First, let me say I did read existing threads, but I think my problem may be a little different. I have a 2001 ST1100 CA model with ABS and all the PAIR plumbing. It only has 8000 miles. I recently took it into a shop with a fuel leak. After much effort, we found that one carb was leaking fuel out the bottom. This was fixed by shop with a new gasket (and a ton of cash from my pocket). Leak is definitely eliminated.
Here is the problem. Since the Carbs were re-installed and synched by dealer (after fixing the fuel leak), I have a NEW problem in cold running. In the morning, when cold, the bike will back-fire up through the carbs into the airbox. This causes a loud "POCK - POCK" sound and (with tank cover removed), I can see the vent hoses coming from the airbox pulse and shake. It may do this 20-30 times in a half-mile of riding.
As before, the bike would start right up with full choke. I let it run at 2200 rpm high idle on full choke for about 40 seconds, then back to half-choke. Before the "fix" the bike would run smoothly on half-choke for about 1 mile, then I would thumb off the choke, when the bike was fully warmed.
Now, even after long warm-up, when I try to ride off, the engine will back-fire (if that is the right term) into the air box for a couple miles before the engine is fully warm. It will do this at all choke settings from half-choke to just barely on. (It does not back-fire during the fast idle with full choke).
The bike otherwise runs fine when fully warm. Throttle response is good, acceleration is good, no backfiring through the exhaust pipes, even on deceleration.
Q: What can I do to eliminate the back-firing into the airbox? I assume this is not a good thing and could potentially cause some issues with fouling or airbox seals. I'm reluctant to take it back to the same dealer because they seem to create a new problem every time they worked on it and it took a half-dozen carb-off/carb-on sequences over a month to fix the fuel leak.
NOTE: The carbs were supposedly synched properly. The carbs were also thoroughly cleaned not too long ago. After cleaning this popping did not occur. The problem arose after fuel leak fix. Plugs were pulled and look fine. This is something new, post-"fix".
Here is the problem. Since the Carbs were re-installed and synched by dealer (after fixing the fuel leak), I have a NEW problem in cold running. In the morning, when cold, the bike will back-fire up through the carbs into the airbox. This causes a loud "POCK - POCK" sound and (with tank cover removed), I can see the vent hoses coming from the airbox pulse and shake. It may do this 20-30 times in a half-mile of riding.
As before, the bike would start right up with full choke. I let it run at 2200 rpm high idle on full choke for about 40 seconds, then back to half-choke. Before the "fix" the bike would run smoothly on half-choke for about 1 mile, then I would thumb off the choke, when the bike was fully warmed.
Now, even after long warm-up, when I try to ride off, the engine will back-fire (if that is the right term) into the air box for a couple miles before the engine is fully warm. It will do this at all choke settings from half-choke to just barely on. (It does not back-fire during the fast idle with full choke).
The bike otherwise runs fine when fully warm. Throttle response is good, acceleration is good, no backfiring through the exhaust pipes, even on deceleration.
Q: What can I do to eliminate the back-firing into the airbox? I assume this is not a good thing and could potentially cause some issues with fouling or airbox seals. I'm reluctant to take it back to the same dealer because they seem to create a new problem every time they worked on it and it took a half-dozen carb-off/carb-on sequences over a month to fix the fuel leak.
NOTE: The carbs were supposedly synched properly. The carbs were also thoroughly cleaned not too long ago. After cleaning this popping did not occur. The problem arose after fuel leak fix. Plugs were pulled and look fine. This is something new, post-"fix".
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