My GS550E is stalling unpredictably.

[Guest]

It seems like 10-15% of the time, when stopping at an intersection, my bike will stall. The revs will just drop to zero, like it's not getting fuel, unless I baby the throttle. Even then, it runs rough. It will usually start right back up and run fine after this happens.

Most of the time the bike runs predictably. The mixture screws[edit] are not dialed in perfect, and the bike idles a little high, but this is consistent. Still, stalling 10% of the times I come to a stop is unacceptable.

I strongly suspect there's something wrong with the vacuum petcock, but I want to confirm or disprove this before I drop $80 on a new one.

Any ideas?

[cowboyup3371]

Sounds like you are running lean - have you checked the intake boots and were the orings replaced?

[tkent02]

Any ideas?

Test the petcock.

[Ira]

Sounds like you are running lean - have you checked the intake boots and were the orings replaced?

I have not replaced the o-rings, and I need to do this. The plugs do not look lean (a little dark if anything), but I haven't got the mixture screws dialed in either so this could be the case.

[Ira]

Test the petcock.

the petcock works, in that fuel comes out when there is vacuum. I have transparent tygon lines, so I can see fuel in the lines when the bike is running. I'm concerned it's not getting enough to keep the bowls full. Is this possible?

[tkent02]

Test it, see how much flows into a bucket or something when vacuum is aplied to the vacuum line. It doesn't sound likely to be the problem while idling, as before it has to idle you usually slow down, an neither idling or slowing down uses much fuel compared to cruising along or accelerating.

I woud guess cowboyup is on the right page, it's lean from some reason, but I'd also guess you need to do a whole bunch of things, everything from adjusting the valves to synching the carbs, probably most of the routine maintenance has not been routinely done.

[Ira]

Test it, see how much flows into a bucket or something when vacuum is aplied to the vacuum line. It doesn't sound likely to be the problem while idling, as before it has to idle you usually slow down, an neither idling or slowing down uses much fuel compared to cruising along or accelerating.

I woud guess cowboyup is on the right page, it's lean from some reason, but I'd also guess you need to do a whole bunch of things, everything from adjusting the valves to synching the carbs, probably most of the routine maintenance has not been routinely done.

i adjusted the valves in the last couple months, so they are definitely in spec. the carbs are bench synced only.

the plugs are new, the coils test ok, and the timing is set, so i'm pretty sure this is a fuel/air problem.

sounds like next steps are;

- replace the o-rings on the intake boots
- do a vacuum sync
- adjust mixture screws
- anything else?

[tkent02]

Whie you have the carbs off to do the O rings, I would definitely clean the carburetors.

[Ira]

Whie you have the carbs off to do the O rings, I would definitely clean the carburetors.

they are clean and rebuilt with new jets, o-rings and gaskets.

[cowboyup3371]

Why new jets? Did you buy a "rebuild kit"? If so, put your stock jets back in, unless you have a different pipe or running pods, as those in the rebuild kits are crap based on what most have found out.

[Ira]

Why new jets? Did you buy a "rebuild kit"? If so, put your stock jets back in, unless you have a different pipe or running pods, as those in the rebuild kits are crap based on what most have found out.

i have a stage 3 dynojet kit and k&n pods. i understand this changes a lot of things, but i was able to tune the carbs for good response at all throttle positions. my idle was lean with the pods, so it is sized up to 45 with mikuni branded jets.

[cowboyup3371]

It would have been nice to know that stuff from the beginning so the right people could have maybe spoke up.

I still recommend changing out the orings and getting a synch done but I'm clueless when it comes to jetting and pods. That's only because mine is still stock (airbox, pipes, and jets) so I'll keep watch from the sidelines.

[Ira]

sorry for the confusion! like i said, 90% of the time, the bike runs great. good throttle response, predictable idle, etc. then, out of nowhere, i'll come to a stop and it dies.

if i had to correlate it with something, i'd say it does this most right after the bike warms up. like on short, mile or so trips around town. i don't know if that has anything to do with it though, because the bike is new to me and most of my riding is around town.

[tkent02]

Are you sure the throttle is closing to stop on the idle speed screw and not on throttle cable tension only? Because if the cable is stopping the throttle it won't always close to exactly the same spot, especially if the cable is old.

You have plenty of slack in the throttle cable so the throttle mechanism closes until it hits the screw? You should hear a good solid "Clack" when you close the throttle?

[Ira]

I checked the throttle stop yesterday (the cable has slack) and pulled the petcock.

The petcock seems ok, in that the vacuum valve works. I checked all of the passages with carb cleaner.

At this point, I have to imagine there's a significant air leak somewhere. A vacuum sync should confirm this, right?