Thruxton Sprockets

The chain on my Thruxton was about 6 years old and looking pretty ratty so I decided it was time for a new one. My buddy recently did some homework on chains and he ended up buying an EK X Ring chain so I followed suit. After hitting my Haynes manual to find out the right specs (525, 104 links) I picked one up. Found a good deal on an EK MVXZ 525 through ebay along with a chain tool to break the old one, and get the new one on.

Old Chain

My first mistake was trying to break the old chain off of my Thruxton with a $20 chain tool and not enough of the rivet ground down. So I broke the pin on that one and, surprise, it didn’t come with a spare. I took a pretty good chunk out of my knuckle when the pin broke and I was a bit pissed so I switched over to the cutting wheel and just cut the chain off. Should have just done that in the first place. Glad to have the old chain off too since it had a few links that weren’t flexing right. That’s why it felt funny while I was riding.

Since I was without a chain tool now I took the new one down to Destiny Motorsports and Garry cut it down for me. Great spot if you’re in Syracuse and you need an inspection or service. They’ve always done right by me and this time was no different.

Rear Sprocket

Now that I had the new chain at the right length I had to switch out the sprockets. I figured since I had the chain off it would make sense to upgrade the sprockets with some after market ones from British Customs. I picked up an aluminum rear sprocket and a fancy steel front too. I didn’t change the tooth ratio but I’m tempted to try a smaller front sprocket in the future.

Anyways getting the rear sprocket off was easy enough. Remove the rear wheel, pull the old one, put on the new one. The white stuff on the new sprocket is just lithium grease from the new chain. They come covered in that stuff and you’re gonna want to wipe as much of it off the chain before you ride on it.

Front Sprocket

Getting the front sprocket off was a bit of a trick. First off you’ve gotta bend back a huge washer that is bent down on the nut that holds the sprocket on. I did it with a screw driver but I’m sure there are better ways. This nut is huge by the way. 36 or 38mm and sockets that big get super pricey, not to mention a driver for it and a torque wrench if you want to torque it back down to spec.

After putting the new sprocket on you’ve gotta torque down the nut and flatten out the washer again. Flattening the washer down on the sprocket isn’t something you can do with a screwdriver. A small punch works perfectly if you’ve got one laying around.

New Chain

Pressing the master link on the new chain on is a real pain. I’ve already gone through one cheep chain tool so this time I got the real deal from EK. This tool is worth every penny and makes getting the master link on much easier than it would be normally. They’ve still got the EK chain tool on special at Moto-Chains so if you’re gonna buy one I’d recommend this one. It’ll press on the plates and press out pins. You can even use it for riveting.

So this is what the master link looks like after it’s been riveted. I didn’t take a picture of the chain when it was completely new. The photo below is the chain after 1200 miles through the white mountains. I was rushing to get the new chain on for the trip and forgot to snap a photo when it was fresh.

So that’s it. The new chain and sprockets are great. Not something you really notice when you’re riding but that’s the whole point. My old chain had a few links that weren’t flexing right and I could definitely feel the kinks when I was riding on it. This new one is super smooth which is the effect I was going for.

4 thoughts on “Thruxton Sprockets

  1. Forgot to mention that you might want to enlist the help of a friend when getting that front sprocket nut off ;). Glad to see your master link isn’t going to fall off.


    1. Good point. The nut on the front sprocket is on there tight and will take some serious twisting to loosen up. Always good to have an extra set of hands around to steady the bike, especially if you’ve got it rigged up on a set of bricks instead of on a proper stand like you should … or you could just put it back on the ground for this part >_<

      Thanks to Garrett for the help.


  2. Great post! I’m about to replace my chain/sprockets on my ’04 Thrux and I found your write up helpful. When I removed my front sprocket cover, I broke one of the bolts in the engine case. I presume the previous owner overtightened in the aluminum case, so your note about torque ratings is def warranted.

    It’s good to see another ’04 Thrux with an adventurous owner. Perhaps I’ll write up some of the work I have planned for the winter (valve clearances, polishing engine covers, and cleaning top-to-bottom).


    1. Hey sorry for the super late response. Hopefully you’ve got a watch on comments. Regardless I’d be interested to see whatever work you document.

      As for your broken bolt: did the bolt break or did it strip threads out of the case? I’ve found that the threads in the engine case are easily stripped. If you’re working with anything that supplies after market bolts for the engine cases (like your sprocket cover) be sure the bolts go deep enough into the engine case. If you try to torque them down and they’re not threaded into the engine case far enough you’ll pull the threads straight out.


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