Backfiring, pipe glowing

I just picked up an 04 RMZ 250. Had no packing in the silencer. Rode it sunday for
about 4 hrs with no problems aside from running rough at low speed and wouldn't idle. I repacked the silencer and checked the pilot jet to make sure it wasn't plugged. Everything clean and back together. Now it Backfires and blows flames and the head pipe starts glowing within 1/2 a minute running in the garage.
Intake boot not leaking, Checked it.
Any ideas?
Thanks
Bruce  

Might have packed it wrong or there is a air leak somewhere.  
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I love this dirt stuff.

try and keep things in one thread!  
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Gittin ur dun on me Ski-Bear in
Paris, Ontario
Ford F150
Yamaha Phazer
Honda crf230

I feel more important than a dwarf among midgets.

Didn't see the other one at first.  
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I love this dirt stuff.

Sounds like something went wrong with the packing...although a dirt bike blowing flames does sound pretty cool   though i would not want that to happen to mine..I would take out the packing and see if something is visibly wrong with the silencer packing  

Sounds to me like it leaning out. Maybee because of the packing but if the bike has been sitting the idle jet could be cloggged
Tim  

Back fire means fires backwards or makes a noise in the induction side of an engine

After fire is an explosion in the exhaust side

a back fire is caused by a slower burn of a mixture that is too lean.

An after fire is caused by combustion taking place in the exhaust.
Sorry to get all that vocab on you.

Now it ran fine, you "fixed" and it now does not run as fine...check your math. Take a good hard look at what you did. Is the new packing blocking the exhaust? is the part correctly installed.

Hint, when you are double checking your work, assume nothing. Start from bolt no. 1 and check every thing you touched, Beleve me if something can be screwed up, I probably have done it my self. I just try to learn each time.  
bald as a bean..old as your dad..but rides like a fool

try the air screw at the bottom of your carb. i put a longer aftermarket one on my crf when i change my pipes arround or diff weather conditions. its only a 20$$ part and i wont ever go without one on a 4 stroke.