If the DRZ has an Achilles Heel when used as a dual sport adventure bike it is the narrow ratio transmission. My riding consists of a mix of paved and non-paved roads and, as any DRZ owner will confirm, you just can’t get the right sprockets on the DRZ to meet the need. If you gear the bike so that it can comfortably run highway speeds (up to 70 mph) then it is geared much too high for serious dirt riding. Conversely, if you gear it low for the dirt then the engine will really be screaming (running high RPMs) at highway speeds. Suzuki recognizes this issue because the street-only SM model (the supermoto) comes stock with 15/41 front/rear sprocket combo while the off-road only E model comes with 14/47 – equivalent to a 9 tooth difference on the rear sprocket just to make the bike good at either pavement only or dirt only. As a point of comparison Kawasaki KLR riders will often change the front sprocket size by 1 tooth in order to bias the KLR toward dirt or street, which is a far cry from the DRZ needing an equivalent 9 tooth change in order to make it suitable for dirt or street duty.
The stock DRZ S model tries to split the difference between the E and SM models by running a 15/44 sprocket combo, resulting in gearing that is simultaneously a bit too high for tough dirt riding and too low for sustained highway speeds. In stock form, the S model is good for easier dirt riding and for highway speeds up to about 55-60 mph. If your riding consists of backroads and moderate dirt, then the stock DRZ transmission is just fine. However, if you want a bike that can do both harder dirt riding and sustained highway riding at 70 mph then the DRZ transmission is sadly lacking.
This reason, more than any other, kept the DRZ off my list of possible dual sport adventure bikes. Then a friend alerted me that Advanced Clutch Technology (ACT) had come out with a wide ratio transmission for the DRZ and the idea was planted in my brain – build a true dual sport adventure out of the DRZ. I decided to buy a DRZ, add the ACT wide ratio transmission and a big bore kit, and build the bike Suzuki should already be making. I started doing some internet research to learn more about the ACT gears.
A search on the DRZ forum on Thumper Talk revealed some interesting information. The ACT gearset only changes 2nd through 5th gear; 1st gear remains stock. It spreads the distance between 1st and 2nd gears 6.6%, with increasingly wider gaps at higher gears.
The owner of ACT posted some RPM/Speed charts on Thumper Talk to give riders an idea of the difference between a stock DRZ and one with the ACT gears installed. As you can see in the first chart above, if you are running 15/44 sprockets then with the ACT gears you are just shifting into 5th gear at about the same speed where you maxed out the stock DRZ in 5th gear. In real life, at about 60 mph on the stock DRZ your engine would be reving pretty high and would be quite buzzy (lots of vibration). With the new ACT wide ratio gears you are shifting into 5th about 60 mph and are able to run 80 mph at significantly lower RPMs and engine vibration.
Recall, however, that with the stock 15/44 sprockets you are geared too high for serious dirt work. Instead, the 14/47 combo that comes stock on the E model is a better choice for dirt riding. Would the ACT gears allow you to run 14/47 to meet your dirt needs but still provide a high enough 5th gear for highway speeds? That would be the ideal solution. The 2nd chart above provides the answer to that question – yes, you can. Even with a 14/47 combo 5th gear is still higher than a stock DRZ S model running the 15/44 sprocket combo.
After examining the ACT info I decided they would likely work very well in an adventure bike and that this could be a really fun project. I found a 2003 S model and began the build process. Luckily noted DRZ expert Erik Marquez lives less than two hours from me so I asked him to do the engine work for me. He installed the ACT transmission, a Cylinder Works big bore kit plus all the recommended “loctite fixes” for the DRZ.
Prior to beginning this project I had two concerns. First was that the stock engine would be underpowered with the wide ratio transmission and would be unable to pull 5th gear effectively. The second concern was that the gap between 1st and 2nd gears would be too large for serious dirt riding.
In order to address my first concern I added a big bore kit from Cylinder Works. My thought process was that the big bore kit would compensate for the reduction in acceleration from the wide ratio transmission. I will address this concern in detail during my discussion of the big bore kit later on. For now, know that the this particular concern is a non-issue.
My second concern was that the gap between 1st and 2nd gears would be too wide. If you’ve ever ridden a stock KLR or XR650L then you know both of those bikes have a too-large gap between 1st and 2nd. When riding in more difficult terrain you will often find yourself either running too high RPMs in 1st gear or too low RPMs in 2nd gear. It becomes even more noticeable when riding uphill in difficult terrain – 1st can easily be too slow for the best climbing speed but 2nd gear will be too fast for the terrain.
The stock DRZ transmission is perfect for serious dirt riding if you are running the appropriate sprockets. When riding off-road the transmission’s narrow gear ratios mean that you can always find the right gear for the conditions you are riding in and your skill level. A wider ratio transmission can make serious dirt riding more challenging if the gear ratios are too-wide.
After testing the ACT gearset in the mountains of northeast Mexico I was happy to confirm that the gap between the ACT wide ratio gears is not excessively large. While the gap between 1st and 2nd is noticeably wider with the ACT gearset than the stock DRZ, it is not so large as to make the bike less capable on challenging terrain. During my ride in Mexico I rode some fairly steep terrain (pictured above) and never felt like I was in a situation where 1st gear was too low but 2nd gear was too high.
The one thing I did notice during the initial break-in miles was that the gap between 4th and 5th gears is pretty large. The concern with this was the same as with a too-large gap between 1st and 2nd. Would I find myself in situations where I was going too fast for 4th gear but too slow to be in 5th gear? Or would I find situations, such as long uphill sections, where I didn’t have enough power to stay in 5th gear and would have to downshift to 4th to make it to the top?
I can faithfully report that, for me and the type of riding I have done on the bike to date, the gap between 4th and 5th is not too large. I have yet to find myself in a situation where I just couldn’t make either 4th or 5th gear work for me.
That being said, I don’t live in the mountains and, therefore, don’t have many opportunities to ride long or steep uphill pavement sections. I also don’t live in the desert where I might find myself running 50-60 mph cross country. In those situations you might find the gap between 4th and 5th less than perfect for your needs. I just don’t know for sure.
In any case, for the type of riding I do, I much prefer a larger gap between 4th and 5th than between 1st and 2nd (or 2nd and 3rd). As they say, YMMV.