GS850 gasp when accelerate

[Guest]

Hello all,

I bought a GS850 1981couples months ago, and the bike is in pretty good conditions, just 5K miles used since new, but I has a problem, the engine start easy and idles well but when I accelerate it, it doesn't go above 3 to 4K rpm. As it is being stopped or years, I decided to clean the carburetors, them I noticed that it was without the air filter foam.
I bought the filter, gaskets, orings and disassembled the carburetors. As expected due to the low mileage, everything was new, probably the first time it was serviced. I noticed that the pods were dry and cracked, so I bought new ones.
After all was cleaned I re-assembled the carbs and filter in the bike, started it, and the problem remain the same...
One thing that I`m in doubt is the filter assembly in the air box, the filter metallic body (that holds the foam), does not have a gasket on the sealing face to the air box, and I think it should, because there is a gap (round 1/8") between this filter metallic body and the air box, and that can influence the vacuum and the air/fuel ratio. I tried to find a picture of this filter to check if it has a gasket there, but didn't found.
I would like to know if my hypothesis (missing gasket causing the issue) makes sense, or if there is something else that could be the cause.

Thanks for your help

[Big T]

Air gaps can cause that problem
How are the gaskets on the air box end caps?
Did you follow the tutorial when you cleaned your carbs?

[Paulo Perez]

Hello. Yes, I fully read the tutorial for the carbs cleaning.
It does not have gaskets either between the metallic body that supports the foam and the air box (só there air that pass through the gap, bypassing the foam of the filter) and also does not have gaskets on the air box caps.
As I didn’t found the gaskets to buy I’m planning to do them using rubber. Do you have any suggestions on this? I didn’t found any picture of this filter assembly, do you have any?
thank you very much for you support!

[Burque73]

Hello. Yes, I fully read the tutorial for the carbs cleaning.
It does not have gaskets either between the metallic body that supports the foam and the air box (só there air that pass through the gap, bypassing the foam of the filter) and also does not have gaskets on the air box caps.
As I didn’t found the gaskets to buy I’m planning to do them using rubber. Do you have any suggestions on this? I didn’t found any picture of this filter assembly, do you have any?
thank you very much for you support!

Here's a complete air box from an 81 850G. You can at least see what the black rubber seals look like that go under the chrome ends and the filter basket with a foam filter on it. Peel and stick weather strip from the hardware store works instead of the rubber seal on the ends. I also used some of that weather strip around the top of the filter basket.

Here's a good drawing and a resource for parts. https://www.partsoutlaw.com/oemparts...ce/air-cleaner

[2BRacing]

Hello. Yes, I fully read the tutorial for the carbs cleaning.
It does not have gaskets either between the metallic body that supports the foam and the air box (só there air that pass through the gap, bypassing the foam of the filter) and also does not have gaskets on the air box caps.
As I didn’t found the gaskets to buy I’m planning to do them using rubber. Do you have any suggestions on this? I didn’t found any picture of this filter assembly, do you have any?
thank you very much for you support!

Hi Paulo

Yes, that gap between the filter and the airbox should be sealed. Stick foam "weatherstrip" onto the airbox, and when the filter is mounted it will seal up against that foam strip.

Here is a guide on how to seal your airbox. http://members.dslextreme.com/users/cbsaunders/gs/airbox-sealing.pdf

Good luck!

[Paulo Perez]

Thank you for your help!

[Big T]

Let us know how it works

[Paulo Perez]

Sure, I`ll work on it on Saturday and post the results here. Thanks!

[Paulo Perez]

Worked very well, I sealed the air box gaps, cleaned and oiled the air filter, reassembled on the bike and it is running perfectly now.

Thanks for the help!!