Jets for GS1000 carbs

[Guest]

A friend of mine was given an 81 GS850 but the carbs are from a 1000. I told him Id try to help him get it running right but Ive really just started with bikes myself. Ive done some searching and see it probably just needs jetted right, but I have no idea which ones. Its all stock. From what hes told me, if he covers the intakes with his hands itll start but good luck keeping it running, thats about all ive gotten from him. Was a short convo. Any ideas and tips? Thanks

[JTGS850GL]

The 1000 carbs are BS34SS (34mm intake) while the correct carbs for the 850 are BS32SS (32mm intake). The 1000 carbs will not bolt up to the 850 unless the intake boots have been altered or stretched WAY out. Suggest you try to swap out the 1000 carbs with 850 carbs from a member here or sell them on ebay and pick up another set. Very likely the carbs you have will need a complete strip and dip as well.

[Big T]

Let's see - 2 newbies trying to help one another. A noble cause

Jets aren't your issue

Not having the airbox on the bike is #1. Not knowing the maintenance, or lack thereof, is #2

The carbs won't run well without the airbox on. If he's removing the airbox, then it does need to be rejetted. And carbs cleaned. and valves adjusted and well, that's why there's a Top 10 Newbie Mistakes list here

You've come to the right place. But we'd need a lot more information on what's he's done and what he intends to do to the bike to give you a well informed answer

[JTGS850GL]

Yippie, now I'm a newbie again. So old great wise one... What did I say that's so wrong? The GS1000 carbs are not the correct carbs and will have issues with bolting up unless the boots have been altered. The BS34 carbs are 2mm larger on the intakes and do not have the same centerline. The extra 2mm is skewed toward the outside of each carb. If he's got them mounted using the stock boots then those boots are pretty stretched on the outer side. If they're old they will certainly crack. My question is, how does he know they are even GS1000 carbs?

Of course he needs to either get a proper air box installed or re-jet for pods. The issue I see is, he needs to start out with a good baseline or nobody is going to be able give him a jetting answer and the Dyno-jet kits are sized to specific engine/carburetor combinations. Pilot air jets are different as are the needle jets.

[alke46]

I think he was referring to the OP being a newbie trying to help out another newbie.

[JTGS850GL]

I think he was referring to the OP being a newbie trying to help out another newbie.

Not so sure about that. I apologize for the sarcasm if so.

[Big T]

I think he was referring to the OP being a newbie trying to help out another newbie.

Ahem

Curb your ego

[lrndthehardway]

As far as noobie yes, we both are, but Ive at least worked on cars for years where as he hasnt so I have that. Ive just started riding a couple of months ago on a honda shadow, and he was given the 850 but doesnt even have his license yet. He said he cant get it to stay running unless he puts his hand over the carb boots. I havent even been over to look at what hes got going on but Im headed over now.

He got the bike this way so Im sure he has no clue whats been done to it, but he was told he had the other carbs on it. Im going to pull the numbers off of it when I get over there. Right now it sounds like since itll run if he puts his hands over the boots or whatever hes doing that, obviously the airbox is off so Ill start with that. When I get more info later Ill post back.

[lrndthehardway]

Not sure if my other post posted so here I go again. Will run forever with choke held out, should we have to hold it out? It slowly closes by itself and will stall.

It has pods installed, not sure if it was rejetted yet, what would stock be, and what should they be with the pods on.

Itll only start if you have panty hose over carb inlets under pods

Lots of raw fuel in carb where pods install

Twist the throttle and it seems like its fuel deprived, only did this with choke out tho, would that matter? If its rolled on slowly its ok, but just a quick twist and its bogging down.

When it starts with choke on, it seems like it has to wind up until its running, not a normal start at all

If you hold choke open itll run forever, until you let go and it starts to close.

Sounds fuel related but not sure where to start. Filters? Jets? Carbs were cleaned a couple of times already according to PO.

[tkent02]

Start at the beginning. Take the carbs off, figure out what they are, and which jets are in them. Do they even fit correctly? Are they CV carbs? Most 1000s came with VM carbs, completely different. (CVs are the ones with the flat tops with four screws)
Let us all know what you have, pictures are good.

Whether or not you use them or find the original carbs, clean them thoroughly as shown on Basscliff's site. Put in new o rings, and appropriate jetting, get the air box on there sealed correctly and start tuning.

It would all be ever so much easier if you found a set of the original 850 carburetors, all the thinking has been done already by engineers far smarter at this stuff than us...

People on this forum have barrels of carburetors laying around, find some.

[lrndthehardway]

Hopefully this pic helps, not sure if this is the flat top you were talking about, sorry its sideways, forgot to edit

[Big T]

That's a CV (BS series) carb

Reclean and check to see if the pods are blocking any of the ports in the carb mouth

Otherwise, pilot circuits blocked

[steve murdoch]

Everything you need to know about cleaning your carbs.

http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

[bomber737]

The 1000 carbs will not work on a 850 engine. The 1000 engine spacing is wider so if you have managed to wedge the 1000 carbs in those intake boots you have a huge amount of air leaking, not to mention the extra air from the pods. An 850 airbox will certainly not work with the 1000 carb spacing. Ask me how I know this......I have a 850 airboxe you can have for shipping cost. Il send yo the best one, its just sitting in my basement. You certainly need the correct carbs for the 850. Clean them as per the cleaning guide, replace o-rings, properly gap you valves and that bike should fire right up. What you have there is a 35 year old bike thats had 5 years worth of maintenance done. You have 30 years of neglect to catch up on. Good thing our GS'S are so resilient. Take your time, do it right the first time. good luck

[lrndthehardway]

Thanks for the offer on the airbox, Ill let him know, as far I can recall, I think he said he has the 850 airbox but Ill double check. How can I tell by these carbs if they are the 34 or 32? Is there a stamp somewhere or something I can see without removing them ? By eyeballing it, it didnt look to me that these were forced on, I didnt see any abnormal stretching of the boots etc but Im no expert.

If they are 1000, Im sure hed be open to trade someone for the correct carbs