GS1000S Cam shaft + carbs?

[Jackbob]

I recently overhauled the top end of my 78 GS1000HC and all is very well, however I came across a GS1000S (1980 "T" model year i think) Cylinder head complete with cams and carbs fitted in good nick for sale which i bought.

The S head has the higher lift inlet camshaft and the carbs are 30mm bore up from std 26mm for my bike) VM Mikuni smoothbores.

I am considering installing the S cams and carbs onto my existing head (as it has just been overhauled). I do not know if the valves are the same diameter, or the ports for that matter, as there does not seem to be a lot of info around, and apprently different countries received differing specs.

My S head would be an Australian/NZ spec probably 1980 pre CV carbs. I am running std exhausts and airbox.

Anyone done this conversion?

[sharpy]

head

The 1000ST head should have a 6mm hole at the front to acecpt a bolt that the previous model doesnt have. Just in front of the cam chain tunnel. Cant remember what size the valves are but the carbs will fit.

[Jackbob]

Thanks Hampshirehog and Sharpy for the info.

I have now had a better look at the head and carbs i purchased;

Head has std valve head diameters - 38mm and 32mm
Seems to have larger inlet tract diameter.
Inlet manifold screw spacing looks slightly wider than 1000E head.
Carbs are more like 32mm (VM?) Mikuni not 30mm as i had thought.
Carb bowls are highly polished inside, and the float is of all brass construction - unlike the VM26 carbs.
Head has the extra bolt hole like Sharpys photo.
Carbs look to be too big for the existing VM26 airbox manifolds.

Obviously the GS1000ST Australian model would have flowed better than the std E?

Odd that they didnt go the CV way like the UK spec. Perhaps homogated for local racing?

Thanks.

[psyguy]

some info here:

http://www.suzukicycles.org/All-Suzuki/all_suzuki_models.html

(for aussie model s)
The '79 'SN' series GS1000 had the full plastic dash with oil temp and fuel gauges and ran 28mm Mikuni slide carburettors. The '80 'ST' series looked the same but only had a speedo/tacho binnacle with a fuel gauge in one of the instruments, not the full plastic dash. The 1980-year's model also had 30mm Mikuni slide carbs, as well as bigger camshafts with about half a millimetre more lift and longer valve duration. “To my knowledge, that model was the only GS1000 to ever benefit from the larger camshafts and slide carburettors, and definitely made more horsepower than the previous model


cv carbs were generally introduced for the first time in 1980 for most models, however aussie model s still had vm carbs in 1980

in my (limited) research i have never come accross the info on different inlets on 1000 models, its only 1100 that had bigger inlet i think

that extra bolt in front of the head was added (on most larger models i think) in 1980


btw, sent you a pm some time ago, my Bruno is keen to meet your beast

[hampshirehog]

The CVs were really only put on to meet emissions laws, so I suppose with Oz being a big place with a relatively low population no one down under was fussed about pollution - slide carbs were the preferred type for racers.

My 79 SN has got the extra bolt in the head - I can't remember whether I've seen this in other UK 79 or earlier 1000s.

The brass floats are unusual - I thought by that time (and some time before) Mikuni had switched to plastic across the entire range.

The other thing that interests me is that Sharpy's head has got S5 stamped on (above made in Japan) - mine has got S2. Was there ever a 1,3 and 4 and what do the numbers mean?

Jackbob if you want to post your head and ancillaries over to the UK I could compare measurements for you - I promise I'll post back (in about 20 years time after 'thorough testing' :-D)

[Jackbob]

Well i guess its definitely an 80 GS1000ST head and carbs - Aust spec. Thanks for the replies.

Note that this head is stamped "S1"!

The inlet port tract diameter and spacing of the 2 manifold screws is definitely larger than the GS1000EC head. I would need to replace the head and carbs as a unit to upgrade. For example the distance between the 2 screws on the EC head is about 63 or 64mm, whereas the S head is 68mm (kind of makes sense given the larger bore carbys.

Also my bike has been fitted with a later (80 model perhaps with the higher set badge and no fluting, and smaller fuel tap) tank and i suspect also that there could be problems getting the carbs to physically fit in as they appear a little taller (currently about 3mm clearance between the tank and the carb tops with the VM26 carbs). I think the tank on the bike came off a CV carb model.

[Jackbob]

Here's a shot of the carb float

[focus frenzy]

yep, the intake ports are larger on 80 model 1000S and G's.
that makes for a nice boost in power.

[srsupertrap]

That is a interesting photo. Your brass floats are similar to the Mikuni VM29 Smoothbores and you have a pilot fuel screw like the VM26 & VM28.

I have never seen a fuel bowl polished on the inside? That secondary operation had to add expense . . .

[Jackbob]

Thanks for the answers.

I have another question - could someone please elaborate for my benefit the difference between a smoothbore carb and a (standard) VM slide carb or are they the same thing?

I have referred to the VM26 in the past as a smoothbore - is this incorrect?

Thanks

[sharpy]

Thanks for the answers.

I have another question - could someone please elaborate for my benefit the difference between a smoothbore carb and a (standard) VM slide carb or are they the same thing?

I have referred to the VM26 in the past as a smoothbore - is this incorrect?

Thanks

This is the easiest way to tell a smooth-bore, Has 17mm nuts on the bottom.



And you look down the "barrel" its straight not curved like normal ones.

[Jackbob]

Thanks Sharpy - mine are therefore not a "smoothbore" type.

[sharpy]

carbs

Yours still might be the original 1000s carbs which are getting rare anyway. There are the biggest carbs suzuki make and i think they same carbs that came on the NZ version Katana they used for the 6 hr race.

[psyguy]

thats a cool avatar sharpy, can you indulge us with a big pic??? :-D

Yours still might be the original 1000s carbs which are getting rare anyway. There are the biggest carbs suzuki make and i think they same carbs that came on the NZ version Katana they used for the 6 hr race.

[sharpy]