Looking to smooth out the power band, it seems to have a dip at about 3000rpm and the takes off at about 4000rpm. Would an exhaust do the trick, trying to avoid carb work.

 

Probably jetting... sorry to say.

 

You think it is the jetting, the quad is bone stock.

 

Jetting is affected by altitude and airflow(to the carb) too... If either has changed, that may be the problem.


Has it always done this since new?

 

well if its bone stock i'd say its the crappy stock exhaust tip, it has very dissapointing bottom end wit that cap

 

Yes it is bone stock , and has done it since the first ride. I was hoping that I could change exhaust to solve the problem. How difficult is rejetting?

 

I suggest trying a new exhaust, or better yet just buy the billtet aluminum tip for the stocker which is cheaper and works great. No matter what type of exhaust you decide to run, you will need to change your jetting. If you don't change your jetting you wont have anywhere near the full power increase of the exhaust and you'll be running your engine lean which runs the risk of damage.

Rejetting is not too difficult on a DS650, do a search on the word jetting - you'll find pages and pages on how to do it. take lots of notes, then do it. The hardest part about jetting the stock DS carb. is getting the float bowl off. Do a search on that as well. I knew when I bought my second DS (2003 Baja. much like yours) that the hardest thing to do was get the float bowl off so I did that first. Now jetting takes about five minutes if I'l prepared.

On every dyno sheet I've ever seen of a bone stock DS they all have a dip in the power band much like you describe. Then you feel a huge hit of power as it turns back on. On all decent pipes you'll see a much smoother powerband without the dip. The better exhausts do more than just remove that little bump! The poorer performing ones do only a little more than remove the power dive in the 3000 RPM range. Choose wisely.

Take a look at my pictures page, you can see the billet end cap I have as well as a dyno sheet for it.

 

I really isn't a dip in horsepower that you feel, it's a dip in torque. The horsepower is still rising, just not as fast as the rest of the curve. THE billet end cap makes 6 ft lb more torque at 3000rpm, 9 ft-lb more at 3500 rpm, and keeps a nice spread up to 6300 rpm.

The stock endcap makes its lowest amount of torque at 2700-3700rpm range. THE billet endcap makes its peak torque from 3000 to 6300 rpm (nice and flat) so you can imagine the night and day difference in the seat of your pants.

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When I first got my DS, the power band was only strong between 4000-6000. I added the HMF and K&N jet kit, and it came on strong from idle (about 1500) until 7100. Later I removed the air box lid and snorkels, and got even more power that lasted all the way up to the 7900 rev limit.
The reason I went with HMF instead of the end cap is that I was able to get the quiet core and spark arrestor in case I wanted to go to the woods.

 

I spent a gooood long (AND FUN!) weekend at Glamis using my end cap and here are my thoughts: it has given my bike awesome low end response. When I blip the throttle it jumps forward and makes getting the front end up easy so I can now easily get the front end over bumps or ruts or whatever it is I don't want the front tires to hit. I was also thinking about the whole spark arrester thing myself and this is my conclusion: If I need it to be quiet, or spark arrested, what is easier than unscrewing two screws, swapping the billet end cap for stock and then re-installing the two screws. I don't think it gets easier than that.