Replacing Sprockets and Chain on Ninja 650r

I spent this weekend replacing the engine and rear sprockets along with the chain. I’ve never done anything this complicated before and in the end I realized how uncomplicated it really was. So for those of you weary of doing the work yourself I thought I would step through the process I went through to give you an idea of what is involved.

Warning: I have limited mechanical knowledge. I’m just a guy trying to figure out how stuff works. Your service manual is your best guide when performing any major maintenance on your motorcycle.

If you don’t feel like reading through my sprocket saga you can watch a short video that discusses in general terms the process of changing the sprockets and chain.

These are the tasks that need to be completed, and order is key:

  1. Remove engine sprocket
  2. Remove rear wheel
  3. Remove rear sprocket
  4. Remove chain
  5. Install rear sprocket
  6. Install rear wheel
  7. Install chain
  8. Install engine sprocket

Removing the Engine Sprocket

Removing the engine sprocket was the most difficult step for me. Given that it was the first step and I was struggling so much, it didn’t help my moral very much either. You have to loosen the engine sprocket nut before you can take it off. Initially I thought to myself, “I’ll just put it in gear and crank it off.” I was actually turning over the engine by doing this so I decided to leave it in neutral in case the rotation of the sprocket while in gear causes any damage.
Then I thought, “I’ll just hold down the rear brake. That should stop it from spinning while I try to loosen the nut.” I faced backwards and sat on my gas tank. With one foot on the rear brake and balancing while trying to loosen the nut. The wheel kept turning! The rear brake wasn’t strong enough to prevent the sprocket from spinning.
So then I though, “I’ll just stick something in between the spokes and the swing arm to prevent the rear wheel from spinning completely. This stopped the rear wheel but as I attempted to unscrew the nut it wouldn’t give. So, I took a trip to Home Depot to buy a 18 inch breaker bar and a 3 foot piece of pipe (just in case). With the 3 foot breaker bar I STILL could not get the damn nut off. The sprocket was still spinning slightly because my chain was too “springy”. My chain was in such bad shape that I could not even rely on that to keep it still.
So then I took an old rag and tied it around the chain, the part that was being fed into the sprocket as I tried to loosen the nut. I gave the wrench a few turns and the rag jammed the sprocket and prevented it from moving. With very little pressure I felt that glorious *snap* and the engine sprocket nut was free! Woo hoo! Only took 2 hours!

So in short there are 3 methods you can try to prevent your engine sprocket rotating while loosening the nut on the output shaft:

1) Hold down the rear brake
2) Stick a pipe or piece of wood between the swing arm and rear wheel spokes
3) Tie a knot around the chain with a rag and feed it into the engine sprocket to jam it up

Oh, and after all this I realized that my mechanic didn’t give me a rubber mounted sprocket. Looks like they stuck me with a cheap-o one. I’ve developed a close relationship with my mechanic. He keeps my ride running and answers all my naive questions like “This page says to use ‘molybdenum disulfide grease’ but this page says to use ‘high temperature grease’…are those things…the same?” His savior status faded after I saw the cheap sprocket they used. All the more reason to maintain my motorcycle myself.

Removing the Rear Wheel

I was very nervous about removing the rear wheel. After all it’s a pretty important part…being one of the two wheels I rely on. I’ve been doing chain adjustments which require loosening the rear axle nut so that’s no big deal to me anymore. I even got myself a torque wrench (get one if you haven’t already). The idea of removing that rear axle was what worried me. I expected a thousand pieces to come falling down and me scrambling to remember where they all well. So with the rear wheel raise off the ground, and the axle nut removed I yanked out the axle and gently guided the wheel to the ground. “That was easy…*clunk*…WTH was that?!?” A coupling fell off, but I figured out where it had to go. No big deal. Take a deep breath.

Removing the Rear Sprocket

This is pretty simple after you’ve got the wheel off the bike. There are 6 bolts to remove. I needed to use the breaker bar to remove them. Something tells me that they were torqued on tighter than they should have been. They should be tightened to only 44 ft lbs.

Removing the Chain

I bought a Motion Pro Chain Breaker about a year ago thinking, “I can save money by replacing my own chain!” but for the past year I’ve been lazy and let my mechanic do it. I was determined to figure out how this collection of oddly shaped pieces fit together to break the mighty bond of the master link. First thing you do to remove the chain is to grind down the riveted ends so you can push the pin out. I don’t have a dremel, or a file, so I used a hack saw. After wielding the saw at an awkward angle I “grinded” the riveted end down in about 15 minutes. The size of the pin looked deceiving so I used a small pin from my chainbreaker tool to push the pin through. “Almost there, just one more push…*snap!*” The pin from my chain breaker broke. Then the next one did. Damn it! I had one pin left to use so I stopped and took another deep breath before I went breaking this one too. Ah ha! Maybe I should lube the chain to make it slide through more easily. *spray* *spray* *twist* *twist* Success!

Installing the Rear Sprocket

This was the easiest part of the whole process. Throw the new sprocket on and torque the bolts down with 44 ft lbs. I sped through this like a pro. Unfortunately this confidence doesn’t last very long.

Installing the Rear Wheel

The service manual told me to take off the rear brake caliper before removing the wheel. I was able to squeeze the wheel out without having to do so, but now I found that there was no way I was going to guide the wheel into that small space between the brake pads. I had to run to the store to get a metric hex wrench set first.

The wheel was kinda difficult to align between the swing arm. The couplings kept falling out and my frustration was peaking. Once again, a couple deep breaths and another attempt paved the way for success. I slid the axle back through the wheel and finger tightened the axle nut.

..OMG as I write this I just realized that I never replaced the cotter pin in the rear axle nut. *runs away to check* Ok well my rear axle nut was INCREDIBLY loose and was on the verge of coming off. Good thing I decided to blog about this…whew.

Anyways, I’ll need to adjust the chain later so finger tightening the axle nut is fine for now.

Installing the Chain

This was another part I was really worried about doing correctly. I never installed a master link before, so this was new territory again. I took out the master link out of its gooey bag. I made sure to place the gaskets in the appropriate places. The service manual said you could press the plate onto the pins of the master link with pliers but I didn’t have the strength. So I used my Motion Pro Chain tool to for the plate onto the master link pins. After the pins were poking out beyond the newly installed plate I used the Motion Pro tool to rivet the ends of the pins so the plate couldn’t come off. After I was done it looked exactly like it does when I get it back from the shop. Not too hard after all!

Installing the Engine Sprocket

So, just one thing left. Getting that engine sprocket, which caused me so much pain in the beginning, back on. In order to tighten the engine sprocket nut I stuck a rag in the area to jam it up, just like I did to loosen the nut. I bent the washer over the nut, reinstalled the sprocket sensor and I was done!

Conclusion
This was my first “major” maintenance task I’ve done on my motorcycle since I learned how to do an oil change, so I feel like this is a big step for me. More importantly, it’s given me the confidence to tinker with more stuff and learn more about motorcycle maintenance. My clutch has been slipping, so that’s the next thing on my list.

Anyone have any thoughts on the methods I discussed? Tips or suggestions?

  • Bucky

    Are you certain that the rear sprocket screws and front nut are not supposed to be secured by thread locking compound (Loctite, etc.)? The service manual has a code that tells you the torque and any special treatment such as thread locker or lubricant for each fastener on the bike.

    You are going to turn into a grease monkey after all. Forsake those computers, and go for it!

    (Bucky = grease monkey)

  • http://www.atlasrider.com Atlas

    The service manual actually tells you to “apply molybdenum disulfide oil to the threads of the output shaft and seating surface of the engine sprocket nut.” I read a thread on the KLR forum in which a guy (who seemed knowledgeable) confirmed this as well. So you have to do just the opposite. I don’t really understand why. The service manual has been explicit about everything else, so I assume it is correct.

    And yes I do feel like I’m turning into the grease monkey. In between the confusion and cursing I really enjoyed it :)

    Most importantly, I feel like I’ll be better prepared to fix something on my bike when it craps out in the middle of no where on one of my next trips.

  • rick

    Sorry I think I will pay to have it done! I would end up with a big mess and then I would end up having to pay some one anyway. Nice job!

  • http://www.honda-cb750.org/blog Honda Motorcycles Blog

    Here is how to do the same operation on a Honda CB750 Nighthawk. Chain and sprockets change.

  • Bucky

    See this link:

  • daniel o’b-b.

    it’s been a while since i checked your page, but i remember seeing this blog title, so i came back to it.
    i recently took my bike (bicycle [yea yea, whatever bill!]) apart to strip the paint and repaint it, then i became enamored with the idea that i might be able to take a lot of stuff apart. so, i started doing that.
    yesterday, i changed the chain, which was the first time i’d done it by myself.
    but, as i was lubing it up and working it in, i noticed that my free-wheel hub was grinding and making a lot of noise.
    now i’m like, “well, i changed the chain and disassembled most of the bike, time for a hub overhaul,” which, in all honesty, is nowhere near my capability level, but it’s your tenacity with your bike (motorcycle [yea whatever!]) that keeps me taking on “challenges.”

  • http://www.atlasrider.com Atlas

    Your capability level is mostly just perception. Most things are easier than they appear. At the very least just start googling and there is probably some walkthrough.

    Oh and I think I might be purchasing a bicycle myself (yea whatever!). I think it would be fun to take some of the nearby mountain roads down hill. …I think I can figure out a way to make a bicycle mount on my motorcycle.

  • keith

    what size/kind of socket did you use to remove the engine sprocket nut????

  • Theo_doh

    Very useful information. Thanks

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