VM33SS carbs - GS1000S

[Jackbob]

A while back i picked up a nice set of Mikuni VM33SS carbs + big port head from a dismantler. A search of previous forums has confirmed that these probably came off an '81 GS1000S (Australian specification).

Anyways - does anyone know how much H.P. (published by Suzuki at the time, or an actual dyno figure) these 81 "S" engines made?

I know the standard GS1000E with 28mm carbs supposedly cranked out about 90H.P.

I plan to utilize these one day on my GS, or perhaps build up an S replica.

Thanks.

[rapidray]

You can figure on about 80 at the back wheel on a stock motor with 4 into 1, those carbs & all of it tuned correctly. Ray.

[first timer]

are you talking 8v or 16v motor the gs1000s can mean 2 differant things depending where you live.
it can be a kat gs1000sz 16v or a gs1000s wes cooley replica 8v

[rapidray]

8 valve = 80. 16 valve = 100. Both at the back wheel, same setup. Ray.

[psyguy]

jackbob mate, your ol' zook not pullin' as hard as the new triumph?

seriously though, a respectable german site states no difference in engines between the S and the other models
it only shows an upgrade in carbs, from vm26 to vm28

http://www.gs-classic.de/index1e.htm

you are probably talking about an aussie only spec, i would guess a small production intended for racing circuits - may be difficult to find a genuine suzuki data for that bike

[Mike Derrett]

Mr Jackbob,

1980 GS1000ST Aussie spec has vm30ss carbs, not 33's. Looking at the Suzuki book, I'm not sure I want to argue with the Germans but it also has higher lift cams (8.5 compared to 8mm inlet and 8 compared to 7.5 exh ) than the E model. Also had different cam timings. Surely that's got to mean something must be different.

I know my one certainly goes faster, but that's 'cause it's red.......

[hampshirehog]

The E over here had VM28SS as well as the SN. The STs alone had higher lift cams (SNs didn't).

SN intakes - 36.24 ST intakes - 36.80
SN exhaust - 35.79 ST exhaust - 36.30

Some also had different valve timing - check the picture:

UK STs had CV carbs but those lucky Antipodeans got the bigger VM30SS.

There were many variations of SNs and STs across the globe and some bikes as far as I can tell didn't end up in the country they were meant to. Therefor there's probably no such thing as a definitive GS1000S. Only one thing I know for sure - red ones were faster

[Jackbob]

Thanks for replies

Sorry been unable to get back to this thread until now.

Thanks RapidRay for the H.P. figures.

First timer - is an 8V head.

Mike - yeah i think the carbs must in fact be VM30 ex Aussie/NZ model ST, not 33mm.
I wanted to post a new photo with vernier but camera wont co-operate. A digital vernier measurement of the carb throat is definitely close to 33mm however. I have posted an older photo of the same carb/s.

Hampshire - The valve timing diagramme may explain why my manual (Haynes UK published in 1980) seemed to have a mistake in regards to the pin count on the cam chain. I set it as per a Suzuki workshop manual i have also. A photo in the Haynes manual relating to the pin count was correct however.

Question ; If you inadvertantly set the cam timing 1 tooth out would it run at all??

And Psyguy - great ride today - good to catch up with you guys. Bike ran really well all day - until...... please see new thread titled "plugs fouling cylinders 2 & 3".
Ha Ha the Sprint is great - but the GS is a hell of a lot of fun - and attracts more interest out n about. I cant get over how well the old girl handles + corners - thanks to ikon shocks + progressive springs in the forks.

Thanks Y'all.

[Old Colt]

Question ; If you inadvertantly set the cam timing 1 tooth out would it run at all??

Most engines have enough valve to piston clearance so it will not crash so yes it should run. Performance will vary. Some engines will crash the valves.

I could not view your picture.

[Steve]

Question ; If you inadvertantly set the cam timing 1 tooth out would it run at all??

Yes, it will run, but as Old Colt mentioned, performance might be different.
Actually, it will be different, you just might not notice it.

If you lined up the mark to pin 20 instead of pin 19, the intake cam will be retarded by several degrees.
This will enhance high-speed operation, but will degrade idle and low-speed performance.

If you lined it up the other way, you would have enhanced low-speed operation at the expense of high-speed power.

I don't think the clearances on these engines are so tight that being off one tooth (maybe even two) is going to bring the valves into contact with the pistons. I have never gone to the trouble of actually measuring the clearance between valve and piston, but when using the zip-tie method of changing valve shims, the valve is open farther than it would be if the cam timing was off a tooth, and there is no contact.

.

[Jackbob]

Photo

Sorry - now attached i hope - note size - is 33mm. Calipers were definitely set to zero before measuring. Intake port in the head is also 33mm diameter. Is this a VM30 carb or ?

[Jackbob]

valve timing

Steve, Old colt re the timing/pin count.
I wonder - Bike is actually not running all that great at low engine speed + keeps fouling plugs, plus has a small pop from the LH exhaust at idle...now i am not so sure in my mind that i have the timing correct as i has assumed a mistake in my manual due to conflicting info from 2 manuals. Think i had better re check it. bugger.

[Old Colt]

Those carbs should turn out to be 30s, there is a taper in the bore. Try to nestle the caliper in as far as you can and check, it should be down to about 31mm deeper in.

On the cams, with the valve cover off, take a look at the two cams from the left side of the bike rather than the right as you would for setting the timing.
From the left you can see the cam itself where the sprockets attach. See if the casting of the cam is sitting the same for the two cams. One might be rolled a bit different if it is off one tooth.

[Jackbob]

Yes thanks Old Colt - they do in fact taper down a couple of mm, so are 30mm ex GS1000ST.

Re the cam timing - had another think about it - I think all is correct - i was very careful to set the reference marks on the sprockets as per the manual. The pin count was a check. Compression is fine on all pots.

Thanks.

[rapidray]

On an 8 valve engine, the valve to valve issue is more dangerous than valve to piston with the cam timing wrong. Just so you know. Ray.