I've been working on my 300 for some time. Bought it on a limited budget and finally have it starting and running. However, after running about 3-5 minutes, it accelerates to the moon and i have to shut it down. I've had the carb apart and it is clean now. Gasket on the bottom half has been replaced. Any ideas what may be causing this? Any help would be greatly appreciated.

 

i'm presuming the slide is in correctly seeing how it idles 3-5 mins, SO, with that in mind, it sounds like once things warm up, a vacuum leak appears. hmmm...wonder where it would show up? . have you checked the intake boot? does it have an O-Ring with a flange on the boot? is it facing the right way? i'm just thinking out loud here cause i haven't seen this problems before. maybe some others have.

 

Thank you for the ideas. I'll be working on it again and will be checking on these. Thanks again.