G
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I know there's a post just like it next to mine, and a dozen or more in the search results. I've read them, and know popping on decel likely indicates either a lean condition or an exhaust leak. But different bikes may have different problems, so I figure it can't hurt to ask.
80 GS1000G, all stock, airbox, factory jets etc, original exhaust with no obvious leaks. Valves adjusted, carbs clean and unblocked, new orings and rubber, and I've done everything I can to eliminate air leaks (full list of work below). Carbs are synced with Carbtune pro. Pilot screws are 3 1/2 turns out on #s 1&4, and about 3 turns on 2&3. With the BS carbs it's really tough to fine-tune by ear, but my plugs had hinted that the outside cylinders may have been leaner, so I turned them out "all the way" to 3.5 to see if it eliminated the popping (it didn't). I didn't go any farther than that based on what I've read here. Plugs are now a uniform lightish tan (pic below), though I haven't done a proper chop test yet.
The bike starts up with about half choke, no backfiring, and settles down within a minute or two, and I can ride off with little or no choke. Lots of power all the way through the rev range. Holds idle, and returns to idle quickly and consistently. Idle is set to a hair under 1000. Exhaust is a little light gray when warming up, which I assume is just moisture as it's gone after I've ridden it.
Along with fairly consistent popping when I let off throttle (not very loud, but obvious), there's a very minor repetitive popping (almost like a "burbling") when holding a cruising speed. I don't see fluctuation on the tach needle, but I can kind of feel it in the movement in the bike, almost like a subtle rocking movement forward and back, like there's a repeating hesitation or maybe a misfire. It's that rhythmic pattern that has me wondering. Does that sound like it's running lean? Or could it be a float / fuel level issue, something to do with fuel sloshing around? Could that point me at something that I've missed?
The exhaust is stock, no obvious holes, but a rattle on the right side tells me it has internal problems. I've already bought a set of exhaust seals, but don't plan to install them until the winter (because I'm sure to shear some bolts and don't want to lose any more riding time this season). I don't want to replace the exhaust if I can avoid it.
Here's everything I've done: adjusted the valves, full carb teardown and cleanup (twice) following the instructions on Basscliff's site, replaced all o-rings, and basically all of the fuel system rubber (boots, intake pipes, fuel and air lines). New petcock (2 years old). Adjusted floats with a micrometer: PO had measured them to the top ridge, I readjusted them correctly, which moved them "up" (so, on the bike, they're lower), though I haven't directly measured fuel levels yet. Float springs seemed fine, the valve held the floats in position. Resealed the airbox twice (had some leaking after the first time, redid the job with additional tape and some silicone). Spray test doesn't show any obvious air leaks, but I know that's not a perfect test. New Uni filter, oiled per the instructions. New plugs, gapped to spec, with recent plug terminals, new battery. Electrical system is stock, charging seems fine (but haven't done any electrical tests yet).
What have I missed?
Thanks,
Chris
80 GS1000G, all stock, airbox, factory jets etc, original exhaust with no obvious leaks. Valves adjusted, carbs clean and unblocked, new orings and rubber, and I've done everything I can to eliminate air leaks (full list of work below). Carbs are synced with Carbtune pro. Pilot screws are 3 1/2 turns out on #s 1&4, and about 3 turns on 2&3. With the BS carbs it's really tough to fine-tune by ear, but my plugs had hinted that the outside cylinders may have been leaner, so I turned them out "all the way" to 3.5 to see if it eliminated the popping (it didn't). I didn't go any farther than that based on what I've read here. Plugs are now a uniform lightish tan (pic below), though I haven't done a proper chop test yet.
The bike starts up with about half choke, no backfiring, and settles down within a minute or two, and I can ride off with little or no choke. Lots of power all the way through the rev range. Holds idle, and returns to idle quickly and consistently. Idle is set to a hair under 1000. Exhaust is a little light gray when warming up, which I assume is just moisture as it's gone after I've ridden it.
Along with fairly consistent popping when I let off throttle (not very loud, but obvious), there's a very minor repetitive popping (almost like a "burbling") when holding a cruising speed. I don't see fluctuation on the tach needle, but I can kind of feel it in the movement in the bike, almost like a subtle rocking movement forward and back, like there's a repeating hesitation or maybe a misfire. It's that rhythmic pattern that has me wondering. Does that sound like it's running lean? Or could it be a float / fuel level issue, something to do with fuel sloshing around? Could that point me at something that I've missed?
The exhaust is stock, no obvious holes, but a rattle on the right side tells me it has internal problems. I've already bought a set of exhaust seals, but don't plan to install them until the winter (because I'm sure to shear some bolts and don't want to lose any more riding time this season). I don't want to replace the exhaust if I can avoid it.
Here's everything I've done: adjusted the valves, full carb teardown and cleanup (twice) following the instructions on Basscliff's site, replaced all o-rings, and basically all of the fuel system rubber (boots, intake pipes, fuel and air lines). New petcock (2 years old). Adjusted floats with a micrometer: PO had measured them to the top ridge, I readjusted them correctly, which moved them "up" (so, on the bike, they're lower), though I haven't directly measured fuel levels yet. Float springs seemed fine, the valve held the floats in position. Resealed the airbox twice (had some leaking after the first time, redid the job with additional tape and some silicone). Spray test doesn't show any obvious air leaks, but I know that's not a perfect test. New Uni filter, oiled per the instructions. New plugs, gapped to spec, with recent plug terminals, new battery. Electrical system is stock, charging seems fine (but haven't done any electrical tests yet).
What have I missed?
Thanks,
Chris
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