Probably street ride-ability might be better with small carb ut there are many other variables to consider with this before making that assumption. Probably more of a consideration than stock carb size for a race bike would be the valve change in 1980, this is from the link I posted in your wanted ad.

<div align="left">The history of the GS engine

Initially, the basic GS engine design underwent a few stages:

the quintessential GS, an air-cooled, two-valve-per-cylinder DOHC engine, which set Suzuki off as a serious competitor in the UJM market, and a good one to boot! This design was first introduced in the late 70's.

the 4-valve-per-cylinder GS, introduced in 1980, which had basically the same air-cooled engine, but with another cylinder head, featuring 4 valves per cylinder and a reworked combustion chamber (TSCC). In Europe and Japan, these models were known as the GSX's.</div id="left">

 

How did I miss that valve change? Thanks Nic.

Bottom line is...
to build the most reliable and race-able GS1000 I'd ideally want only the 1980 GS1000S (or was the 4-valve put on all GSs?) and fit it with the 28mm Mikuni VMs?

 

I wonder if that site is correct as I see elsewhere where both 79-80 having 4 valves per cylinder.
looks like 1000 is 8 valves 1100 16 valves.

<center>Make Model

Suzuki GS 1000S
Year

1980
Engine

Air cooled, four stroke, transverse four cylinder, DOHC, 2 valves per cylinder.

Capacity

987
Bore x Stroke 70 x 64.8 mm
Compression Ratio 9.2:1
Induction

4x 28mm Mikuni VM 28 SS carbs.
Ignition / Starting

Electronic / electric
Max Power

90 hp 65.7 @ 8200 rpm
Max Torque

8.5 kg-m @ 6500 rpm
Transmission / Drive

5 Speed / chain
Front Suspension

Telehydraulic forks
Rear Suspension

Swinging arm forks with adjustable shock absorbers.
Front Brakes

2x 295mm discs
Rear Brakes

Single 295mm disc
Front Tyre

3.50 V19
Rear Tyre

4.50 V18
Dry-Weight

238 kg
Fuel Capacity

20 Litres
Consumption average

15.4 km/lit
Standing ¼ Mile

11.7 sec
Top Speed

223 km/h / 138.5 mp/h</center>

 

The short answer is None of the above.

What class/organization are you planning to race in and what do they allow? A set of GSXR flatslides would be an upgrade as long as you can get away with them, or CR31s

 

Thank you for the help -

I'm going through the initial planning to decide on whether I can afford (and have the ability) to build a WERA V5 bike. I'm approaching it as a 4-year build. I've narrowed it down by bike and this is the one I'd build if any - doesn't really matter what class/organization. Not looking to be ultra competitive - although besting a K1000 would be awesome - just trying to check off a bucketlist item. I know Tommy-D is in V5 so I may be able to learn from him until he gets more than two turns in front of me.

Would go +3mm pistons just to start with newly honed cylinders. I'm hoping the questions below would tell me just how much else I'll need to spend.

• Can I stay stock carbs?
  CR35 Keihins are around $900.
  Mikuni 40mm go for about the same.
• Can I stay stock valves?
• Can I stay stock suspension?
  Looks to me that the suspension could remain stock except for the addition of new springs/oil and a fork brace up front and slightly changing the angle of the rear mounts.
• 520 conversion, new brake pads, sticky rubber and she should be ready for the track?

 

Back in the early/mid 90s my buddy that has my old 82 Katana put(IIRC) 88-89 GSXR 750 carbs on it. Woke it up big time everywhere.

 

4 valve 'GS' was available as 1000 in USA because of the superbike race class
Europe had 1100 (I believe power output was the same but 1000 had slightly less torque)
Everywhere else it was a GSX to denote 4 valves /cyl.
Quickest way to identify is from side on pic of cylinder head.
GSX has screw adjusters and a 'square' chrome cam end over.
2 valve GS motors have shim over bucket and round cam end cover
29mm or 31mm Mikuni smoothbores may be best carbs to use as there is information on them on the Suzuki 1000's
It gets quite expensive to get them to a genuine 100 RWHP but it makes a really nice street bike when you do (The 90bhp quoted is crank not rear wheel)

 

2V gs cv type head have bigger intake port.
My gs1000 have a 1100 kit in a gs1100g block with a gs1100gk head.
the gk head have the exhaust shaped like the 1150 head, a D shape.
vm33 with big port head and a piston kit are good.
the best carbs are the mikuni rs.
if the motor is stock try to find a set off a first gen gsxr750 canadian model or a set of old 29 smoothbore.

Marc

 

I think the gs1000s 28mm where only available in europe and australia
Marc