Tuning carburettors on GS850G -82

[noratx]

Hi!

I have just bought a "new" GS850G -82 since my last one, sadly decided it had done enough after 130000 kilometers.
The crank bearings seems to be gone since it sound like a jackhammer when passing 3500 rpm.

I was about to buy a new crank, and found someone wanting to sell me a GS850G -82 for litterally nothing. Thought I should just make an engine swap or use it as spare parts bike..
BUT, turns out it is in SOOOO good condition, that using in for spare barts would be a stupid mistake.
Instead, I will at a later time buy a new crank as originally thought and just have 2 bikes.

However, the only bad think with it, is that the carburettors was apparently damaged when the PO got it, so he picked up a GS1000 carburettor manifold and used it instead, without adjustments.
(He had 5 other bikes as well, and didn't get to actually tune it and forgot about it for a year in a shed until he found me wanting a new one).

So... here comes my question..
A GS1000 (model unknown) carburettor manifold on the GS850G, what kind of adjustments would I need to do, except for possibly synchronizing them?
It seems to be going rich, since the sparkplugs are more or less black.
I have not yet checked the air filter, but could be that it is old and does not let through enough air, so obviously I need to check that first.
But lets for the sake of it say that I put a new filter in, and it still goes rich, what do I need to do?
Changing the air screw settings? Or find new jets?

My old GS850G are going well, however, I don't know any of it's previous history. PO has put a 4-1 system on it, so might be that he have re-jetted it for the new exhaust (although, it is kicking sometimes in the airbox, so might be that he havn't and I just never got to it)

I have thought of just moving my GS850G carburettor manifold over to the new bike and hope it won't go as rich, and that's probably what I will try first as a quick fix before the season ends (season in Sweden will be over in ~1.5 - 2 months).
But would like to do it up properly during the winter.. so, question remains, where do I start?
And when looking for fouling on the plugs, do I need to take it out for a ride? Or would it work just riding in the garage? (Thinking of if I do that kind of work during winter with icy roads. I'd prefer not to take the bike out risking to slip).

Uhm, any ideas and constructive comments are appreciated..

Thanks!

 

[Nessism]

The 1000 uses 34mm carbs whereas the 850 came with 32's. I'm kind of surprised that guy got the bigger carbs to fit on the smaller engine.

Sorry, but not sure what to suggest other than reading the plugs and attempt to rejet. Or, get the right carbs. I'd install your old carbs on the new bike and kick the can down the road until you get time to fix the old bike.

 

[noratx]

Hmm.. as from what it looks like, they seem to sit there without any midifications..
So maybe he is wrong then and they really are 850's.

But I will probably do as I thought and that you suggest, Nessim, to just pit my old 850 manifold there and hope I don't need to work too much on them until the end of the season.

My god, for the money I paid for the machine, I have found a real bargain. The engine of the "new" bike sounds like and behaves like a brand new engine. No noises or rattles, except that it is running rich.

 

[Who Dat?]

The BS32 carbs on the 850 and the BS34 carbs on the 1000 use the same jet sizes, so I would guess that if they were, indeed BS34 carbs, you would need to go down a bit, maybe to 110 mains. They both use 40 pilot fuel jets, so again, you might need to drop that to 37.5. The pilot air jets are different, the 1000 uses 160, the 850 uses 180, not sure which way to adjust, or how much.