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520sx Stumbles At Steady Throttle

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Well, I am still working on this 520 :cry: It still has a bad stumble at steady RPM. Following is a list of things I've checked/tried.

Multiple Carb settings:


NEEDLE:ODBTM/JD Red Needle, multiple positions with the above mentioned MJs.

Idle Jet: 50(not sure why it doesn't have the 48)

Air Jets: 200/100

Starting Jet: 85

Mixture Screw Open 1 turn.

There are no air leaks between the carb and engine. The carb is clean, I've completly disassembled and cleaned it three times. Adjusted the valves. Checked auto-decompression bolt. Disconnected TPS. Changed plug/checked plug wire(spark plug is always smut black, no smoke). The only thing that ever changed anything is the needle position. The lower the needle(higher the clip) the later in the throttle range the engine starts to sputter. I set up the Carb per JD jet kit instructions but nothing changed. I've been trying to figure this thing out for a couple months off and on. The problem has never went away. The bike starts, idles and accelerates great. It is only at steady throttle that the engine stumbles.

If anyone has ANY ideas I'd really appreciate it.

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