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My bandit has been running pretty rough recently (Actually, years, but the issue has made the bike unrideable). The bike starts just fine when cold, and I can ride it for about 5 minutes before it starts having power issues. It almost feels like riding a v-twin. I'm 95% sure it's a vacuum leak, and I'm 95% sure it's a vacuum leak through the ISC valve. See the video to see what I'm talking about.
Is the ISC valve supposed to hiss air when the bike is on but the engine is running? I'm certain it's coming through the ISC valve, because if I block the valve with my hand, the hissing noise is quieter, and if I put my ear into the hose that connects the ISC valve to the airbox, it sounds like there is hissing at the end of the hole (but not through the hole). I've taken the assembly as a whole off the throttle body, and replaced the o-rings that connect the hoses of the ISC valve to the throttle body, but the hissing is still there. I believe that there is a leak coming from the ISC valve itself, probably between the o-ring that's in there and sensor body that mounts to the throttle body.
Am I on the right track? Can anyone else with a bandit 1250 confirm whether or not there is supposed to be a hissing noise from the ISC sensor when the bike is just sitting there without the engine running?
Is the ISC valve supposed to hiss air when the bike is on but the engine is running? I'm certain it's coming through the ISC valve, because if I block the valve with my hand, the hissing noise is quieter, and if I put my ear into the hose that connects the ISC valve to the airbox, it sounds like there is hissing at the end of the hole (but not through the hole). I've taken the assembly as a whole off the throttle body, and replaced the o-rings that connect the hoses of the ISC valve to the throttle body, but the hissing is still there. I believe that there is a leak coming from the ISC valve itself, probably between the o-ring that's in there and sensor body that mounts to the throttle body.
Am I on the right track? Can anyone else with a bandit 1250 confirm whether or not there is supposed to be a hissing noise from the ISC sensor when the bike is just sitting there without the engine running?