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Old 04-13-2010, 12:10 PM   #1
FatChance OP
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Joined: Jun 2003
Location: Durango, Colorado, USA
Oddometer: 10,598
How to change and adapt gearing on a dual sport (DR650)

Now that winter is (finally) past, I'm jumping into spring bike maintenance and upgrades, even though it was snowing this morning when I did this. One of the jobs I have been planning on my 2005 DR650 is to upgrade the gearing. These directions will also work for other dual sports with some possible bike-related changes. This may be simple stuff for most, but this should be a tutorial for those who haven't done it before.

The U.S. DR650 comes with 15/42 (front/rear sprocket sizes) gearing. That gives a 0.357 ratio which is fine for cruising on the highway, but most people want a numerically lower ratio to multiply the torque a little more at the expense of top speed. A dual sport has to work off-road and also get you to and from the trails without riding at red line, so picking the right gearing is a juggling act and a compromise. You can get better gearing with either a smaller front sprocket or a larger rear sprocket (or both). Most people seem to just put on a 14 tooth front sprocket to get 14/42 (0.333) on their DR650, a 6.7% change from stock and are they happy enough with that.

Where I live in the mountains, I want even lower numerical gearing for crawling up mountain trails and because we are 180 miles from the nearest freeway, maximum speed isn't an issue. Until now, I have been running 14/45 gearing (0.311), or 12.8% lower than stock. The bike crawls and accelerates much better and will still cruise 65-70 on the highway. I wanted three things. 1) to have an even lower gear ratio for offroad, 2) to have more top speed for riding pavement over to Moab or up to Wyoming and 3) be able to switch gear ratios easily from low to high gearing without breaking the chain or removing the rear wheel so I don't have to compromise. But, I don't want to drop to a 13/45 because I think a 14T front is as small as you can go in front and still be good to your chain. Also, I cannot fit 15/45 for the road because the stock 110 link chain is too short for that combination.

I decided to get a new 48T rear sprocket and use 14/15/16T front sprockets that are clipped in for easy switching. This gives the best of all worlds for me. To fit this, I also ordered a new 120 link O-ring 525 Bikemaster chain from Motorcycle Superstore and the 48T steel rear and a 16T front sprocket from Jesse (look HERE). I already had sitting around an unused 14T and the stock 15T I took off when the bike was new. I also ordered a couple circlips from Jesse as an alternative “quick change” method of holding on the front sprocket so I could easily change from 14/48 to 15/48 to 16/48 wherever I was in about 10 minutes.

Here are the applicable gear ratios:

14/42 – 0.333 (most popular)
15/42 – 0.357 (stock)
16/42 – 0.381 (for droning on the interstate)

14/45 – 0.311 (the best all-around, IMHO)
15/45 – 0.333 (same as the most popular)
16/45 – 0.355 (about the same as stock)

14/48 – 0.292 (great for steep mountain trails!)
15/48 – 0.312 (the same as my old 14/45)
16/48 – 0.333 (the same as 14/42 that most people run)

Here is how to do this.

First, set up your workspace. I'm old and like having a lift so I don't have to bend over.

Take off the front sprocket cover and remove the 3 bolts holding on the sprocket securing plate, remove the securing plate

Then, since I'm replacing my old chain, I ground off the head of one of the chain rivet heads, then pushed it out using a Motion Pro chain tool that pushes out a pin, pushes on a side plate and rivets a rivet master link.

Next, remove the chain and take off the front sprocket. Then remove the rear wheel and unbolt the rear sprocket from the rear wheel hub. Here is the old chain and sprockets, and the new chain and sprockets:

The front sprocket held on with the circlip:

Next, I have to figure out how long the new chain should be cut down to. It has to fit all three front sprockets and have enough adjustment for both 14/48 and 16/48. It also has to have enough adjustment with 16/48 so that I can set the snail chain adjuster to zero and pull the sprocket off without breaking the chain. To do this, put on the combination that requires the greatest length, 16/48. It is easier to cut the chain shorter than to cut if longer if you make a mistake. Now, put the chain on , clamping one end to the back of the rear sprocket and pull it tight around the sprocket up to the end you have clamped off. Then, if the two links don't match so the new connecting link won't fit (as in the first picture), go to the next link longer and mark it as shown. Be sure the check that you can still slip off the front sprocket with the chain on it to verify the length.

Check adjustment for 16/48

Check adjustment for 14/48

Check that the sprocket will come off with this chain length:

Now that you know where the chain should be cut, grind off the rivet head, push out the pin and put it back on the bike.

Now, the chain has to be put back together. I have often run master links with the clip and they are fine. Just clean off the chain plate and put in a little silicone sealer to help hold in the clip (fish swimming in the direction of the chain movement!). But in this case, I am using a rivet master link. So, put on the inner O-rings, lube it up, and push it into the chain on the sprocket. Then put on the outer O-rings, lube, the push on the outer plate as hard as you can with your hand. This chain came with two handy spacers to keep the O-rings from getting squished.

Press on the outer plate with the chain tool.

Then, expand the rivets with the rivet tool. The Motion Pro too works great for all these chain jobs.

Raise/lower the bike to get the countershaft, swing arm pivot and rear axle to all line up. This will be the point where the chain will be tightest. Adjust so there is enough slack so the chain isn't tight at this point. Tighten down the axle nut and put in a cotter pin and you're done!

I now have my DR650 set up at 15/48 (0.312) as this is a great all-around around town gear ratio for me (the same as my old 14/45). If I am going to ride the bike over to Moab or somewhere farther away, I put the bike on the side stand and then take off the front sprocket cover and remove the circlip. Then, loosen the rear axle nut (don't have to remove the axle), push the rear wheel forward to slack the chain, and pull off the sprocket with the chain on it. Put on the 16T front sprocket, attaching the circlip with some pliers, adjust the chain with the snail adjusters and tighten the rear axle nut and I'm ready with 16/48 (0.333 - same as 14/42) gearing. Changing the gearing shouldn't take more than 10 minutes. When I get to my destination, I can replace the 16T with the 14T in 10 minutes and have 14/48 gearing (0.292 - 18.2% lower than stock!) for the trails. Switch back to ride home. Setting up your dual sport like this makes it a breeze to have the gearing you want and to be able to change it quickly and easily.
Pain in the Butte Ranch
Durango, Colorado

- Calculated risk or forbidden fruit?

FatChance screwed with this post 04-13-2010 at 03:38 PM
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