1996 XP fuel/oil problem

[go_panthers]

I have a friend with a '96 XP. We rebuilt the carbs last year, and cleaned them about a month ago. Here is the symptoms as he describes them:

When I first start it will run for 100 yards or so, then its like I turn off the gas. But it comes down to a little over idle and it sounds like its missing or something. But its smoking really bad. I can pull out the choke and it dies but starts right back up and goes for another 100 yards or so. If I just let off the gas it will idle just fine. If I kill by the kill switch is still has the issue when I start it back up. It evidentially quits this and will run fine - even all the way to the other end of the lake but as soon as* I kill the engine it starts over again.
When I looked at the plugs they are really black so I m thinking too much oil and not enough gas.

Is this an obvious set of symptoms to anyone? Just wanted to check before we start troubleshooting.