More modern cartridge fork options - retaining GS wheels & proper/revised geometry

[Suzukian]

I've always thought about trying to do something about my 1983 GS750ES, I purchased the bike new. To be honest, the bike does everything I need it to do. It is very forgiving in turns, and will get out our of trouble, just as fast as you got yourself into it. The only thing that ever scraped was the center stand. I am one of the few people who find the anti-dive front end useful. I don't have any idea what other front ends people have put on these bikes. The only reason the question comes up is front tires for this bike are very limited. The ones I can get have been great, but I would hate to get to a point where it becomes impossible. If anyone could link me to an "Idiot's Guide" to this particular bike front end conversions, I would be most appreciative. I do have a small machine shop, and can do much machining, and also have a Mig and Tig welder. What I don't have is the information, and I get lost quick with that. I saw a conversion to a 17" front rim, but no info was posted one what parts he used. Thank You.

 

[John Kat]

In terms of tires, have you tried the Conti Classic Attack that are radial tires ?
I've fitted them on my GS 1000 ST that would always go into a weave at high speed due to it's very narrow rear 18" wheel.
With the Conti's its all gone!
Continental Motorcycle Tires ContiClassicAttack (continental-tires.com)​
Are these available in the USA is the question?
For the front fork conversion, the first question to ask is what is your goal?
For instance, a major improvement came when the manufacturers dicovered "Cartrigde Forks" that replaced "Damping Rod" forks.
This will immediately bring your bike in the "modern day" world.
Candidates here are the GSXR 1100 K, the Bandit 1200 and Yamaha R6 all 43 mm diameter RSU models.
The GSXR G/H have the older design and I guess that most of the 41 mm forks are similarly outdated.
Next comes the length of the stantions.
For the GS 1000 the GSXR 11 K are too short, the Bandit 1200's work fine on the 1100 Katana but could be too long for the GS 1000?
The Yamaha R6 are both light, fully adjustable and the right length.
The stantions will fit in both GSXR 11K triples and of course R6 triples as they share the same spread between the stantions.
The GSXR 11K triples have the advantage of making it easier to fit the lock stops on the lower triple while you need to weld a piece of metal on the the GS frame to do so.
All Balls racing have the bearings for all of these upgrades.
Good luck!

PS: Bear in mind that these upgrades will use 17" front wheels with a tire width of 120 mm. This will require an upgraded wider 160 mm tire on the rear wheel!

 

[Suzukian]

I think I'll leave it stock. I have a ZZR1200 I am putting much attention into. Having purchased the Suzuki GS750ES new kind of makes me want to keep it that way. If I have too change out two rims, and forks, etc., it won't be the same bike, and that bike still out handles many of the more modern bikes I have rive. I know the right person could really improve it,,, but I would have to have an idiot's guide. I could do any machining necessary, but knowing what to do, well, I know my limitations. I figured if someone had a link to a page with that kind of information, it would be great to study, then make a decision. ;

 

[salty_monk]

You could read my GS750ES thread. That had a GSXR1100 front end & a 5.5 rear wheel, a ducati Shock and some other minor mods.....

 

[Suzukian]

I sent you a P.M.. I haves searched but cannot find that thread?

 

[Suzukian]

I decided to slap on a virtually new GS1150 complete front end I got for my '83 GS750ES that looks new, and was really cheap. I am mounting 3 spoke GSXR 600 rims, both 17", that I got ridiculously cheap, just have to paint them a civilized color. This year wheels has the speedo drive, so that will save some aggravation.

I have a TOKICO Dual Pot braking system that should bolt right up, a couple of washers to center them inwards. I was wondering about fork improvements for this bike now different fork set up (GS1150), any ideas?

p.s. I still have to get the ZZR1200 ready to ride (steel braided lines, NISSIN calipers, quick oil change release valves), I won't touch the GS until the ZZR is up and running, very minor things left, but it's 28 degrees in my Barn!!

 

[Chuck78]

In terms of tires, have you tried the Conti Classic Attack that are radial tires ?
I've fitted them on my GS 1000 ST that would always go into a weave at high speed due to it's very narrow rear 18" wheel.
With the Conti's its all gone!
Continental Motorcycle Tires ContiClassicAttack (continental-tires.com)​
Are these available in the USA is the question?

Good advice John...

I just wanted to add that I've been running Continental Road Attack 3 tires on my big bore GS750 for a couple seasons now, and I'd be reluctant to switch back to anything else... They resolved the same issue for me, lowering the front end and raising the rear end to get quicker steering gave me a bit of head shake if I would take my hands off of the handlebars at certain speeds. Different shock heights or different front tire sizes would change the speed at which I would get this wobble. Continentals completely eliminated that as they are radials of the highest quality. I was skeptical at first that anything could grip better than Shinko or Pirelli Sport Demon bias ply tires, as that grip is pretty phenomenal especially for the price. The Continentals cost significantly more but I get significantly more miles out of them and they grip phenomenally well. No reason to ever run an Avon Road Rider to get more miles, I've had those tires scare me a few times during hard cornering despite so many people swearing by them, the grip was not good enough for me on the Avon street tires... The Continentals on the other hand are amazing.

I've got some CBR600F4 forks here for a big bore GS400 build I've been sitting on for a while, as well as some RF900R forks for a Rickman CR road race frame that I'm finally going to get professionally repaired & build up with a GS1000 engine this winter.
I've got far too many bikes currently, and have been contemplating selling my main bike this whole time, my GS750 big bore, in favor of keeping the GS400 & 425, GS550/740cc, & GS1000 + Rickman framed GS 1000/1135cc... Plus 4 2-stroke dirt bikes in the stable, running out of room!

 

[John Kat]

Good advice John...

I just wanted to add that I've been running Continental Road Attack 3 tires on my big bore GS750 for a couple seasons now, and I'd be reluctant to switch back to anything else... They resolved the same issue for me, lowering the front end and raising the rear end to get quicker steering gave me a bit of head shake if I would take my hands off of the handlebars at certain speeds. Different shock heights or different front tire sizes would change the speed at which I would get this wobble. Continentals completely eliminated that as they are radials of the highest quality. I was skeptical at first that anything could grip better than Shinko or Pirelli Sport Demon bias ply tires, as that grip is pretty phenomenal especially for the price. The Continentals cost significantly more but I get significantly more miles out of them and they grip phenomenally well. No reason to ever run an Avon Road Rider to get more miles, I've had those tires scare me a few times during hard cornering despite so many people swearing by them, the grip was not good enough for me on the Avon street tires... The Continentals on the other hand are amazing.

I've got some CBR600F4 forks here for a big bore GS400 build I've been sitting on for a while, as well as some RF900R forks for a Rickman CR road race frame that I'm finally going to get professionally repaired & build up with a GS1000 engine this winter.
I've got far too many bikes currently, and have been contemplating selling my main bike this whole time, my GS750 big bore, in favor of keeping the GS400 & 425, GS550/740cc, & GS1000 + Rickman framed GS 1000/1135cc... Plus 4 2-stroke dirt bikes in the stable, running out of room!

Hi Chuck,

I'm glad to read that you have the same experience with the Conti Road Attack as I have.
The other day, I raced with a Honda VFR 750 on some fast winding roads and I would only loose a meter or two in corner entries mainly due to the heft of my GS 1000ST.
I'm currently finishing a GS 1000 with a GS 1150 engine fitted with a1230 Wiseco kit.
This one has GSXR 1100 suspension and wheels.
It's difficult to stop modifying bikes...

 

[Chuck78]

...and I would only loose a meter or two in corner entries mainly due to the heft of my GS 1000ST.



It's difficult to stop modifying bikes...

This is exactly why I am considering doing more extensive work to my GS550 with 650 top end/740cc pistons...
The weight of my big bore 750 or my 1,000 are only the secondary reason I'm considering making the big bore 550 my primary bike. The primary reason is because of the old air-cooled Big 4 cylinder engines' width being very prohibitive to substantial lean angles... The stator cover is just too wide! Cutting a 45? slice out of the bottom corner as much as possible without interfering with the stator, and welding in a plate, is only a bit of help.

I'm contemplating putting some RS 34 carbs onto the 550/650-740cc, although it's set up very nicely for some VM 29 smooth bores or CR 29 smooth bores.

I think an aftermarket camshaft & those carbs with the more advanced closed chamber head and matching pistons will really yield great results.
The weight of my 750 doesn't bother me when I'm riding it fast in the twisties so much, but when I jump on my buddy's 610cc GS550 with NLA Wiseco K610 pistons, I absolutely notice a difference in the effort required to toss it left and right and lean it into corners. Which is also why I've been infatuated for several years with building up my GS 425 as a ported head big cam big carb track day and twisties bike. Instead I now have gathered a free GS400 frame which I got titled, and several 400 and 425 engines as well as crates of parts plenty enough to build a complete bike, including lots of go fast parts like GS1000/750 Wheels with aftermarket rims, aluminum swing arm, CBR 600 F4 forks, aftermarket exhausts, Fox Factory Shox, etc...

 

[John Kat]

I can't agree more, the weight is the N?1 problem on these GS 1000's.
Its possible to drastically reduce the weight with GSXR 1100 86/87 wheels and suspension which I did on one of my bikes but the ultimate weight saving goes with a GSXR 1052 engine in the GS 1000 frame with a Yamaha R6 complete front end. Here's what it looks like:

 

[salty_monk]

Looking good as ever John! Happy New Year!

 

[John Kat]

Looking good as ever John! Happy New Year!

Thanks Salty! I forgot to mention that my OEM GS 1000 ST does have your front brake kit. It makes a HUGE difference for sure.
Happy New Year to you to!

 

[slayer61]

I used 1100K forks & triples on my ES. It sits about 3/4" lower in the front, but I have the rear a little higher ala Nori Haga to make up for it!

ETA it uses an 18" front wheel rather than the factory 17 from the GSXR

 

[Chuck78]

I can't agree more, the weight is the N?1 problem on these GS 1000's.
Its possible to drastically reduce the weight with GSXR 1100 86/87 wheels and suspension which I did on one of my bikes but the ultimate weight saving goes with a GSXR 1052 engine in the GS 1000 frame with a Yamaha R6 complete front end. Here's what it looks like:

John, that bike is stunning! The only way I'd run modern wheels like that though is if I were to run some with polished aluminum rims and blacked out mag wheel spokes, although I still really think the vintage chassis needs the taller 18" tires and aftermarket rearsets to have a performance amount of cornering clearance... And I'm a real sucker for wire spoke wheels....
Those Yamaha R6 forks are the lightest of the 43mm (and 41mm) cartridge forks I was browsing when I started this cartridge fork upgrade quest...

So what year of engine is that GSXR1000? Is a Bandit 1200 variant of the old oil cooled GSXR1000/1100 engines going to be much taller than the air/oil cooled GSXR1000 engines? Although I have a multitude of GS1000 engines and spares and 1100G D-Port heads, 2 welded crankshafts (1 being a GS1000 stroker crankshaft built from GS1100E + GS1100G crank parts), one of those hot rod engines really would be the ultimate answer in terms of air cooled performance big bores, as they are NARROWER!!! More cornering clearance is the big issue. I'll do some more mods to my 740cc GS550/650 project with some RS34's and head porting, and get the chassis dialed in, and then see if I still desire more displacement... The 1977 Rickman chassis might be out of place with a 1989 or early 1990's air/oil cooled Bandit/GSXR engine vs a GS1000 engine that would make it worth more being period correct, and also allow it to fit into vintage racing classes... It's tempting though. My GS750 might go really well with a GSXR1000 engine!

What exhaust did you end up using with your 78-79 GS1000 chassis + 1989-ish GSXR1000 air cooled engine?