Engine Sputter, Marbles, and Other Ramblings
I have found so much helpful information on this site that I wanted to give a little something back: I have had intermittent problems with the infamous "engine sputter." The symptoms are riding along around 60 mph when it suddenly feels like one or both cylinders become starved for fuel. Opening the throttle does nothing. After a short time (maybe 30 seconds; it's hard to know under the circumstances), the engine suddenly comes back as if nothing had happened.
After checking every suggestion I could find on the forum, I ended up replacing the short vacuum hose that runs from the carb port to the fuel shutoff. The vacuum hose that was on there had probably been there for 17 years. It was stiff and not flexible at all. I replaced it with a softer, much more flexible piece of vacuum hose and haven't had a problem since. I've ridden under the same conditions (the same stretch of road, same speed, same amount of fuel remaining in the tank - everything I could reproduce) and I haven't had a problem since.
Did this solve my problem? I think so, but the engine sputter problem seems so unpredictable and so unexplainable, who knows? But it has been good so far.
Now about marbles: I had seen all the posts about marbling but never tried it. I was doing some cleaning around the house and ran across two marbles and guess what I thought of... Oh my gosh! Is it my imagination; wishful thinking, or does this thing run noticeably better? Not only is the backfiring gone, but I'm convinced that it performs better. And it was so easy to do, I don't know why I didn't do it before. The glass marbles were exactly the right size and seem to work perfectly. And it is totally reversible, if you ever needed to undo it.
To everyone who participates in the forum: thanks for all the great information.