I.D 520VX3 X-ring
• Matching front and rear sprockets (here a 13-tooth front and 45-tooth rear, down/up from 14/42)
• A chain breaker and riveting tool, plus an angle grinder or chain cutter
• Chain lube, sockets, a torque wrench, gloves and a paddock stand

Rolling in

With the bike up on its side stand and the rear wheel free to spin, the first job is simply to size up what you are dealing with.

The patient arrives — a well-travelled Honda CRF300L Rally is wheeled into a roadside workshop in Thailand.

Up on the stand and ready to work, with the rear wheel free to spin.

Sizing up the old kit

Spin the wheel and check the chain for tight spots and the sprockets for hooked, shark-fin teeth. Both were well past their best here.

The tired old chain alongside its replacement: a fresh D.I.D 520VX3 X-ring, still boxed.

Getting in behind the Honda Racing swingarm and bash plate to reach the chain.

A closer look at the worn drivetrain — a rusty, sun-baked chain (and a SwedishRider.com sticker that has seen some miles).

Splitting and removing the old chain

Grind the head off one chain rivet, punch the pin out, and the old chain lifts away in a single loop. Keep it to measure the new one against.

Splitting the old chain: an angle grinder takes the head off one rivet, throwing a few sparks.

Working the chain free around the rear sprocket and footpeg.

A punch and hammer drive the old pin out so the stretched chain can come off.

Old chain removed — the Mitas knobby and Honda Racing chain guide get a look-over too.

The culprit up close: the worn master link and pin from the old chain.

Out with the wheel, in with the new sprockets

Drop the rear wheel for clean access to both sprockets, then swap them. Clean the mating faces and torque the rear sprocket nuts evenly in a star pattern; at the front, the countershaft sprocket is where you set your gearing.

Dropping the rear wheel out of the swingarm for clear access to both sprockets.

Fitting the new front (countershaft) sprocket — this is where the gearing choice is made.

The rear wheel off the bike, ready for its sprocket swap, brake disc and all.

Knocking the old rear sprocket off its carrier — many hands make light work.

New rear sprocket bolted up, with sharp, square teeth replacing the worn ones.

The new sprocket although the shop did not do a good job cleaning around it.

The gearing change — about 15% more torque

Swapping sprockets was also the moment to change the bike’s character. The old setup ran a 14-tooth front and 42-tooth rear — a final-drive ratio of 42 ÷ 14 = 3.00. The new kit goes the other way on both ends: a 13-tooth front and a 45-tooth rear, or 45 ÷ 13 = 3.46.

Divide the two (3.46 ÷ 3.00 = 1.15) and you get about a 15% increase in torque. The trade is the same 15% off the top end: a lower top speed, but far stronger pull from low revs and much easier lugging up steep, loose climbs. For technical off-road riding, that is a swap well worth making.

Counting the old front sprocket: 14 teeth. The new one drops to 13.

The old rear sprocket counted out 42 teeth.

The maths on the bag: 42 / 14 = 3.00 becomes 45 / 13 = 3.46 — about 15% more torque.

Fitting and joining the new chain

Lay the new chain over both sprockets, cut it to the same length as the old one, then fit and rivet the master link. A proper X-ring chain must be riveted, not clipped, for this kind of riding.

Reassembly under way: new sprockets fitted, new chain ready to go on.

Refitting the rear wheel and laying the new chain over both sprockets.

Sizing the new chain — cut to match the length of the old one.

Pressing the master-link plate home with a chain tool.

Riveting the master link — a proper X-ring chain is riveted, never clipped.

Setting the slack and checking the tension

With everything torqued up, set the chain slack with the axle adjusters, keeping both adjuster marks even so the rear wheel stays in line.

Setting chain slack with the axle adjusters, both sides matched so the wheel runs true.

Then check the free-play. Find the midpoint of the lower run, push the chain up and then down, and judge the total travel between the two — on the CRF300L you want about a thumb’s width, roughly 25–35 mm. Too tight and the chain loads the gearbox output shaft and fights the suspension as it compresses; too loose and it can slap the swingarm or even jump the sprocket.

Checking free-play: Pull the chain out and on a new chain you should barely be able to pull it out any noticeable amount. On the worn old chain I could pull it out several mm and see the sprocket teeth as below.

Wheel back in, chain routed and the guard going back on.

Final adjustments and a spin of the wheel to check it all runs smooth and quiet.

Refitting the chain guard and skid plate to protect the new drivetrain off-road.

Lube it — and aim for the inside

One last job, and the one most people get wrong: lubricating the chain. The lube needs to land on the inside face of the chain — the side that wraps around the sprockets. As the wheel turns, sprocket contact and centrifugal force then carry it exactly where it is needed: into the rollers and the X-ring seals, and onto the tooth faces. Spray the inner run while slowly rolling the wheel, let it stand a few minutes so it creeps in, then wipe off the excess so it does not fling onto the tyre. Lube laid only on the outside looks shiny but never reaches the load-bearing surfaces — so aim inwards.

Finish with chain lube, aimed at the inside face of the chain where it wraps the sprocket.

Back on the road

Job done — fresh chain, new sprockets and shorter gearing, ready for the next adventure.

And that is it: a fresh D.I.D chain, new 13/45 sprockets and about 15% shorter gearing — ready for the next stretch of dirt.