Replacing the Chain: Tools and Techniques

Parts and Part Quality:
Something we learned during this project is what we might call Tip #1: buy the best quality chain and sprocket you can afford.  There are a couple of reasons for this.  Since this job is so critical to the proper operation of the motorcycle, it doesn't make sense to try and save a few bucks on a cheap chain or sprockets.  And believe me, there are some really flimsy examples out there. 

Also, since this is a job that's only performed about once every 15,000 to 20,000 miles or so, and is a relatively difficult task, it pays in the long run to purchase the good stuff an avoid worries about having to do the job over again in 5,000 miles.  This isn't to say that expensive is always better, but name-brand, quality parts are usually the only way to go with projects like this.  Tip #2 is to think about sticking with OEM parts on this one. 

Gearing, Sprockets and Gear Ratios
One of the nice things about chain and sprocket drive on a motorcycle is that it's easy to mess with the ratios and find different levels of performance.  But another big lesson that we learned is that everything is a compromise, and changing a sprocket size can have implications that might not be readily apparent.  Gear ratios can be changed by using sprockets with different numbers of teeth, but it's important to be careful and to understand the implications. 

It's easy to get very deep into the physics of gear ratios, power curves and the like, and there have been many, many pixels devoted to explaining all of it on zillions of web sites and in many technical manuals and books. 

If you're interested, a good place to start learning about this stuff might be with checking out the webBikeWorld reviews of Gaetano Cocco's "Motorcycle Design and Technology: How and Why"; Kevin Cameron's excellent "Sportbike Performance Handbook" (one of my all-time favorites); or Professor Vitore Cossalter's "Motorcycle Dynamics".  These books don't necessarily cover gear ratios per se, but they provide some idea of the very, very complex physics that come into play when riding a motorcycle.

There are a many decent web articles out there also on chain and sprocket replacement, gear ratios and more.  Sport Rider has a concise and excellent article on the pros and cons of changing gear ratios, and "Mal's" free download of a motorcycle gearing calculator (Microsoft Excel spreadsheet) is a nice tool for playing "what if" with gear ratios whilst it calculates various engine speeds, miles per hour, kilometers per hour and more.

It's interesting to note that the gear ratios can be changed by either the front sprocket or the rear sprocket.  It's also possible to go ether way and end up with something better or worse than the original settings.  For example, this chart illustrates the various gear ratios that might be obtained by using different combinations of front (top row) and rear (left column) sprocket teeth:

This matrix uses a simple calculation: rear sprocket teeth/front sprocket teeth = gear ratio.  Our KTM 950 Adventure came with a 17-tooth front sprocket and a 42-tooth rear, for a 2.47:1 ratio (42/17 = 2.47), shown in red in the matrix above.  This means that the front sprocket turns 2.53 times to turn the rear wheel once.  Changing the ratio so that the front sprocket makes more turns for each single turn of the rear wheel can mean that the bike will be revving higher for any given speed, which was my goal. .

Other factors to consider are how the bike will be used (track or street), what type of roads the bike is being optimized for (slow commutes or long-distance, high-speed runs) and more.  The bottom line is this: when changing gear ratios, it's important to do some research and think carefully about the goals.  The old adage "if it ain't broke, don't fix it" should certainly be the watchword.  If the bike is currently running great, then why mess with success?  In the end, it may not be wise to try and second-guess the Matighoffen engineering staff and their collective wisdom and probably exhaustive testing.

We needed a Dremel tool with a grinding wheel to grind off one of the pins on a chain link to remove the endless chain that's installed at the factory (also see below).

A chain breaker is also required to remove the chain and a chain press is needed to install the master link on the new chain.  A chain riveting tool is also needed to "stake" the master link ends when the new chain is installed. 

The best tools are the combination chain breaker, side plate installer and riveter, like this Motion Pro kit, purchased through J.C Whitney for about $75.00 (although this tool broke during its first use, see below).

Disassembly:  

Next up was removing the endless chain that is used as original equipment.  We wanted to avoid having to remove the swingarm at all costs, and the only way to remove the endless chain is to grind off the end of one of the pins and push it out using the chain breaker tool.  This was an easy job with the Dremel; just be careful about wearing eye protection and keep the sparks and grit from flying all over the bike by using a piece of cardboard as a guide.

Once the pin end was ground off, it was easy to push it out of the chain link using the chain breaker.  We had some trouble with our chain breaker -- we couldn't get it off the chain because the design of the tool wouldn't allow the pin to fall out.  It ended up taking more time to get the chain breaker off of the loose chain than it did to get the chain off the bike.

By the way, chains are sold in links, e.g., "120 link chain", but the links are twice the number of side plates.  So when counting the plates as the pass by as the rear wheel is rotated, you'll find that the number of plates equals half the chain length.  A 120 link chain will have 60 side plates on one side of the chain.

We then used the Dremel tool to grind off the end of a pin, then used the chain breaker to pop out the pin.  The master link is then installed with all 4 extra O-rings (or in this case, X-rings).  Don't forget to grease up the new master link with the little package of special chain grease that's supplied with the chain.

Next, the side plate must be installed correctly on the master link.  A specialized motorcycle chain press works great for this job, but it can also be done with a Vice Grip or C-clamp.  (I watched a Dakar Rally mechanic use a vicegrip with a 10mm socket once during the race) Make sure the plate is installed correctly, that the O or X rings are installed, and that the plate is not cocked to one side or the other. 

Staking the pins on the master link is the most critical part of this whole project.  This must be done correctly to avoid having the chain come apart when riding.  A specialized motorcycle chain rivet tool must be used for this job.  Our Motion Pro kit had just the right attachments, but it's design is a bit clumsy, and we had to use what seemed like an enormous amount of pressure to get the pins to stake correctly; in fact, we broke the knurled handle on the tool (see photo). 

Road Racing World magazine ran an article with lots of photos in the August 2004 issue; they claim that the pins should be mushroomed over about 0.4mm larger in diameter then the master link pin.  We followed their instructions and we'll keep our fingers crossed that the chain will never come apart.  I've been checking it after every ride and so far everything seems fine.

The master link with the pin ends showing, prior to using the chain rivet tool to "stake" the ends.	Using the chain riveting tool to stake the ends of the master link.
The pins measured 0.208" diameter prior to staking; after staking, the mushroomed ends measured about 0.231".	The beautiful knurled handle of the Motion Pro chain press and rivet tool broke off with the amount of torque necessary to stake the ends of the master link pins.

After the chain is installed, we went through the normal procedure to adjust the chain.  We used the Vernier dial calipers to measure the distance from the swingarm to the adjuster bolt head and made sure it was even on both sides.  This helps get the rear wheel aligned correctly and seems to work well for this task.  We're in the process of experimenting with lasers to find an easy way to perform a motorcycle wheel alignment, and we'll check to see if the Vernier caliper method works.

Reprinted with permission of webBikeWorld.com