GS850 Carb fluttering and bogging down at 60mph

[Guest]

Hi all, looking for some help please!!!
I bought some vaccum carbs from a GS850 to put on my bike, They have been cleaned and rebuilt and are now on my bike however when i started my bike it runs ok on the choke and it good on the bottom end but when i get it any gas it just bogs down after 60 mph... The slides are not going up very well and are really fluttering... What have i missed out on when doing the carbs or is there something else i am not doing right???
The only thing that i have done do my bike apart from the carbs is new piston rings and a decoke..

Desperate to get it sorted

Cheers All

Sam

[Redman]

Sam, Welcome to TheGSR.

.................
............................. to put on my bike, .............

And which model is that...? (maybe add that info in your signature line, then it shows up in every post).

Can you go higher rpm in lower gear?

Describe about your airbox (or lack thereof).

[Welshbird]

Thanks Redman,

It is a GS850G

i can only go very slightly high rpm in lower gear.

Airbox, is a custom one that i have had on my bike for a while.

[Steve]

Did it ever work well with your custom airbox?

These carbs are rather sensitive to turbulent air coming into the carbs, so smooth airflow is critical. A stock airbox has individual runners that resemble velocity stacks. Even most (decent) pod filters have a tapered runner that helps smoothe the flow a bit. With a "custom" airbox, there is no way to know.

Just so you know, the slides in the carbs do not control airflow, they respond to it. If you can see the slides fluttering, it seems obvious that you don't have the airbox on, and it will NOT run smoothly.

.

[tom203]

Did it run ok with previous carb rack..and this custom airbox? How about a pic?

[bwringer]

One thing I've seen cause this sort of thing on a stock GS850 is the ends of the vent tubes are hanging out in the airstream. They're supposed to be tucked behind the airbox in the little clip provided. If the ends are in the airflow, you'll get all sorts of odd stuff.

But with all the other unknown factors here, uh... I dunno. As Steve mentioned, turbulence in general causes all sorts of odd issues for CV carbs.

In a stock GS850, the airbox MUST be sealed for proper airflow. That means air only gets in the airbox and past the filter where it's supposed to get in. And it also means the snorkel on the back of the airbox MUST be in place and intact.

With your mystery setup... impossible to tell what's happening.

[Nobody]

I have the same problem but with a stock airbox on an 85 GS850G with CV carbs

[Steve]

I have the same problem but with a stock airbox on an 85 GS850G with CV carbs

Where are you?

As far as I know, '85 850s were not available in the USA, but I don't know where all they <were> available.

.

[Nobody]

Just re-checked the registration papers and yep its built in 85 and registered on the road here in 86
Here being Germany not that that matters much really

[Steve]

Well, yes, it does. German air behaves considerably different than American air.

I still have a question, though: How can you tell the slides are fluttering? The only way to see that is to remove the airbox. If you remove the airbox, the slides WILL do strange things, but the bike will be rather unrideable in that condition.

OK, German air might not be all that different, but if you were to ask about where to order something, we would not have the slightest clue that what we were recommending would be on the other side of the globe.

It would be handy for those who respond to your queries to know where you are and what bike you are talking about. Don't need an address, but editing your profile to show a town or region would help. Also handy is creating a signature that mentions your bike. Does not have to be anything fancy, just a simply "Current bike: '85 GS850G" would be good.

.

[Uncamitzi]

One thing I've seen cause this sort of thing on a stock GS850 is the ends of the vent tubes are hanging out in the airstream. They're supposed to be tucked behind the airbox in the little clip provided. If the ends are in the airflow, you'll get all sorts of odd stuff.

But with all the other unknown factors here, uh... I dunno. As Steve mentioned, turbulence in general causes all sorts of odd issues for CV carbs.

In a stock GS850, the airbox MUST be sealed for proper airflow. That means air only gets in the airbox and past the filter where it's supposed to get in. And it also means the snorkel on the back of the airbox MUST be in place and intact.

With your mystery setup... impossible to tell what's happening.

The Snorkel? My airbox has an opening in the back...but it's just bare metal... Am I missing a part?

[Steve]

I just happen to have my airbox off, I'll grab a quick picture for you.



.

[Uncamitzi]

Well, that's not good. Any ideas on what, where and how I can find a replacement? I'm already done an Ebay and Amazon search.... Will check the boneyard this week.

[Steve]

Can't order that part, the only thing I can think of is to watch eBay or check the boneyards.

Most of the larger (850+) shafties have that snorkel, so that might expand your search a bit.

.

[Uncamitzi]

Can't order that part, the only thing I can think of is to watch eBay or check the boneyards.

Most of the larger (850+) shafties have that snorkel, so that might expand your search a bit.

.

Are the 80, 81, 82 airboxes interchangeable? From what I've read the GS750s have many of the same parts.. And I also guess the "L"s have a different box than the Gs.... ?