Ok, so I have a friend that was given a DS 650 (not sure year). It was set up and tuned as a race bike, and it's all of that. However, he wanted it a little more tame and quieter. So they had a "standard" pipe put back on it and a local shop "tunned" it for him. After that, it would run, and had a good low and top end but the mid band would just a dog. They had to put a new battery in it and it just wouldn't seem to hold a charge. Needless to say it's been sitting a while now.

So I said I'de help. I'm not the smartest guys in the world, but I can find my way around a garage. I can somewhat tune a needled carb, but have never messed with jets.

I took a look at it the other night and when I got there they had fueled the bike up and gas was dripping out of the bowl. I fiddled with it a bit but could not get it to stop leaking. Is there supposed to be a hose hooked to the little bowl drain pipe? Opening the screw will let us flow pretty good, but it never stops. I'll get that fixed even if I have to plug the pipe.

Then as I walk around the bike to the right side I see fuel dripping on to the rear shock. I popped the seat and opened the air box and it was full of fuel.

I showed them where the petcock was to turn the fuel off and they said that they never have used it, it's always turned on. Could a constant flow of fuel into the carb over a year or so have ruined the carb?

So for giggles I tried to start and it was DEAD after 2 hours on the charger. So we tried to jump it, and it wouldn't even crank. So I told them it would have to be a winter project.

I got a guys at work who's probably smarter than anyone I know on engines. He's ready to just put an O2 sensor in the pipe and tune it right he says. "It takes all the guess work out" he says. I agree, but do I have to go through all of that or is there an easier way?

Regardless I told my friend that it would have to be a winter project, but any help I can get in the meantime would be great.

did you pull the plug and see if cylinder was full of fuel. i have a problem on my mower if i don't shut off fuel it floods the cyl. and you can;t jump it. acts like dead battery but actually full of fuel.

Leaving the fuel on will not ruin the carb, it sounds like the carb needs to be rebuilt. Most likly the needle and seat are stuck and not shutting of the fuel when the bowl is full. I beleive you are describing the carb vent that has fuel coming out. You should not block that off. Your coworker is correct about tuning with the O2 sensors, but you need a working carb before you can start to tune. As far as the battery goes if it didn't take a charge its probably bad.

Thanks guys. I'll get it over here and get it apart and clean it real good. I'll also pull the plugs to see what kind of condition they're in, more than likely change them just for the sake of ruling out things. For that matter I'll also throw a new battery in too since I'm sure that it's pretty shot. I'm just suprised that it wouldn't even crank when we tried to jump it.

Now from what I understand, that carb has three settings correct? So you think that the vent is the little tube coming straight out of the bottom? I guess I can see the logic in this, maybe this is they the airbox was full of fuel too, ah?

Thanks guys, I'll keep you updated.

Ok, so I've made some headway. I tore the carb apart and sure enough she was pretty ugly inside. A lot of the brass jets were all coroded. I pulled all the jets and blew cab cleaner through every passage I could find. Put it all back together, no more leaking, YAY. Pulled the battery and put it on the trickle charger and scabbed another battery on for testing.

She fired right up, but LOUD, holy cow that thing's got a pipe on it!

So I tried disconnecting the battery and she died. So I assume the charging system's like some motorcycles where you have to have a battery in order to run. So I'm thinking that with a weak or poor batter, it will not run well.

The carb had three internal jets inside the bowl. One with a very small passage toward the intake side of the carb, one off to the side, then one toward the engine side that was tucked inside a small brass barrell that when removed goes straight through and is controlled by the large needle that comes down through the carb from the upper diaphram.

I'm assuming the small jet towards the intake is the idle jet and the large one with the barrell around it is the main jet. Process of elimination would leave the one to the side as the mid range jet. Correct? These are all assumprions on my part, so correct where necessary.

Now it seems to run fine, once warm. However, there still seems to be a dead spot in the RPM range. Kind of like it loses power in the middle somwhere.

I pulled the plugs and they were pitch BLACK, I mean bigtime fouled. So I cleaned them up with a wire brush and put them back in. I ran it for a little bit last night just to put some time on it. (I'm sure the neighbor's are cusing me with that pipe on it running up and down the street. I'll pull the plugs again today to see what shape they're in. Because they could have been fouled from the more restricted pipe that they threw on it to quiet her down.

So I assume it's running rich because of the plugs. How long will it take running to take another look at the plugs? Or should I assume that there's a jetting issue because of the mid-band performance?

Oh, and there was a small needle screw just under the engine side of the intake. It was forward of the bowl and from what I could tell was about 1.5 turns off of bottoming out. Not sure that this is for.

Thanks guys for the help.

Your getting there. I would go through and clean the carbs again. The hesitation that you are getting in the mid rpm area is from the pilot jet. The main jet is the one that your described. The other jet that is in the carb is the one that is a pain to clean. I would take everyything apart and let it soak in parts washing solution over night. Then take an air compressor and blow all the jet and the passage ways in the carb out with compressed air. I still think it is the carb gunked up thats giving you issues.