New to Forum - Help With DS650

Hi all, I am new to this forum, and purchased my first DS650 today.  I am pretty excited.  I just had a couple questions regarding it and hoped some of you might be able to help me out.  First off, it is a 2001 Baja.  The guy I bought it from fired it up for me, and I drove it around the yard.  It was hard to judge the sound of the engine because he had no muffler on it, but for some reason, when I got to 1/3 or more throttle, then engine would start to kick and sputter.... he told me he had just had the carb cleaned and done over, and that it had not been adjusted.  I was wondering what aspect of the carb would cause this, and what is the best way to go about getting it to run better.  He said once it warms up then it is better, but obviously something is up.  Apart from that, I already have the whole machine apart for maintenance and cleaning, is there anything else that is paramount to check before I drive this thing?  I am doing all fluids and filters this week, as well as grease and cleaning, but wasn't sure whether to get into valve lash and that kind of thing.   Thanks


PS - I am very experienced with engines and machines, but I have never worked with a Mikuni carb, so I am a little unsure.  

A Mikuni carb is really no different than any other brand.  They all work pretty much the same.  It worries me what else the guy had messed with if the thing has no exhaust (pretty typical of quad riders).  Removing the exhaust is going to cause a lean condition hence the sputtering.  Try a larger main jet or dropping the clip position on the needle.  Check out my how to videos for other tutorials and basic maintenance items on my website as well as "Like" my facebook page.

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Hello,
 Mikuni carbs are very easy to work with. Before you do you need to put an exhaust on the bike. Make sure that you have no vacuum leaks whatsoever.
 Hopefully, he didn't put in an overkill carburetor size on the engine. If so it will need jetting. Usually, the bigger the carb, the smaller the jets.
 1. The idle air screw always starts at 1 1/2 turns from closed. Let the engine warm up and open or close an 1/8 of a turn at a time. give it about 5 seconds to settle. Continue until the engine reaches it's highest RPM/speed. This is called your best lean idle.
 2. The cutaway on the slide regulates your mixture just off idle.
 3. The slow speed jet regulates the mixture until the needle in the slide takes over.
 4. The neddle in the slide regulates the mixture to wide open throttle. The needle has a taper to it which regulates the fuel amount from the main jet.
 5. The main jet regulates the mixture at "wide open" throttle.
 I have found that the best way to jet your engine is by what's called "seat of the pant's performance".
 Adjust the jet size by enriching the jet until you get the highest RPM/speed at that specific RPM/thottle position. An example would be the slow speed jet at lets say, 850-1000 RPM though this will change with the richer jet so actually it's better to go by slide position.
 The high speed jet you do by accelorating through the gears until you reach top end. Keep increasing the size one size at a time until you get the maximum speed and feel of power. Once that is reached go down one jet size.
 With different pipes and types of driving as well as types of intakes jetting will change. An example of intakes would be velocity stacks or air cleaner inside configurations. Different lenghts of these passages affect you RPM and acceloration. High performance demand will always require richer mixtures as moderate driving will perform better at leaner mixtures.
Good luck.