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Hi all, I'm new here. Bought a 95 sportsman 400 4x4 last year. I rebuilt the carb last weekend and finally got it running again. My problem is I took it for a test ride (to end of street and back) and upon return the idle started to increase faster and faster to where it was full idle. I had to kill the engine by shutting off the kill switch, turn key off then hold throttle switch wide open to flood it. What do I need to look at to fix this problem. It didn't do this before i rebuilt the carb. Thanks for any help!
 

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It may have to do partly with how you removed and installed the carb - what parts did you remove to remove the carb?

A two stroke can "run away" due to an air leak or air mixing with the fuel before it enters the venturi of the carb. In essence it is dieseling and killing the spark will not shut it down. Generally just opening the throttle completely leans it out enough to cause it to starve for fuel and die.

If there is not a crack or split in the carb holder, I would first check the float level in the carb, make sure the floats move freely on their guide pins and that the guide pins were not accidentally bent and no longer perpendicular to the upper part of the carb. If the carb checks out, then pressurize the crankcase to check the condition of the crank seals. Make sure the oil injection line is connected and in good condition (a split in the oil injection line could result in an air leak). Make sure the fuel is fresh and 87 or higher octane (89 or higher if blended with ethanol). Verify the spark plug is the correct heat range or colder than recommended. Engine modifications dictate using a colder than recommended heat range spark plug. Make sure the carb was full of of fuel and that the fuel level was not dropping as it was being ridden. Make sure the fuel tank is vented and not operating under a vacuum.
 
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