choppinlefty
XS650 Member
Hi there folks. Thanks in advance for hearing this one out. I've got a 1979 xs650 that I bought a few years ago. Since day one, the right hand cylinder has given me varying degrees of problems. But I'll describe the current one. As it stands, the bike is a one-two kick startup but at first it pretty much only runs on the left cylinder until it warms up. Reving it a bit will get the right hand cylinder to fire intermittently but not consistently, and with lots of backfiring on decel. Once the bike is warm, the right hand cylinder will fire fine, though it seems like I don't have great power (I keep up with traffic fine, but it just seems sluggish to me) and again, tons of backfiring on decel.
I've got stock carbs on, though I'm running an aftermarket tank without the vacuum petcock, so the carb boots are sans vacuum barbs. The left cylinder is 2.5 turns out on the mix screw, the right I've been fiddling with a lot thinking its a lean condition, but its like 3.5 turns out now. Helps with the backfiring, but seems like way too much difference, and again, still crummy startup. Recently completely rebuilt the carbs twice, full soak and rinse and blown out with an aircan. Pretty sure all my passages are clear.
At the moment I'm only running stock headers, no mufflers (I had an exhaust I built on it earlier, but it leaked too much and just threw the headers on to run it. The other exhaust had the same problems) I am saving to get a decent set of pipes but the prices have gone up a lot from what I remember, so not happening right away. New gaskets at the heads.
As near as I can tell with the skills I have, the timing is correct, valve spacing is correct and I bench synced the carbs but do not own a manometer(?) so no precision tuning there. Cam chain tension was also correct last I checked. Like I said, seems no matter what I do, the RH side has a problem that I cannot figure out. Any help as to whats going on here would be greatly appreciated.
I've got stock carbs on, though I'm running an aftermarket tank without the vacuum petcock, so the carb boots are sans vacuum barbs. The left cylinder is 2.5 turns out on the mix screw, the right I've been fiddling with a lot thinking its a lean condition, but its like 3.5 turns out now. Helps with the backfiring, but seems like way too much difference, and again, still crummy startup. Recently completely rebuilt the carbs twice, full soak and rinse and blown out with an aircan. Pretty sure all my passages are clear.
At the moment I'm only running stock headers, no mufflers (I had an exhaust I built on it earlier, but it leaked too much and just threw the headers on to run it. The other exhaust had the same problems) I am saving to get a decent set of pipes but the prices have gone up a lot from what I remember, so not happening right away. New gaskets at the heads.
As near as I can tell with the skills I have, the timing is correct, valve spacing is correct and I bench synced the carbs but do not own a manometer(?) so no precision tuning there. Cam chain tension was also correct last I checked. Like I said, seems no matter what I do, the RH side has a problem that I cannot figure out. Any help as to whats going on here would be greatly appreciated.
I did just do a rebuild on the motor so i'd better have good compression 
but i'll check what it is and let you know.
and when looked over the carbs again, i realized how much i'd messed with the settings before rebuilding the motor. once i matched the butterfly's (that were unintentionally misaligned) and set mixture screws back to normal it ran just okay. it still took some higher idle to get the left cylinder to start firing so i'll check that pilot circuit closer. my main issue now is that it's running lean and it's no surprise since i have stock jet sizing but modified exhaust and pod filters. time to do more reading on carb settings
