How do I change the front sprocket?

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Tools Used

  • 3/8" ratchet
  • Torque wrenches: one for in-lbs range, one for ft-lbs range
  • 6" ratchet extension
  • 8mm socket
  • 24mm socket
  • 10mm wrench
  • 12mm wrench
  • 14mm wrench
  • 17mm wrench
  • Channel locks (2 Pair; optional)

Procedure

Begin by setting the bike up on the center stand. Next, remove the shift lever bolt (10mm) and pull the lever off the output shaft.

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Once the shift lever is out of the way, remove the sprocket cover bolts (8mm) and remove the sprocket cover. While the cover is off, go ahead and clean out all the gunk built-up inside the cover. This gunk may keep you from removing the cover easily in the first place. If it seems glued on, try tapping on it from the opposite side while someone pulls on it, and/or prying it off carefully with a screwdriver.

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Loosen the two (2) sprocket bolts (8mm) by either having someone hold the rear brake, or, (if you're limber enough) straddle the bike and loosen the bolts while holding the rear brake. Another way to break the bolts loose is to put the bike in 1st gear. When using this method, you will have to put the shift lever back on to the output shaft, put it in gear, then take the lever off again for easy access. To put it back in neutral, simply put the lever on again and shift.

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Now that you have access to the sprocket, you need to loosen up the chain. Start by loosening the rear torque link nut (17mm) next to the rear brake caliper.

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Once the torque link nut is loose, loosen both of the chain adjusting bolts (12mm) evenly. Start by loosening the lock nut at the base of the bolt (12mm) and then back the adjusting bolt out. Back these out about 10 turns to give enough slack. If you turn each one the same amount, you won't have to readjust the wheel alignment. Right side is shown below. Do both sides.

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Now that the adjusting bolts are loosened, loosen the axle nut. Remove the cotter pin by bending the outer pin straight and then pulling the cotter pin out with some channel locks. Once the cotter pin is removed, loosen the axle nut (24mm).

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You should be able to kick (or push) the tire forward to loosen the chain. You'll probably have to kick the tire all the way forward to get enough slack on the chain. Next, remove the factory sprocket. Remove the sprocket bolts (8mm) and slide the retaining plate to the side. If you have some difficulty removing the original sprocket by just pulling on it, slide the retaining plate out of the way and thread the bolts back in a couple of turns. Then you should be able to use two (2) channel locks to grip on to the bolts and pull the gear off. Try wiggling it as well. Make sure the retaining clip notches are lined up properly when pulling on the sprocket.

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Pull the old sprocket out of the chain and put the new one in (flat side OUT). Line up the new sprocket and press it on to the output shaft. Once the sprocket is on, bolt the retaining clip to the sprocket and torque the bolts down (87 in-lb or 9.8 N-m) while holding the rear brake or shifting again.

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So, the sprocket is on, but you still need to adjust the chain slack and rear wheel alignment. Go back to the rear wheel and tighten the chain adjusting bolts evenly. When you tighten the bolts the chain will slowly become tighter. Measure the chain slack to within 35-45mm. Check to make sure both axle nuts are on the same alignment notch. This should ensure the rear wheel alignment. Once the wheel is aligned and the chain has the proper slack, tighten the locknuts on the adjusting bolts. Torque the axle nut (80 ft-lb or 110 N-m) and torque link (24 ft-lb or 32 N-m) to the proper specifications. You may have to lower the right muffler in order to tighten the torque link properly. Don't forget to install a new cotter pin.

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Check your chain slack again and reinstall the sprocket cover. Push the shift lever back on the output shaft, making sure the alignment is correct. Use some blue Loctite to keep the bolt from falling off. Tighten the shift lever bolt and check the position of the lever by sitting on the bike and shifting it a few times.

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Step back and make sure you don't have any leftover bolts/parts. Take the bike for a spin and make sure everything is working okay. After riding, check the chain slack and adjust if necessary.