Chain and Sprockets

By |2017-01-10T08:35:35+00:00January 10th, 2017|Categories: KAJX.NET FILES|

AUSTRALIA, VICTORIA, KERANG. Chain and sprockets, the motion end of the motorcycle. A chain that is out of adjustment can cause many issues and dollars. A loose chain can be thrown off, and then lovingly impact the crankcase, that love is going to be an expensive repair. Also if the chain is too tight it can snap and the end result is the same, a love bite into the crankcase.

If you haven’t got an owners manual for your beast, get one, if you have one READ IT! Everything you need to know is in the manual (yep, harp over). As I have a Honda CRF250R the following is straight out of the manual. Service limits may vary, as well as tension settings may vary, however, the inspection part is the same for every chain driven motorcycle.

The service life of the chain depends on proper lubrication and adjustment. Poor maintenance can cause premature wear or damage to the drive chain or sprockets.

When the motorcycle is ridden on unusually dusty or muddy tracks, more frequent maintenance will be necessary.

Before servicing your drive chain, turn the engine OFF and check that your transmission is in neutral.


1. Turn the engine off, raise the rear wheel off the ground by placing an optional workstand or equivalent support under the engine and shift the transmission into neutral.

2. Check the drive chain slack (1) in the upper drive chain run midway between the drive sprocket (2) and driven sprocket (3). Drive chain slack should allow the following vertical movement by hand: 25 – 35 mm (1.0 – 1.4 in)

3. Check drive chain slack at several points along the chain. The slack should remain constant. If it isn’t, some links may be kinked and binding. Lubricating the chain will often eliminate binding and kinking.

NOTICE Excessive chain slack may allow the drive chain to damage the engine cases.

4. Inspect the drive chain for:

  • damaged rollers
  • loose pins
  • dry or rusted links
  • kinked or binding links
  • excessive wear

Replace the drive chain if it has damaged rollers, loose pins, or kinks that cannot be free. Lubricate the drive chain if it appears dry or shows signs of rust. Lubricate any kinked or binding links and work them free. Adjust chain slack if needed.


1. Check the chain slider (1) for wear. Replace it if below the service limit.


upper side: 5 mm (0.2 in)

lower side: 2.5 mm (0.10 in)

2. Check the chain guide slider (2) for wear. Replace the guide slider if it is worn to the bottom of the wear limit (3).


Check the upper drive chain roller (1) and lower drive chain roller (2) for wear or damage. Measure the diameter of the drive chain rollers and replace them if below the service limit.

Service Limit:

Upper roller: 33 mm (1.3 in)

Lower roller: 35 mm (1.4 in)

Replace the roller if necessary as follows. Install the upper drive chain roller (Green) with the “ ” mark (3) facing toward the bracket and lower drive chain roller (Black) with the large concave facing outside. Install the drive chain roller bolt and nut.

Clean the threads of the drive chain roller bolt and apply locking agent to the threads. Tighten the drive chain roller bolt and nut to the specified torque: 12 N°§m (1.2 kgf°§m, 9 lbf°§ft)


1. Loosen the rear axle nut (1).

2. Loosen the chain adjuster lock nuts (2) and turn the adjusting bolts (3) counterclockwise to decrease slack or clockwise to increase slack. Align the index marks (4) of the axle plates (5) with the same reference marks (6) on both sides of the swingarm.

3. Tighten the rear axle nut to the specified torque: 128 N°§m (13.1 kgf°§m, 94 lbf°§ft)

4. Recheck chain slack and adjust as necessary.

5. Turn the adjusting bolt counterclockwise until it touches the axle plates lightly. Then tighten the chain adjuster lock nuts to the specified torque while holding the adjusting bolts with a wrench. 27 N°§m (2.8 kgf°§m, 20 lbf°§ft)


Commercially prepared drive chain lubricants may be purchased at most motorcycle shops and should be used in preference to motor oil. Drive chain lubricant is recommended. If not available, use SAE 80 or 90 gear oil.

Saturate each chain joint so that the lubricant penetrates the space between adjacent surfaces of the link plates and rollers.


For maximum service life, the drive chain should be cleaned, lubricated, and adjusted before each outing.

1. Remove the master link retaining clip (1) with pliers. Do not bend or twist the clip.

2. Remove the master link (2). Remove the drive chain.

3. Clean the drive chain in high flash-point solvent and allow it to dry.

4. Inspect the drive chain for possible wear or damage. Replace the drive chain if it has damaged rollers, loose fitting links, or otherwise appears unserviceable.

Chain: Size/link: D.I.D 520DMA4/116RB | RK520TXZ/116RJ

5. Inspect the sprocket teeth for wear or damage. We recommend replacing the sprocket whenever a new chain is installed.

Both chain and sprockets must be in good condition, or the new replacement chain or sprocket(s) will wear rapidly.

Excessively worn sprocket teeth have a hooked, worn appearance. Replace any sprocket which is damaged or excessively worn.

NOTICE Use of a new chain with worn sprockets will cause rapid chain wear.

6. Install the chain.

7. Measure a section of the drive chain to determine whether the chain is worn beyond its service limit. Put the transmission in gear, and then turn the rear wheel forward until the lower section of the chain is pulled taut. With the chain held taut and any kinked joints straightened, measure the distance between a span of 17 pins, from pin centre to pin centre.

If the measurement exceeds the service limit, replace the chain. After the chain is measured, shift the transmission into neutral again before proceeding with inspection and service.

8. Lubricate the drive chain.

9. Pass the chain over the sprockets and join the ends of the chain with the master link. For ease of assembly, hold the chain ends against adjacent driven sprocket teeth while inserting the master link. Install the master link retaining clip so that the closed end of the clip will face the direction of forward wheel rotation.

10. Recheck chain slack and adjust as necessary.


• The master link is the most critical element of drive chain security. Master links are reusable, as long as they remain in excellent condition. We recommend installing a new master link retaining clip when the drive chain is reassembled.

• You may find it easier to install a new chain by connecting it to the old chain with a master link and pulling the old chain to position the new chain on the sprockets.


About the Author:

Kendall Jennings, KAJX Communications photojournalist since 2002. KAJX: Kendall A. Jennings (Photojournalist), who is a big The X-Files fan (what the X stands for in KAJX) and motorcycling fan. “I am extremely passionate about motorcycles and have been riding a motorcycle since I was 4 years old. I was introduced to the world of motocross racing in 1998 and haven’t looked back. Everyone should experience motorcycling whether it be a rider, passenger, racer, official or spectator. KAJX is all about sharing the motorcycling love. I am honest, opinioned and if I don't know something I will say so and then educate myself to provide an answer. Living is learning. I worked as a Motorcycle Spare Parts Manager for 15 years, I am also a qualified Outdoor Power Equipment Mechanic.” Kendall Jennings.
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