Converting the DRZ400K into a SuperMoto

in DRZ400, howto, supermoto

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The conversion was pretty simple since I already had a Baja Designs dual sport kit installed on it. The most time consuming part was building the wheels. I decided to save a few bucks and re-use the original hubs and lace smaller rims to them. I ordered the stock rim and spoke kit from the DRZ400SM since both the K and the SM use the same hubs. I measured the amount of dish the rims should have on an SM to make sure I had the geometry correct when building the wheels.

Once you have the parts together simply cut the old spokes out of the wheel to remove the dirt rims or, if you want to save them take the time to unscrew them. Clean up the old hubs well now that they're easy to get to. I also replaced the seals while I was at it. The original bearings were still fine.

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If you have never laced up a set of rims, I don't recommend trying this without supervision by somebody who knows what they are doing. It's not particularly hard to do, but you do have to be precise. I would suggest tearing apart and reassembling some bicycle wheels for practice. Motorcycle rims are actually easier to lace than bicycle rims since the spokes will only fit in one way. Start by dropping the spokes that get pulled in one direction only on one side of the hub. Lace those up. Flip the wheel over and drop in the spokes that pull in the opposite direction on the other side of the hub. Once you have those in place lace up the remaining spokes.

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Make sure to lube up the nipples well and begin tightening the spokes. Tighten them about a turn at a time till they all get snug.. moving from one to the other after each single turn. Once they are snug you will need to true them and make sure the spokes are at the correct torque setting. There is a special spoke torque wrench that is available for this. You may also use a standard torque wrench with a slotted screw driver bit on the end of it. I mounted the wheels on the bike to true them up. Tape a stiff wire or coat hanger to the forks or swingarm so that it will just about touch the rim when the rim is trued correctly.

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The Bicycle Wheel 3rd Edition I recommend this book if you've never built a spoked wheel before.

After truing up the wheels mount your tires of choice. Make sure you have the appropriate sized rim strip. If you don't have one, you can make one out of an old inner tube. Cut the tube so it's just wide enough to fit in the valley where the spokes seat on the rim. Wrap it around the rim and glue the ends together. Use a hole punch to cut a hole for the valve to stick through.

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I went with some pretty tall gearing. 38 rear and 15 front.

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Next was to replace the springs. Remove the rear subframe to get to the shock. On the DRZ it's a fairly basic procedure so I didn't bother taking pics.

Loosen the compression on the shock before actually removing the shock from the bike. It's easier that way. I thought about revalving the shock, but decided to take a chance. The stock shock seems to do fine, but is at the end of it's damping adjustability with the heavier springs and higher speeds of supermoto. Once you have the spring loose, lift it up off the seat and pull the seat up. You'll see a small wire ring that holds the spring seat in place.

Remove this ring.

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Now the seat should clear the shock and the spring may be swapped.

Reinstall the shock and get your sag close before bolting the subframe back up. It's just easier that way.

I then swapped out the fork springs. I opted to use the stock fluid and see if the adjustments would be within range before messing around with different weights or gold valves. The front forks still have a bit of adjustment left after I tweaked them to my liking.

Remove the bolts holding the handlebar on and move the handlebar out of the way. Work on one fork leg at a time unless the bike is on a stand.

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Loosen the pinchbolt on the clamp at the top of the fork leg. Trust me, you don't want to try and remove the fork cap while the pinch bolts are tight. Remove the fork cap. Pull the spring up and out of the fork as much as possible. It won't come all the way out just yet. What you need to do is slide a wrench onto the nut on the back side of the cap and loosen it from the damping rod.

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Mount your wheels, install the correct length chain and you're good. That's the basics for a SM conversion. I'll be adding bigger front brakes this winter. The stock front brakes just don't quite cut it. You can do a stoppie, but the lever has to be squeezed as hard as you can and it travels all the way to the grip to get it done. Not ideal for modulation control.

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