Stutter at Idle, not full power in 1st gear either

[taochaos]

Hello, this is my first post. Love the site, so much info! I just bought a 1983 GS1100e, it's a great bike.

So I am having a problem here. I get a stutter at idle and I can't seem to figure it out. Here's what I have done so far:
Compression test - low, but within specs
Valve adjustment - some of the valves were stuck shut
Carb sync - couldn't get it right, the bike has a 4 into one Kerker pipe and a uni filter. this makes me think the bike's carbs may be jetted too, but haven't taken them apart to find out. Finally got it to stop backfiring by turning the air pilot screws out like 6 FULL turns. This seems crazy, but it's running better. I haven't yet checked the plugs to see if it's too lean. I also had to turn the middle sync screw all the way out to sync the carbs - it still doesn't seem that great.

Although the stutter is much improved, it still is there when idling when cold. I was told the carbs were recently cleaned by the guy I bought it from, but I am thinking of dipping them or something. If I open them up I can also least see if they are jetted and how much.

Any body got any ideas as to where to look for the issue? I hope it isn't something more serious that dirty carbs or an extreme level of jetting.

[tkent02]

Finally got it to stop backfiring by turning the air pilot screws out like 6 FULL turns.

These are not air screws, they are mixture screws, out is richer.
So if some pilot jets or something were partially blocked, opening the screws six turns out may be making it closer to a correct mixture. Would make it too rich at other times. Compensating for one problem, by making another. Like when you pinch a child's nose to make him open his mouth.

Dip the carbs.

[rustybronco]

Carb sync - couldn't get it right, the bike has a 4 into one Kerker pipe and a uni filter. this makes me think the bike's carbs may be jetted too, but haven't taken them apart to find out. Finally got it to stop backfiring by turning the air pilot screws out like 6 FULL turns. This seems crazy, but it's running better. I haven't yet checked the plugs to see if it's too lean

+1 on the above.
when you are in the carbs, check the jet sizes.
you do know the plugs are the window to the motor, don't you?

[taochaos]

These are not air screws, they are mixture screws, out is richer.
So if some pilot jets or something were partially blocked, opening the screws six turns out may be making it closer to a correct mixture. Would make it too rich at other times. Compensating for one problem, by making another. Like when you pinch a child's nose to make him open his mouth.

Dip the carbs.

The 4 screws that are on top of the engine side of the carbs? What are the air screws then?

Thanks for your help, haven't ever needed to mess too much with carbs before other than syncing them

[taochaos]

+1 on the above.
when you are in the carbs, check the jet sizes.
you do know the plugs are the window to the motor, don't you?

Well, I checked the plugs when I did the compression test, but not after all this fiddling with the carbs. They looked fine at that time, nice light brown color. But the bike was backfiring and smelled rich.

[rustybronco]

Well, I checked the plugs when I did the compression test, but not after all this fiddling with the carbs. They looked fine at that time, nice light brown color. But the bike was backfiring and smelled rich.

6 turns out on the idle fuel mixture screws, I guess so!
considering it smelled rich before.

The 4 screws that are on top of the engine side of the carbs? What are the air screws then?

there are no air screws, only idle fuel screws.
what do the plugs look like now? pictures of them?

[taochaos]

6 turns out on the idle fuel mixture screws, I guess so!
considering it smelled rich before.

there are no air screws, only idle fuel screws.
what do the plugs look like now? pictures of them?

Doesn't smell rich anymore... after 6 full turns out. I will take pics of the plugs when I check them on th. at my buddies garage.

[taochaos]

So I am now soaking them in carb cleaner overnight, we will see if I need to dip them. I figure one thing at a time.

[taochaos]

So, I soaked them in carb cleaner and the idle is much smoother now. It is still backfiring and this hasn't changed.

I was talking to a friend and mentioned it only backfires when decelerating. He said this may be related to the intake boots on the carb having an air leak. Does this make sense to anyone else?