GS1000S Project Bike - Motorcyclist magazine

[Guest]

Hi Folks

I'm in the process of building a semi-custom GS1000S project bike for my personal collection (and the pages of Motorcyclist), and wanted to ask some technical questions re: bore size and piston type.

First off, the bike is not going to be a racer, or a serious hot-rod sort of thing. Just a really well-finished S-model with a custom repaint (stock colors and striping, just a lot better), and blacked-out wheels, fork and engine. It'll look a lot like Larry Pearson's S-model (see pic attached), which has appeared in a few different magazines over the years.

Anyway, I'm not sure what to do with the engine, which is about to be rebuilt from the bottom-end up. Obviously, it'll get fresh pistons and rings, a rebore, a nice, 5-angle valve job and a check of the bottom end. The question is, do I leave it basically stock and just freshen it up, or do an overbore with aftermarket pistons, etc.? It's fast enough as-is, but a little more displacement, and a bit more midrange and top end power, can't hurt. The thing is, I want it to be reliable, and idle, and not be finicky. I may even use stock CV carbs. (It's an '80 model.)

For those who've built 8-valve GS engines, what sort of luck have you had with varying displacements? How about piston type and manufacturer? I've got a Yoshimura exhaust already, and I pretty much plan on using stock CVs with (probably) individual K&Ns mounted.
Thoughts? Thanks much.

Mitch Boehm

GS1000S.jpg

[Nessism]

Wiseco makes a good kit. They make both 73mm and 73.5 mm pistons. I believe the smaller pistons are prefered for durability. You would be advised to use premium fuel with the kit, whereas stock lives nicely on regular. Suzuki still sells stock rings too, so if your cylinder liners are still in good condition it's hard to fault stock if you aren't going to be racing.

One major upgrade that I would strongly suggest is a heavy duty clutch hub backing plate and springs. I've got one in my 1000S and it's a transformal improvement.

[John Kat]

Hi Mitch,
I've read many of your articles over the years!
Great reading for sure.
Welcome to the GS world.
If you have to refresh the engine, the 1085 Wiseko kit works fine.
I've fitted this kit on one of my GS's but I'm not sure it makes much more power than my other GS 1000 (a GS 1000 ST) that came std with special cams and VM 30 carbs?
Beware that fitting pods can be a nightmare to get the setting spot on.
My GS 1085 has CV carbs with pods and I believe I'm only at 95% of perfection after much tuning.
What works nicely is fitting GSXR 1100 first gen wheels, brakes and fork on the GS 1000.
Here's a picture:

[Kiwi Canuck]

Mitch, when I rebuilt my GS1000S I stayed with stock OEM parts and the power is pretty good, seems to match the rest of the chassis, any more power and you may need to start changing suspension parts as well.

I also retained the stock air box as I wanted to make sure I wasn't fussing with it all the time, as I've heard they can be tough to get running right with anything but the stock air box..

I look forward to seeing your progress, hopefully you start a rebuild thread and let us follow along, I did and it was a very rewarding thing to do.

http://www.thegsresources.com/_forum/showthread.php?209217-1980-GS1000S-Reluctant-Rebuild

Here's my two.

[sharpy]

We are not worthy of such experience. Was just reading the changing of the guards this morning and how you trained ure troops way back in 93. Just as John Kat said some 1085 pistons running good fuel is a nice option. Dare i say some 1988 GSXR1100 wheels be a good alternative. Getting rare and mite be rarer after the article. Few pics included for your viewing and welcome.....

[Deadhead184]

Thanks, guys, for the info, and the Last Page blast from the past. (Seems like yesterday I became Editor of Motorcyclist, although it was - amazingly - 22 years ago!)

The more I think about this, the more I may use the stock airbox, which may lead me in a mild direction with the overbore... stock slugs or something just a little bigger. All four GS1000s I've owned (all S-models) have carbureted so nicely, and I don't want to lose that, or reliability. The idea of an ongoing thread on the project sounds good, too, as I'll be chronicling things for the magazine anyway. Here's a photo of the bike from a few years ago...

Again, thanks much, guys and gals

Mitch

IMG_3362.jpg

[RichDesmond]

Mitch,

I forget what year exactly, but Joe Minton did a hop-up article on the GS1000 motor in Motorcyclist. Early '80's I would guess. Lot's of good info in it.
I'm fuzzy on a lot of the details, but I do remember an overbore (I think to 1100cc) and 29mm Mikuni smoothbores.

[dorkburger]

Mitch! Holy smokes..... I cant offer any advice, but its so cool to see you on the GSR! Yours was my favorite era of Motorcyclist. Looking forward to seeing the project. If I recall, I remember your occasional mention of your S and a picture or two of it.

[azr]

Very cool to have yet another member with so much background and experience, welcome to the nut house With my own 78' 1000, it's a stock engine with 29mm smoothbores and K&N's. She dialed in pretty good and goes like a bat out of hell. Once you start messing around with the bores you'll have to spend some serious time with the carbs, but I'm pretty sure you know a 'few' people that could help. Looking forward to the build thread and ultimately the article.

[Charlie G]

Welcome and nice to have you aboard!

[theDoktor]

Mitch, I've got a copy of the original Motorcyclist article that I can scan and send to you. (Anybody else interested?) I built one of these many years ago and am just starting a refresh. Many of the parts the article mentioned are no longer available- the 29mm smoothbores (which I have), the Lockhart Competition oil cooler (which allows the use of braided steel lines & AN fittings- have that too), the Yosh 1085 pistons (higher compression than the Weisco's), and a few other bits. Mine has a Mac 4-2-1 exhaust & stock, degreed cams. My Weisco pistons have a plasma coating on the tops and an anti-friction coating on the skirts. Chassis has Olins shocks and Pirelli Sport Demon tires. Need to install the saltymonk front brake upgrade with the refresh.
Here's what she looked like when I did the original build.78 GS1000- original build.jpg

Let me know if I can help. If interested, I've got a head & cylinder that is from a late model GS1000 with the CV carbs (the large port head) that I'd be willing to part with.

[mustangflyr]

Welcome aboard Mitch, you've been busy since we met at RIH some time ago. I too had a 1980 1000S, mine was stock inside but had 33mm smooth bore carbs, a 700 Lockhart oil cooler, the green coils, K&N filter in the stock no lid air cleaner and a kerker header. The thing was much faster than the 1980 1000E I've had since new that you saw. Not a radical package that "S" but powerful and reliable.

[boyd40]

Hi Mitch,
Good to have you on the GSR page. I am also starting a GS100S restoration/restomod so I will be interested to follow along. I figure that the GS project is easier on the old bones than vintage MX!

Doktor,
I would love to get a copy of the article you mentioned.


Wayne Boyd

[stoprunner]

Hi Mitch,

Years of Motorcyclist for me too, Can you share info about anybody that can help with an GS engine rebuild in the LA aerea?, I'm in the middle of bringing back to life a 78 GS1000 and the engine is next.

TheDoctor I'm interested too in the art.

Miguel Galluzzi

[theDoktor]

GS1000 Hop-Up article from Motorcyclist December, 1984

Guys here's the article I mentioned. Hopefully I haven't violated any copyright laws!

My version of the hop-up, as I mentioned earlier, has Weisco 1085 pistons rather than the no longer available Yoshimura pistons, degreed stock cams, a Mac 4-2-1 exhaust rather than the V&H unit, the 29mm smoothbores, (going back to the) stock airbox with a K&N filter rather than the pods currently installed, Dyna S ignition & coils, and the Lockhart Competition cooler, also no longer available for this application. The chassis has the Progressive springs (about to be changed to Sonic springs- Rich at Sonic knows his stuff!), Weigl fork brace, SuperBike bars, all braided stainless steel brake lines and Ohlins shocks rather than the Marzocchi shocks, and Pirelli Sport Demon tires.
Of note, the only part that makes the Lockhart Competition cooler or any other cooler that uses braided stainless cooler lines no longer available for this bike is the oil pressure cover that was made for this application to attach the AN fittings for the oil lines. This could be copied and re-made by someone with the appropriate machine tools.