250 problems

Hey I have some problems I wanna go over on my atv. I know this is a dirt bike forum but you guys know a lot and are a huge help, and there's not much of a difference between atvs and dirt bikes. Anyways, I just bought this 2004 Suzuki LT-Z250 quadsport. Ton of fun to ride! When I bought it, the guy before me took the muffler off and cut the tip off, then took all the insulation and everything out of it and welded the tip back... the quad wouldn't idle anymore because of that. So I bought a new oem muffler and replaced it. I took the carb off and inspected it, super clean. I changed the oil and oil filter. I cleaned the air filter. I installed a new spark plug. Here's the problems I'm having: I got it to idle, however when it's in neutral and I give it throttle, it kind of hangs a bit in the lower rpms and the quad shakes and rattles. When I put it in first or anything, it idles normal and runs smooth. Next problem: the engine is heating up too quickly? I'm not sure if this is normal or not but the engine gets real hot real fast. I can feel it radiating hot onto my legs just a couple minutes of idling. Last problem: it pops a lot on deceleration. When I let off the throttle it'll start popping.
 
your idle issue is more than likely either float height or accelerator pump.
Heat thing I wouldn't worry about unless its severe (aka boiling the radiators)
 
your idle issue is more than likely either float height or accelerator pump.
Heat thing I wouldn't worry about unless its severe (aka boiling the radiators)
There are no radiators so I wouldn't be able to tell. Also what do you mean float height? And what's causing this popping?
 
Also what do you mean float height?
He is referring to the float valve in the carburetor. There is a float in your carb bowl that works very much like the float valve in your toilet bowl. It basically regulates how much fuel enters the carb. If it's too high you get a rich condition, too low a lean condition.
Running hot and popping can be because of a lean condition.
What does your spark plug look like? Got any photos of it?
 
I thought you couldn't adjust your float height? I thought they were at a set height?
They have a recommended set height, but they're typically adjustable.
If you just purchased this thing it might be a good time to start going through it.
I would start with removing the carb and give it a thorough cleaning and blow out the jets and all the little passages with compressed air, then do it again.
The accelerator pump thing like Snowflake mentioned should be checked as well, I think it is also called an air-cut valve. They reduce the amount of air that enters the carb to alleviate the lean condition that occurs when you abruptly let off the gas. They can get gooey, and it's #54 in the diagram in the link below;
http://www.motosport.com/atv/oem-parts/suzuki/2004/ltz250/carburetor

Also getting a compression reading isn't a bad idea either.
 
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The quad is 100% stock. I pulled the new plug and it's white on top. I believe it's running lean which would explain it being so hot and the hanging idle and popping. What's causing this though? I checked for an air leak and I don't have one. What could it be?
 
Please help! Give me a list of everything to look for to solve this problem. I've already went through the carb twice and inspected every part while looking at a parts diagram and everything is perfect. Not sure what it could be.
 
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