Melon
XS650 Member
Hello,
I have an issue that I cannot find a solution to. My 1980 Special starts first kick, has a steady idle and rides fine for ~40 minutes. During the first 25 minutes the idle rises about 2k, which I adjust for with the idle screw while i'm at a stop light. Consistently, around the 40 minute mark, it starts behaving differently. The first signs are a slight jitter in my at-idle RPM seen through the tach, which progresses into noticeable surging as I ride the bike. This happens both at steady throttle and during acceleration. At this point I have 2 minutes of riding until the bike shuts off at the slightest release of throttle. If I let the bike idle in this state, it will stumble intermittently until it finally dies. When I try to kick the bike over again, it turns over about 5 times and makes an aggressive sputtering sound, which almost sounds like its through the carb. I usually let the bike cool off and it starts up first kick, but the previously described symptoms return, proportionately to how long I let it cool off. I have repeated this one three separate days and the same thing happens every time.
Engine:
-Jugs bored and honed with #6 oversized pistons, valves re-seated by a shop
-new cam chain
-Carbs are BS34's with #45 pilots and #140 mains, float level set at 27mm, fuel screws at 3 turns out, new boots and gaskets, Uni pod filters, boot barbs capped with rubber stoppers
-New gas cap, and replaced the vacuum petcock with a old style on/off ball valve petcock
-Compression after a few kicks (cold) is ~150psi on both cylinders
Electrical:
-new wiring harness from Mikesxs
-PMA kit https://www.mikesxs.net/yamaha-xs650-xscharge-permanent-magnet-alternator-kit-pma-200-watt.html
-Battery removed and replaced with capacitor
-TCI replaced with e-advanced https://www.mikesxs.net/blog/how-to...-xs650-gen-ii-e-advancer-electronic-ignition/
-new ignition coil https://www.mikesxs.net/yamaha-xs650-ultimate-high-output-coil.html
I tested the coil after the bike died and it reads 2.4ohms//16.8kohms. When cold it reads 2.5//13kohms. The webpage gives the specs as "Primary resistance 2.45 ohms. Secondary resistance 15k ohms" so these values seem in the ballpark.
As you can see ive invested a lot into this bike, and have done a decent amount of research. but I am totally stumped on this one. My first thought was the coil, but it still seems to have spark when kicked after dying, as it sputters for a bit.
Any ideas?
I have an issue that I cannot find a solution to. My 1980 Special starts first kick, has a steady idle and rides fine for ~40 minutes. During the first 25 minutes the idle rises about 2k, which I adjust for with the idle screw while i'm at a stop light. Consistently, around the 40 minute mark, it starts behaving differently. The first signs are a slight jitter in my at-idle RPM seen through the tach, which progresses into noticeable surging as I ride the bike. This happens both at steady throttle and during acceleration. At this point I have 2 minutes of riding until the bike shuts off at the slightest release of throttle. If I let the bike idle in this state, it will stumble intermittently until it finally dies. When I try to kick the bike over again, it turns over about 5 times and makes an aggressive sputtering sound, which almost sounds like its through the carb. I usually let the bike cool off and it starts up first kick, but the previously described symptoms return, proportionately to how long I let it cool off. I have repeated this one three separate days and the same thing happens every time.
Engine:
-Jugs bored and honed with #6 oversized pistons, valves re-seated by a shop
-new cam chain
-Carbs are BS34's with #45 pilots and #140 mains, float level set at 27mm, fuel screws at 3 turns out, new boots and gaskets, Uni pod filters, boot barbs capped with rubber stoppers
-New gas cap, and replaced the vacuum petcock with a old style on/off ball valve petcock
-Compression after a few kicks (cold) is ~150psi on both cylinders
Electrical:
-new wiring harness from Mikesxs
-PMA kit https://www.mikesxs.net/yamaha-xs650-xscharge-permanent-magnet-alternator-kit-pma-200-watt.html
-Battery removed and replaced with capacitor
-TCI replaced with e-advanced https://www.mikesxs.net/blog/how-to...-xs650-gen-ii-e-advancer-electronic-ignition/
-new ignition coil https://www.mikesxs.net/yamaha-xs650-ultimate-high-output-coil.html
I tested the coil after the bike died and it reads 2.4ohms//16.8kohms. When cold it reads 2.5//13kohms. The webpage gives the specs as "Primary resistance 2.45 ohms. Secondary resistance 15k ohms" so these values seem in the ballpark.
As you can see ive invested a lot into this bike, and have done a decent amount of research. but I am totally stumped on this one. My first thought was the coil, but it still seems to have spark when kicked after dying, as it sputters for a bit.
Any ideas?
