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2000 DR-Z400S carb problems

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I just picked up this bike with 5000 miles on it and it spent the last three years sitting in this guys garage. Originally it would start with the choke, but wouldn't idle without the choke. It's got the Mikuni BSR36. Obviously something was clogged up in the pilot jet system. I took the carb off and did a thorough cleaning, then adjusted the fuel screw until it now idles beautifully. Here's the problem now. Up to an 1/8, possibly a 1/4 throttle, it will rev up to several thousand rpms, but after that the engine sputters. If I put the throttle at around 3/4 there is a rhythmic up and down in the rpms. There is also almost no power and the bike instantly stalls when I try to put it into gear. Would love some suggestions on what might be the problem.

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What is the jetting? Is the air filter clean? New spark plug? Please give us some more info.

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Take a close look at the slide diaphragm for tears or punctures. Verify the small "O" ring under the top cap is there. Verify the needle is retained in the slide and verily the spacers on the needle are installed correctly.

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This guy was the original owner, everything is stock. He replaced the spark plug once, but I haven't taken it out to look at it (probably would be a good idea). The diaphragm looks good and the O ring is there. I don't think the carb has ever been taken apart, but honestly I don't know how to tell if the spacers on the needle are installed correctly. The air filter looks good, but I tried taking it out to see if there was any change and there wasn't.

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Ok I see, Check out this video and speed it up to 4:15, This shows you the layout of the needle.

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While your in there I would go ahead and do the 3x3 air box mod and re-jet with a JD Jet kit. 3 years is a long time for varnish to set so a good soaking in a quality carb cleaner would help.

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