Originally Posted by jimmyboris
My project is to take apart my dr and rebuild it. Why??
the engine has 16000 miles on it with full service history, but the bike is looking like it would benefit from a make over. i wasnt intending to do anything with the engine...although....
why not see if i can increase the power somehow. there is a k&n filter on it. i know i can put an exhaust but the power gained is
...surely there is something i can do to the engine or carb. any thoughts people...im starting this project after chritmas and will be keeping records and photos as i go. im in no rush to do it.
The big questions are:
How much power do you want?
How much are you prepared to spend?
The DR650SE comes from the factory running REALLY weak (about 35WHP) and really rough compared to how it CAN run. You may not even realize just how poorly a stock DR runs until you start experimenting. Some people are getting over 50WHP from a DR650SE, but you may not need anywhere near that much. Just getting the bike to run smoothly, and improving the throttle response, can make the bike seem like it's putting out WAY more power, when it may be just a minimal increase that is delivered better.
The stock exhaust isn't a huge problem for power until you upgrade other things. Most people swap it out because it is a heavy boat anchor and/or they're looking for more power. More power is possible with it still bolted in place though, but it IS a bit limiting if one is going for big increases, especially the blob of weld that is usually in the header pipe. Many people grind this blob smooth for better flow.
The big initial limiters on power with the DR650SE are the stock airbox and the jetting that is extremely lean for use at/near sea level. Opening up the airbox by removing the snorkel, cutting the top, or cutting/removing the sidecover will allow the engine to breathe much easier. To better take advantage of this airflow though, you'll also want to jet the carb a bit richer. At the same time, you can improve throttle response by drilling a 2nd hole in the slide and/or trimming a slight amount off the slide spring. Research this heavily before doing so though. There is a point of diminishing or negative returns. Once these mods are made, THEN the stock exhaust will start to become a limiting factor.
I recently swapped in a richer main jet, cut the top of my airbox, swapped in an adjustable pilot needle, and swapped in an extended idle mixture screw. I still have the stock header pipe and haven't ground the weld smooth, but I do have an FMF Q2 free-flowing muffler and midpipe (light, loud w/heavy throttle, quiet w/light throttle, needs occasional repacking). My stock pilot jet seems a bit rich right now, but other than that, my DR runs WAY better than it did with the stock main jet, the stock idle mix screw, and a KTM adjustable needle paired with this FMF exhaust and an airbox with a few small holes cut. It now idles smoothly, pulls 5th gear smoothly from 45MPH indicated, spans the wide-ratio tranny gearing MUCH better, pops the front wheel up easily in 1st and 2nd with no clutch or tugging, and pulls like a freight train with a passenger and luggage aboard...from idle to well beyond any legal speed in this country. I also still seem to be getting about 50MPG (US).
I WOULD like to swap this FMF Q2 muffler to a 2001/2002 GSX-R1000 titanium muffler, as it flows about the same but is slightly quieter, slightly lighter, and never needs repacking.
I'm now curious how powerful this thing would feel with a flatslide pumper carb, a 780cc big-bore kit, a big-valve head, a Webcams 223 cam, and a sprocket change. That would be well into 50+WHP territory, and I haven't even mentioned forced induction or nitrous yet. (Yes, there ARE a few people experimenting with that stuff, and a mfr HAS actually brought a turbo kit to market for the smaller Yamaha WR250R/X...so it COULD potentially be done. There are also a few people currently adapting/experimenting EFI on the DR.)
Google "Procycle" and "Kientech" to find performance parts and more info for your DR. They both offer a LOT of info over the phone or web.