rfvallejo wrote on 12/31/69 at 16:00:05:Just changed the pipe. I heard re-jeting will be much more gas consuming.
Well then you only made the stock lean condition even worse. I'm surprised it didn't run like crap. It almost certainly ran hotter. When you open up the exhaust, you increase the airflow (at least until you reach another bottleneck, like the air filter), which makes it horribly lean. The stock mixture actually has too much air (or too little fuel) in its fuel/air mixture. When you add more air by changing the exhaust, you MUST add more fuel. That is accomplished in various places: pilot circuit (air mixture screw and pilot jet), main jet, and the needle position (white spacer). There are a lot of posts on this topic and you really should read quite a few before just swapping mufflers.