Posted by Fats on January 24, 2000 at 18:37:48:
I have just reviewed all our references in the forum to backfiring. I wish I had a better technical understanding of what is going on to cause this. I accept that the solution with the white spacer works but I wonder if there isn't an equally simple couple of riding practices which will also work just as well.
First some background on my riding patterns. My Savage is kept in the country - about 20 miles from town. Obviously it gets lots of highway runs - at the speed limits. When I bought my Savage last May - it is an '88- there was lots of backfiring. As the highway miles started to build up the backfiring slowly disappeared.
I can identify two possible reasons for the disappearance seem to emerge.
1. Backfiring is caused by a carbon build up creating a hot spot which will ignite the un-burned gasses racing through the exhaust pipe. With longer and higher rpm runs provided by gettint out onto the highway, these carbon buildups over time themselves were burnt away. Once they were gone there was no source of ignition and the backfiring started to disappear,
2. When I first got the machine - I had a habit of only partially rolling the throttle off when decelerating. Even with the throttle rolled back fuel is still being pulled through the engine in excess of the requirements and exploding in the exhaust system. By modifying my riding habits - now the throttle when it is rolled off is rolled all the way off - less fuel is drawn through and again less backfiring occurs.
I also am a great believer in the $3.50 tune up - a new spark plug. A clean new plug helps the motor start easier and run cooler than one with the incorrect gap and the electrodes eaten away and possibly slightly fouled around the porcelin insulator with carbon (another potential ignition spot leading to backfiring)
My Savage still occassionally lets me know it is there - setting up for a corner on the highway and occassionally "whuffing" when shutting it off - but there is far less banging and popping than there was initially.
I would be interested in hearing if any other forum posters have seen similar patterns and have use similar strategies to solve the backfiring trait of our big singles.
I don't object to the backfiring but it does cause some rather interesting pressures inside the exhaust sytem - all the way back to the valves which may not be the best for our rides.
Keep the rubber side down
Fats