Hey all, I have read a lot about jetting and setting up the carb on my DS650. It is a 2001 and I have only had it for a month or so. I only got to drive it once so far, but I have done everything over on it to get it running really well. Everything is stock on the bike, with the exception of the exhaust. The stock muffler was totally shot, so I welded in a small tractor muffler. It works really well and I am just trail riding, no racing. The muffler is a straight through with steel baffles and about a 2" or less pipe. (smaller than the original).

When I took the bike riding, I started it with the idle mixture adjustment out 2 turns. I warmed it up, and started to open it up until the revs started to come up, and until it stopped popping when I reved it up high. I found the point where it pretty much wanted to be at about 7 turns open. I feel like this is excessive, and after about an hour of riding my plugs have some whiteness to them. I checked my jets and they are all stock, (165). Is the 7 turns open an indication that I need to go up a jet size or 2? I feel like just an exhaust change shouldnt have THAT much of an effect, but then again I dont know how many turns of the mixture screw is reasonable. Thanks for any advice.

jdschwass

 

first I would putt a proper pipe on it. what $50 ? I have one if you need one.

2nd the screw is only for idle ... and yes 7 turns out the screw will fall out and your in a new bucket of fun.

if you stay the same pipe go up to a 175 or 180 main jet ....

 

Thanks for the reply. I would prefer not to change the pipe simply because of money, and I dont think it is affecting the performance negatively too much, it even sounds really nice. In the future this may be an option for me. I have ordered the dynojet kit for it (stage 1 and 3). I was going to try putting in the stage 1 kit with the 180, which is what the dynojet instructions recommended for stock intake and slip-on exhaust. I am glad that you advised the same. I know the mixture screw is only for the idle mixture, but the fact that it needs to be out 7 turns to idle properly means it must be running lean all around right? I moved the slide clip to pos.5 (stock is 4) which helped a bit in the mid range, but I just feel like the high end is limited as well, it just doesn't want to GO, if you know what I mean. Mind you, I drove it in about 5 inches of snow, so it was hard to tell when it was pulling well due to slippage. Hopefully the stage 1 kit helps. As well, the "stock" filter ordered from royal is a UNI filter, and I have read that they are slightly easier breathing then real stock, so this may be affecting me as well.

 

im not sure if the carb is the same as a 2stroke but on mine theres 3 jets to adjust for diffrent ranges the pilot jet regulates the idle then theres the needle witch controls midrange and your main that covers top end If your problem is at idle the main jet wouldn't effect the idle you would need to change the pilot jet it controls the idle circuit

 

Let me know if I'm wrong, but the way I see it is that if you make a change to the engine that causes it to run lean at an idle, then chances are it is running lean through the mid and high end as well right? I think the stage 1 will help, but I didnt consider changing the pilot, its not a bad idea. I think the stock pilot is a 40 right? What would be the next size to try? The only difference changing the pilot will be is that I can run the same fuel/air mixture with fewer turns open on the screw right? Thanks.

 

Okay, so I have ordered a new pilot. Based on advice in the stock carb mod post, I am going to put in a 47.5. I read in another post that cold starts can be tough with a pilot too small, and I definitely notice that. I was out in -10 cel, and with full choke it would start well but would die if I gave it throttle until I let it idle for a minute, and thats with the idle screw opened right up. Hopefully this will will solve that problem and allow me to close up the mixture screw a whole bunch.

 

Your correct it will lean through all the jets. the needle should be able to correct your midrange and topend but you may need go up a size on your mainjet also. I would try moving the clip on the needle down it will richen it. And yes you will need to reset your screw and start again

 

Ok great, I'm starting to get a good understanding of this. I already dropped the clip to the bottom slot on the pin, since the 4th is stock, there is not a lot of room to richen in the mid range. Once i get all my parts in the mail, I am going to be adding the 47.5 pilot with the dynojet stage 1 kit, which includes a new needle, and will likely start out with a 180 main. Really hoping this helps, because the bike just wasn't meeting performance expectations I had in mind. It is my first time driving a real racing quad so I cant really compare, but definitely seemed to be lacking, especially in the higher end range. Thanks for everyone's help, I will post back when I get the thing back together.

Unfortunately I cant start it until I get my new water pump pinion which has to be ordered from Germany.... they said give it 2-3 weeks!

jdschwass