LeftyKash
XS650 Enthusiast
My 81XS650 SH has an intermittent problem that is giving me fits! Every few miles (like 4-10mi) the bike will stop running. Usually I'm on the highway, cruising along in 5th @ 4-5K rpm. Often it backfires 1x upon stopping. If I pull in the clutch and coast along for 10-15 seconds, I can usually drop the clutch and it starts back up. It's never happened at idle or when just riding on surface streets, but most of my miles are highway so ¯\_(ツ)_/¯ Also, when the bike dies, the electric seems to keep going. The gauges stay lit and the headlight stays on.
Here's some background:
I bought this bike about a month ago, it's a very clean 81 XS650. When I bought it, it wouldn't run off of Choke. I cleaned the carbs (but didn't mess with the floats or the float valve.) Honestly, they we're pretty much sparkling clean. I also found that the left intake manifold barb was all leaky and barely in place, so I replaced both intake manifolds. While I was at it, I replaced the spark plugs. Once I put everything back together the bike started right up! I sprayed around with carb cleaner and couldn't find any leaks. Now it idles and runs fine, except for the aforementioned problems.
I thought it was likely a fuel delivery issue, so I cleaned the tank vent and replaced the filter with a piece of scotch brite. I also replaced the sealing gasket. The issue was still present afterwards. Then I tried just leaving the tank open to confirm that it wasn't the vent. Still no good.
Then I thought maybe it was the vacuum petcock. It seems like most of the failure modes were with the petcock leaking, but I wasn't sure. I bought a non vacuum replacement of amazon. It bolted right up, but honestly, it's a piece of crap. The fuel line barb is 3/16 instead of 1/4 and the right angle barb was just a press fit that leaked. I brazed it, and made the 3/16 fuel line fit to the inline filter that I installed.
I used a clear filter and replacement line, and I can see gas flowing through it, although the line doesn't seem to 'fill up'. Looks like there's always air in there. Anyways, I started the bike up and hit the highway. Same thing happened again. If anything it was a bit more frequent. Now I'm not sure what else to check or look at. Any ideas?
Thanks!
Here's some background:
I bought this bike about a month ago, it's a very clean 81 XS650. When I bought it, it wouldn't run off of Choke. I cleaned the carbs (but didn't mess with the floats or the float valve.) Honestly, they we're pretty much sparkling clean. I also found that the left intake manifold barb was all leaky and barely in place, so I replaced both intake manifolds. While I was at it, I replaced the spark plugs. Once I put everything back together the bike started right up! I sprayed around with carb cleaner and couldn't find any leaks. Now it idles and runs fine, except for the aforementioned problems.
I thought it was likely a fuel delivery issue, so I cleaned the tank vent and replaced the filter with a piece of scotch brite. I also replaced the sealing gasket. The issue was still present afterwards. Then I tried just leaving the tank open to confirm that it wasn't the vent. Still no good.
Then I thought maybe it was the vacuum petcock. It seems like most of the failure modes were with the petcock leaking, but I wasn't sure. I bought a non vacuum replacement of amazon. It bolted right up, but honestly, it's a piece of crap. The fuel line barb is 3/16 instead of 1/4 and the right angle barb was just a press fit that leaked. I brazed it, and made the 3/16 fuel line fit to the inline filter that I installed.
I used a clear filter and replacement line, and I can see gas flowing through it, although the line doesn't seem to 'fill up'. Looks like there's always air in there. Anyways, I started the bike up and hit the highway. Same thing happened again. If anything it was a bit more frequent. Now I'm not sure what else to check or look at. Any ideas?
Thanks!
Last edited: