Hey Folks!
My wife's brother passed away suddenly back in December, and as part of the settlement of his small estate, she inherited the 1980 XS650 shown in the picture below. I've done little to it so far other than giving it new oil & filter, new air filters, new plugs, bleeding the brakes, installing the turn signals (for some reason, my brother-in-law had them in a box in his garage), and putting on a new front tire (the old one had a slow leak around the bead). Generally speaking the bike runs well, except that it seems to back fire occasionally from the left cylinder.
While idling, I occasionally feel a small gust of air emit from the nipple used for doing a vacuum balance between the two carbs (which I haven't done). This also happens in concert with the louder "POP" coming from the exhaust. Even more frightening is that I occasionally see a small "spark" exit from it (the nipple, not the exhaust!) which makes me think the intake valve isn't fully closed when the plug fires. By the way, there's a rubber cap and clamp on the right-side nipple, but it's missing on the left.
While checking the idle with my inductive pickup meter, I noticed that I got an unsteady measurement when connected to the left sparkplug lead, but a good solid measurement on the right.
Now, oddly enough, when I checked the timing using my inductive timing light attached to the left sparkplug lead, the mark appeared to be solidly on the 15 degree BTDC mark.
I have not adjusted the cam tensioner nor any of the valve clearances yet.
Any suggestions on where to start my troubleshooting?
Thanks!
Dave
Gambrills, MD
1980 Yamaha XS650SG
1993 Harley Davidson Ultra Classic
2000 Harley Davidson Low Rider
2012 Harley Davidson Sportster 883 Super Low
2015 Harley Davidson Heritage Classic
2021 Can-Am F3 Special
My wife's brother passed away suddenly back in December, and as part of the settlement of his small estate, she inherited the 1980 XS650 shown in the picture below. I've done little to it so far other than giving it new oil & filter, new air filters, new plugs, bleeding the brakes, installing the turn signals (for some reason, my brother-in-law had them in a box in his garage), and putting on a new front tire (the old one had a slow leak around the bead). Generally speaking the bike runs well, except that it seems to back fire occasionally from the left cylinder.
While idling, I occasionally feel a small gust of air emit from the nipple used for doing a vacuum balance between the two carbs (which I haven't done). This also happens in concert with the louder "POP" coming from the exhaust. Even more frightening is that I occasionally see a small "spark" exit from it (the nipple, not the exhaust!) which makes me think the intake valve isn't fully closed when the plug fires. By the way, there's a rubber cap and clamp on the right-side nipple, but it's missing on the left.
While checking the idle with my inductive pickup meter, I noticed that I got an unsteady measurement when connected to the left sparkplug lead, but a good solid measurement on the right.
Now, oddly enough, when I checked the timing using my inductive timing light attached to the left sparkplug lead, the mark appeared to be solidly on the 15 degree BTDC mark.
I have not adjusted the cam tensioner nor any of the valve clearances yet.
Any suggestions on where to start my troubleshooting?
Thanks!
Dave
Gambrills, MD
1980 Yamaha XS650SG
1993 Harley Davidson Ultra Classic
2000 Harley Davidson Low Rider
2012 Harley Davidson Sportster 883 Super Low
2015 Harley Davidson Heritage Classic
2021 Can-Am F3 Special