carb issues on 80 gs1000g

[willmcdonough]

i just got a new (to me) 1980 gs1000g. it had been sitting neglected for sometime and needed some attention. I put everything back into order and cleaned the carbs and reinstalled them. The stock intake manifolds and ok, but i will need to replace them soon- does anyone know where i can get some in seattle? Anyways I got the bike started and it idles/starts up no problem, BUT when I rev the motor up to 5,000 rpm it bogs down and will not exceed this engine speed. When watching the slides in the carbs - as i rev it to this 5,000 rpm limit, only 3 of the 4 move upwards. I was wondering if anyone had an idea of what might still be clogged or any insight into. Everything inside the carbs looked to be in good shape when i cleaned/dipped them, I suppose one cleaning just may have not been enough and they need another.?
Anyhow, thanks for any input and great site by the way...Will

[chef1366]

Sounds like dirty carbs or weak ignition to me.
If you push up on the slides do they return quickly and all the same?

[willmcdonough]

when i push the slides up the all return at the same pace- not real quickly, but evenly. I did notice that the white wire that connects to the rectifier seemed to be getting quite warm during warm up. Not sure if thats related or not. When observing the spark produced at the plugs - it seemed very bright and looked good. All I can think is that the carbs remain dirty,I cleaned then #2 & #1 had some very nasty, sticky, dark, oily substance in the bottom carb bowls. #3 #4 looked like someone had already cleaned them...

[KitKat]

lubricate the slides and see if that helps? WD 40 works, but don't get it on the rubber seal

[chef1366]

I've seen that exact problem happen because of a bad igniter.

[Sudds]

If you are looking for the carb nipples that fit the cylinder head I have a set. I was getting an airleak and ordered a new set. After I got them they weren't much better than the ones I had which were almos in as good. Turned out all I needed was new O rings which I now have a supply of. If interested let me now at BSudderth@juno.com.

[bwringer]

Just guessing, but if you can see the slides moving, I bet the airbox isn't installed.

Without an airbox, you'll get exactly the behavior you're reporting. The bike won't rev and will generally run like poop.

Seal up the airbox sides and air filter carrier with weatherstripping, clean and very lightly oil the filter element, install the airbox, and report back...

[Big T]

Just guessing, but if you can see the slides moving, I bet the airbox isn't installed.

Without an airbox, you'll get exactly the behavior you're reporting. The bike won't rev and will generally run like poop.

Seal up the airbox sides and air filter carrier with weatherstripping, clean and very lightly oil the filter element, install the airbox, and report back...

What he said

Your carbs need more vacuum to pull the slides all the way up. They're very sensitive to that.

[BassCliff]

Hi,

Yep, with the stock jetting, your bike needs a tightly sealed airbox installed. Here's what I did to my airbox sidecovers:



Do the same, as Mr. bwringer suggested, to the top of the air filter cage. You might even need new airbox boots, carb intake boots and O-rings. Check this out...

Air Intake Repair
Airbox removal, intake boots and O-ring replacement

It's a PDF file I just put together documenting the whole procedure. You can also have a look at Mr. roostabunny's airbox fix-up...

Airbox Sealing
(by Mr. Roostabunny)

...and Mr. bwringer's information on O-ring replacement...

Replace intake boot o-rings

Then have another look at the required maintenance lists in your "mega-welcome", just to refresh your memory. Keep us informed. We'll help you keep your classic GS on the road and running properly.


Thank you for your indulgence,

BassCliff

[Jon]

Hi,

Yep, with the stock jetting, your bike needs a tightly sealed airbox installed. Here's what I did to my airbox sidecovers:



Do the same, as Mr. bwringer suggested, to the top of the air filter cage. You might even need new airbox boots, carb intake boots and O-rings. Check this out...

Air Intake Repair
Airbox removal, intake boots and O-ring replacement

It's a PDF file I just put together documenting the whole procedure. You can also have a look at Mr. roostabunny's airbox fix-up...

Airbox Sealing
(by Mr. Roostabunny)

...and Mr. bwringer's information on O-ring replacement...

Replace intake boot o-rings

Then have another look at the required maintenance lists in your "mega-welcome", just to refresh your memory. Keep us informed. We'll help you keep your classic GS on the road and running properly.


Thank you for your indulgence,

BassCliff

This info is EXACTLY what i needed - all of BassCliff's stuff is superb, thanks for producing it all. I thought I'd post this just to get it back into the topical section, as so many people seem to have these airbox sealing troubles. The photo is a big help (to me anyway).