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I bought a used 2001 400EX a few weeks ago. I have ridden ATVs since I was a kid but never owned one. Anyways I am not really familiar with small engines so I am hoping someone can help with a couple things I have noticed. I want to start off by saying that I love the new quad. It rides great fires right up and is a ton of fun. Now to the issues.

First off I recently noticed that when neutral if I rack on the throttle it cuts out for a second before revving up. However when I am riding there is no issue it goes through all five gears with no problems and accelerates smoothly. What could be causing this? Is it something I should be overly concerned with since it doesn't happen when I am riding?

Secondly I was looking it over the other day after it had sat for a week or so and noticed there was some fuel on the outside of the carb. It wasn't dripping or anything, the carb and one of the tubes coming out were just wet and when I touched it I could smell the fuel. My question is would this indicate that the gaskets need to be replaced or the hoses possibly? Also is this something I should worry about since it seems to run fine and I have never noticed fuel dripping off or anything? Could this problem be related to my first problem?

Background on the Quad. Like I said its a 2001 400EX with an hmf slip on, a K&N air filter, and has been jetted. The rest of the quad is stock. All of this comes from the previous owner so I don't know for sure that it is jetted because I have never taken apart the carb.
 

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First, the throttle lag or hesitation when in neutral is caused by a momentary loss of vacuum caused by the sudden opening of the throttle. The engine coughs due to the suddenly lean condition. The slight hesitation of the engine allows the velocity of the air through the venturi of the carb to "catch up" and the engine revs normally. This problem may be alleviated by, increasing the idle speed, installing a smaller carb, lightening the crankshaft and flywheel or installing a performance carb with an accelerator pump.

Second, fuel on the outside of the carb might indicate a failing gasket, but usually can be fixed by shutting the petcock off when you park the machine. When the fuel is left on, it will vaporize to the atmosphere through the float bowl vents. Some of the vapors will condense in the lines or on the surface of the outside of the carb. Try shutting the fuel off and the problem will probably go away. Don't worry about it.

Suggestion, get rid of the K&N filter and install a foam filter. K&N's flow more air and more dirt too. If you need maximum performance and don't mind rebuilding the engine at least once a year, then keep the K&N. I run a stock Honda filter in mine and service it after each dusty ride. I've only had to rebuild my motor twice since 2004 and they were scheduled rebuilds - not because it quit running or worse. Also, change the oil and filter at least once a month and use motorcycle approved grade oil (JASO rated MA or MA2 or API rated SJ, SH, SG, SF, SE or SD)
 
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