Muffler Smokes

[primerbulb120]

I have a Craftsman 25cc blower. When I run this blower at full throttle for 30 seconds and then turn it off, hot white smoke pours off and out of the muffler for about 10 seconds. The smoke rises off the metal of the muffler and some comes out the exhaust hole. When I remove the spark arrestor, there is less smoke but the problem is still there. When I remove the muffler altogether, there is no smoke. Could there be oil in the muffler that is being heated by the exhaust? When I take the muffler off, I notice that the exhaust port is oily. I have had several machines do this in the past and am looking for an explanation.
I have five questions:

1. What causes the problem?
2. What should I do to stop it?
3. Will the problem go away if I simply continue to use the blower?
4. Is it safe to use the blower while the problem persists?
5. While the problem persists, is there any risk of the blower catching on fire while I am using it or after I have shut it down?

I want to blow off my driveway, but I am afraid to use my blower for fear it will catch on fire in the process.

Thanks!

 

[Flintmotorsports]

so it sounds like the unit is not getting the proper fuel mixture so check you fuel mixture
and make sure there is no water in your gas that is causing it to smoke.

 

[primerbulb120]

The engine hardly smokes at all while running, but it is after I turn it off that the smoke pours out. I should say off, not out, because it arises off the metal of the muffler. While the muffler is supposed to be bright and shiny, the areas from which the smoke arises are a dull grey.

 

[Flintmotorsports]

how long has it been doing this? is the unit old or new?

 

[primerbulb120]

The unit has "2008" on the EPA label. It was given to me broken, and I have just fixed it. The person from whom I got it did not say anything about it smoking. When I got it, it refused to start because of a clogged fuel system. I replaced all the components of the fuel system except the body of the gas tank, plus the spark plug. It has smoked since I fixed it.