nodwick
XS650 Member
This weekend- I'll be diving into fixing my xs650. I need anyone's educated input, I have all weekend to wrench I'm just a dude who likes to wrench on bikes sometimes and new to owning an XS.
My Bike:
1981 xs650 (VIN id as "US spec XS-H special 2")
BS34 47.5 pilot 137.5 main
Pods & straight piped
TCI ignition from factory
No other mods (that I can think of/aware of)
Brief background:
I just bought this bike as a non-running incomplete project that is in good condition. Previous owners were about to start cafeing the bike out. They got as far as minimal aesthetic/annoying mods, then engine performance mods (pods and straight pipes) owner grew frustrated and elected to sell it as they had two other bikes that ran well. Before buying I had identified it just needs to be rejetted. Cleaned the carbs and rejetted myself and she's been running great for a about a month Been slowly working out the kinks. (To many to list in this post but some major eye rolls have been had)
4 days prior to issue-removed cheapo baffles from after market mufflers. Because they sounded cheap. And I got tired of it. (Will be doing fully custom exhaust later)
1 day before issue- refueled at same gas station as always. Using E5 from tesco. Every fill up has been from here in my 1.5 months of riding this particular bike (6-7 fillups)
Symptoms below:
intermittent LH side misfiring, and back firing in the exhaust pipe; occurs on accel when engine "8 cycles" on LH cylinder at low rpm
LH cylinder misses intermittently on idle causing stalling. And back fire upon any throttle application. Nearly stranded but was able to use higher than normal RPMs to take off from first
Backfiring on decel, could stem by turning mix screw out to 4-4.5 turns. And also by engaging enrichener to first position.
"Breaking up" on acceleration at all RPM. After period of high rpm, "hard" accelerations, and decelerations symptoms would subside.
Bike acted like this for 1.5 days and after driving it hard the issue subsided. For an entire day. But mix screws were still turned very far out (4.5 turns out) from nominal position (2.5 turns out) did not individually set mixes to compensated levels. Adjusted together for simplicity, but only to compensate for the LH side.
Weekend rolled around and these are my notes and fix actions I took:
[X] Goal: Diag fueling issue/lean condition
[X] Step 1 Clean/Rebuild carbs
• Removal of carbs from the engine revealed a severely kinked fuel line before the T on the right side. Kinked section is permanently deformed and will easily kink off again • Upon inspection of fuel drained from float bowls it's clear crumbling fuel line is the culprit as evident by sizeable black chunks in float bowls (figure 1.1 and 1.2) and kinked fuel line that now has a permanent weak spot.
• Carbs rebuilt and weak spot in fuel line eliminated.
• Kinked spot of fuel line was discolored on the inside and weaker where it had been stressed but I could not easily see any visual degradation.
• Checked spark plugs out of attempting to cover all bases and plugs seemed to be in expected condition. LH plug black, dry and sooty RH nominal plug creme/tan color. (Figure 1.3) To me seemed a secondary effect of having the uneven metering of fuel into the cylinder.
[X]step 2 test ride
• Rides went great, set idle once at operating temp & tweaked carbs to ballpark settings.
• Mix screws turned inwards by .5 turns and engine seems very happy. Not as many nice sounding pops on decel as when it's perfectly dialed in but very slight.
[X] step 3 If mix screws still far out go up pilot jet again
• Un-needed
[ ] If lean condition still exists on full accel at high rpm, up the main jet
• No obvious lean condition from full throttle acceleration but feels like it could be pulling harder. Requires investigation and will monitor during week for insight
Bike parked after 30ish minutes of riding around and tweaking. Feeling accomplished.
With issue seemingly resolved I swapped out spark plug caps for the same model of plug caps (existing ones on the bike were old and crusty. With one having previously un-attach off the wire)
Bike fired up and ran just fine after spark plug caps being swapped.
the next morning
Momentarily started as expected only at 1st notch on the enrichener
then when set to no enrichment after a bit of idling (15-45 seconds) engine totally stalled
Then would not start at normal enrichment setting (1st notch). Had to fully engage enrichener (2nd notch) and then had weak idle. "Solved" by increasing idle screw. Indeterminate amount of time before turning off enrichener. Was immediately suspicious and frustrated but had to get to work
Rode maybe 2-3 miles when the following issues cropped up and grew increasingly until I was left stranded.
LH misses intermittently on idle causing stalling. And back fire upon any throttle application. Making starting from a stop very difficult without stalling.
Backfiring on decel, could lessen by turning mix screws out again to 4-4.5 turns. And also by engaging enrichener to first position.
"Breaking up" on acceleration at all RPM. After period of high rpm, "hard" accelerations, and decelerations resulting in the symptoms subsiding temporarily.
LH cylinder missing at low RPMs causing jerking acceleration and bucking at low speeds.
Bike totally dies (2x before giving up and getting trailered home). Both times before dying all above symptoms occurred. These symptoms also are very similar and I believe to be more than likely the same issue from the previous weeks issues and cleaning the carb relieved the issue for enough time for a test ride and to get a false positive for a fix.
Moments before bike totally died
issues seemed to transition from LH side to both LH and RH. Started as "breaking up" while maintaining speed (sudden uneven power feel without moving throttle) approx 2-3k rpm.dropped down in gears to get engine up in rpm to try and clear the issue as before. I was able to accelerate briefly then after a couple moments it just turned into popping and banging, bike couldn't maintain speed. At low speed felt like someone was switching my key/kill switch on and off repeatedly and then gradually came to a stop with lots of jerking and popping.
This sequence was unchanged both times the bike to decide to totally not fire, with or without enrichener engaged at any position.
---First time bike totally gave up---
Left the bike in parking lot completed an appointment and came back 1.25hrs later. Drained fuel bowls and check for contaminants. LH sample had flecks of black but at very tiny near imperceivable size with 1 larger black fleck and 1 similar sized brownish contaminants (figure 2.1)and RH sample had slightly more black flecks of near imperceivable size and 1 larger black fleck contaminant(figure 2.2) Unable to do any actual fix action. Attempted to fire up bike. It started fine and would idle. but was totally gutless and easy to stall and with misfire on the left side with throttle application until rpms were higher.
Cruising at 30-40 bike would pop and bang and had to keep rpms up. Was trying to limp home.
---Second total stall out---
Symptoms moments before it totally died symptoms were exact same as first time. But difference being it would not fire up again approximately 2hrs later. Would crank strong but no fire, no signs of even trying to start at all. Also I verified fuel is flowing into bowls. But was unable to verify if fuel was entering the cylinders
Many hours later in the evening after a tow, it fired up cold, but left side was intermittent at idle. And idle was low/weak.
My thoughts
I think it's a fuel issue, I want to say the particulates keep clogging the carburetor. But I truthfully don't know. I've never had a run in with dirty or contaminated fuel so this is a first.
What I don't know is what size and concentration of particulate will start to cause issues, obviously the size being anything that will block the little holes in the jets. I have attached photos and would love others opinions because I have mixed feelings if contaminated fuel is what I'm dealing with here.
Since the issue returned after I eliminated the fuel line section that was bad, could this just be left over debris in the lines?
Is there an easy way to inspect a fuel tank with no endoscope/inspection camera? Visibly through the fuel filler hole I can't see anything but really fresh looking metal inside the gas tank.
Could the degradation be from inside the petcocks? My RH petcock Will drip once or twice on my finger when I turn it from "off" to "on" or "reserve"
I've seen that electronic ignition on these bikes, if failing, will usually happen at operational temperatures. but I don't know if that happens on the pamco and other brand aftermarket kits for adapted bikes from points, or if the factory TCI ignition will do the same?
with the jerkiness that happened occasionally I know that's also a symptom of electronic ignition failure?
My bet is still on fuel and I will update as I dig in this weekend. Does anybody have any resources on detailed troubleshooting of a TCI ignition system? I am okay with electronics and will have no problem troubleshooting analog circuits as long as I have a guide in nominal values.
Thanks!
My Bike:
1981 xs650 (VIN id as "US spec XS-H special 2")
BS34 47.5 pilot 137.5 main
Pods & straight piped
TCI ignition from factory
No other mods (that I can think of/aware of)
Brief background:
I just bought this bike as a non-running incomplete project that is in good condition. Previous owners were about to start cafeing the bike out. They got as far as minimal aesthetic/annoying mods, then engine performance mods (pods and straight pipes) owner grew frustrated and elected to sell it as they had two other bikes that ran well. Before buying I had identified it just needs to be rejetted. Cleaned the carbs and rejetted myself and she's been running great for a about a month Been slowly working out the kinks. (To many to list in this post but some major eye rolls have been had)
4 days prior to issue-removed cheapo baffles from after market mufflers. Because they sounded cheap. And I got tired of it. (Will be doing fully custom exhaust later)
1 day before issue- refueled at same gas station as always. Using E5 from tesco. Every fill up has been from here in my 1.5 months of riding this particular bike (6-7 fillups)
Symptoms below:
intermittent LH side misfiring, and back firing in the exhaust pipe; occurs on accel when engine "8 cycles" on LH cylinder at low rpm
LH cylinder misses intermittently on idle causing stalling. And back fire upon any throttle application. Nearly stranded but was able to use higher than normal RPMs to take off from first
Backfiring on decel, could stem by turning mix screw out to 4-4.5 turns. And also by engaging enrichener to first position.
"Breaking up" on acceleration at all RPM. After period of high rpm, "hard" accelerations, and decelerations symptoms would subside.
Bike acted like this for 1.5 days and after driving it hard the issue subsided. For an entire day. But mix screws were still turned very far out (4.5 turns out) from nominal position (2.5 turns out) did not individually set mixes to compensated levels. Adjusted together for simplicity, but only to compensate for the LH side.
Weekend rolled around and these are my notes and fix actions I took:
[X] Goal: Diag fueling issue/lean condition
[X] Step 1 Clean/Rebuild carbs
• Removal of carbs from the engine revealed a severely kinked fuel line before the T on the right side. Kinked section is permanently deformed and will easily kink off again • Upon inspection of fuel drained from float bowls it's clear crumbling fuel line is the culprit as evident by sizeable black chunks in float bowls (figure 1.1 and 1.2) and kinked fuel line that now has a permanent weak spot.
• Carbs rebuilt and weak spot in fuel line eliminated.
• Kinked spot of fuel line was discolored on the inside and weaker where it had been stressed but I could not easily see any visual degradation.
• Checked spark plugs out of attempting to cover all bases and plugs seemed to be in expected condition. LH plug black, dry and sooty RH nominal plug creme/tan color. (Figure 1.3) To me seemed a secondary effect of having the uneven metering of fuel into the cylinder.
[X]step 2 test ride
• Rides went great, set idle once at operating temp & tweaked carbs to ballpark settings.
• Mix screws turned inwards by .5 turns and engine seems very happy. Not as many nice sounding pops on decel as when it's perfectly dialed in but very slight.
[X] step 3 If mix screws still far out go up pilot jet again
• Un-needed
[ ] If lean condition still exists on full accel at high rpm, up the main jet
• No obvious lean condition from full throttle acceleration but feels like it could be pulling harder. Requires investigation and will monitor during week for insight
Bike parked after 30ish minutes of riding around and tweaking. Feeling accomplished.
With issue seemingly resolved I swapped out spark plug caps for the same model of plug caps (existing ones on the bike were old and crusty. With one having previously un-attach off the wire)
Bike fired up and ran just fine after spark plug caps being swapped.
the next morning
Momentarily started as expected only at 1st notch on the enrichener
then when set to no enrichment after a bit of idling (15-45 seconds) engine totally stalled
Then would not start at normal enrichment setting (1st notch). Had to fully engage enrichener (2nd notch) and then had weak idle. "Solved" by increasing idle screw. Indeterminate amount of time before turning off enrichener. Was immediately suspicious and frustrated but had to get to work
Rode maybe 2-3 miles when the following issues cropped up and grew increasingly until I was left stranded.
LH misses intermittently on idle causing stalling. And back fire upon any throttle application. Making starting from a stop very difficult without stalling.
Backfiring on decel, could lessen by turning mix screws out again to 4-4.5 turns. And also by engaging enrichener to first position.
"Breaking up" on acceleration at all RPM. After period of high rpm, "hard" accelerations, and decelerations resulting in the symptoms subsiding temporarily.
LH cylinder missing at low RPMs causing jerking acceleration and bucking at low speeds.
Bike totally dies (2x before giving up and getting trailered home). Both times before dying all above symptoms occurred. These symptoms also are very similar and I believe to be more than likely the same issue from the previous weeks issues and cleaning the carb relieved the issue for enough time for a test ride and to get a false positive for a fix.
Moments before bike totally died
issues seemed to transition from LH side to both LH and RH. Started as "breaking up" while maintaining speed (sudden uneven power feel without moving throttle) approx 2-3k rpm.dropped down in gears to get engine up in rpm to try and clear the issue as before. I was able to accelerate briefly then after a couple moments it just turned into popping and banging, bike couldn't maintain speed. At low speed felt like someone was switching my key/kill switch on and off repeatedly and then gradually came to a stop with lots of jerking and popping.
This sequence was unchanged both times the bike to decide to totally not fire, with or without enrichener engaged at any position.
---First time bike totally gave up---
Left the bike in parking lot completed an appointment and came back 1.25hrs later. Drained fuel bowls and check for contaminants. LH sample had flecks of black but at very tiny near imperceivable size with 1 larger black fleck and 1 similar sized brownish contaminants (figure 2.1)and RH sample had slightly more black flecks of near imperceivable size and 1 larger black fleck contaminant(figure 2.2) Unable to do any actual fix action. Attempted to fire up bike. It started fine and would idle. but was totally gutless and easy to stall and with misfire on the left side with throttle application until rpms were higher.
Cruising at 30-40 bike would pop and bang and had to keep rpms up. Was trying to limp home.
---Second total stall out---
Symptoms moments before it totally died symptoms were exact same as first time. But difference being it would not fire up again approximately 2hrs later. Would crank strong but no fire, no signs of even trying to start at all. Also I verified fuel is flowing into bowls. But was unable to verify if fuel was entering the cylinders
Many hours later in the evening after a tow, it fired up cold, but left side was intermittent at idle. And idle was low/weak.
My thoughts
I think it's a fuel issue, I want to say the particulates keep clogging the carburetor. But I truthfully don't know. I've never had a run in with dirty or contaminated fuel so this is a first.
What I don't know is what size and concentration of particulate will start to cause issues, obviously the size being anything that will block the little holes in the jets. I have attached photos and would love others opinions because I have mixed feelings if contaminated fuel is what I'm dealing with here.
Since the issue returned after I eliminated the fuel line section that was bad, could this just be left over debris in the lines?
Is there an easy way to inspect a fuel tank with no endoscope/inspection camera? Visibly through the fuel filler hole I can't see anything but really fresh looking metal inside the gas tank.
Could the degradation be from inside the petcocks? My RH petcock Will drip once or twice on my finger when I turn it from "off" to "on" or "reserve"
I've seen that electronic ignition on these bikes, if failing, will usually happen at operational temperatures. but I don't know if that happens on the pamco and other brand aftermarket kits for adapted bikes from points, or if the factory TCI ignition will do the same?
with the jerkiness that happened occasionally I know that's also a symptom of electronic ignition failure?
My bet is still on fuel and I will update as I dig in this weekend. Does anybody have any resources on detailed troubleshooting of a TCI ignition system? I am okay with electronics and will have no problem troubleshooting analog circuits as long as I have a guide in nominal values.
Thanks!