By: Michael Allen And Kris Keefer
It’s no secret that Doug Dubach knows Yamahas. That being said, after years of testing for Yamaha Doug started Dubach Racing Development where he builds finely tuned exhaust systems for other major motocross models. However, this isn’t one of those “other” motorcycles and we wanted to take that atrocious sounding stock muffler and try something we haven’t tried. I met Doug through Kris and have had the privilege of hearing some old testing stories, listening to him give Kris shit, giving me the basic inner workings of exhausts and testing in general explained to me. I really look up to Doug and Kris’s testing abilities both, so when they sent me a DR.D system to try on the 2021 YZ 250F, I was excited and nervous at the same time. Excited because if anyone knows how to make a Yamaha work well its Doug. Nervous because I knew the exhaust wasn’t the only thing being evaluated; Kris always expects me to go into any test with no pre conceived notions about the product and he’s always evaluating my ability to test which is a bit nerve racking.
It’s no secret that the Yamaha YZ 250F has a damn good production engine. When the bike was redesigned in 2019, the power characteristics of the engine slightly changed from making the majority of its power lower in the RPM range, to slightly shifting the peak power up in the RPM range giving the bike a lighter, free revving feeling. While this more playful feeling is fun to use, there was still a part of me that missed the low-end grunt of the previous engine character. After Randy Richardson gave the bike a proper break-in at the Dubya USA World Vet Nationals, the stock muffler packing was extremely blown out, there was seemingly no packing left in the can. I love doing back to back testing because the difference in performance (good or bad) of a product will be far more obvious if the comparison is made the same day. So when at Glen Helen racing the Swap Moto Series I decided to race the first moto with the blown out stock muffler, and the second moto with the DR. D system.
Although some people may think that since the exhaust wraps around the engine it must be a pain to change it was very straight forward. There was only one step that I found I needed help with to make the process easier, which involved my wife, her butt and me asking for her to sit on it….. With the stock system removed, I simply needed my wife to sit on the bike so that the shock would compress and move back enough in order to get the head pipe between the frame, shock and engine. One other tip is to tighten the two exhaust stud bolts before installing the muffler because leaving the muffler off allows for more room for a wrench. Aside from that step, leave all the bolts finger tight until all the parts are installed, so that there is a little wiggle room.
After racing moto one I’m sure most of the spectators ears were pleased when I rolled up for the second moto with a fresh exhaust. The first thing I noticed was the change in the exhaust note, gone was the raspy clapped out tone that bellowed from the rear end of the 2021 machine. That raspyness had been replaced by a more throaty sound that obviously had more backpressure and sounded crisp. As the man in overalls ran back to the doghouse to drop the gate I focused solely on my technique and to my surprise when the gate fell I instantly felt far more connectivity from my throttle hand to the rear wheel. I got a great jump, and stayed right with the KTM 350 that was next to me until about half way through third gear. It doesn’t matter what exhaust you have, nothing is going to make up for 100ccs, not to mention all the 450 machines in my class. In addition to the improved connectivity, the power with the new system has been smoothed out. Don’t let that be confused with mellowed out; in fact the DR.D system has noticeably more mid to top end over stock, yet also gave me a little more low end that I wanted back from the Yamaha. Instead of just making noise and spinning, the bike is now able to put that power to the ground and drive forward. The DR.D system not only helps get the power to the ground, it helps clean up some of the FI setting near the low end range on slower corners. I felt like the NS-4 muffler brought some added mid range meat to third gear and allowed me to make my shifting points later than the stock system did.
To be honest, most manufacturers in 2021 make very good stock exhaust systems that don’t leave much room for improvement. When it comes to performance gains over the blown out stock system, this DR.D full system surprised the hell out of me and I think an exhaust shootout may be in order soon. With a price tag of $659.95 this stainless and aluminum system is a great deal when compared to the price of other manufacturers and is still lighter than stock by over a pound. It may not be the lightest thing on the market, but let’s get real, you and I don’t need the weight loss on our machines. Maybe I need to lose a few before my machine. Once again Doug proved that during all those years helping develop Yamaha’s YZ’s he was taking notes on what works and what doesn’t. If you have any questions about the 2021 YZ 250F DR.D exhaust system, reach out to me at Michael@keeferinctesting.com.
You can get a DR.D muffler system over at www.dubachracing.com.
Keefer’s Notes:
I concur on what Michael has written and would like to add that to me the bottom end character is improved with the DR.D on. The bottom to mid RPM response is not only better but to me gives the rider more control around the track. Michael mentioned being more connected to the rear wheel and that right there is what I noticed the most.