A modern fork upgrade for 17,18 and 19" wheels

[salty_monk]

Seems like a wasted opportunity to use stock brakes there John... I guess if yours were in good shape & the machining is not expensive then why not.

[John Kat]

Hi Salty, the OEM brakes are obviously not in the same class as what can found on modern bikes today.
On the other hand the calipers that go with the slotted disks that appeared on the 1980 models are a big improvement over the previous generation.
That combined with modern pads that are properly bed-in give you appreciable stopping power at least in my view.
The purpose of the exercise was not to upgrade every part of the GS 1000 but only the front fork as I'm convinced that it's the weakest link on the bike.
Doing so, will also allow me to keep the bike relatively standard
If the next weakest link is the braking power, I will follow your example and go for the CBR disks and Kawasaki calipers
I'm still missing a few parts to complete the set-up but I'm eager to test it on the road, specially that with my extended GSXR fork, I will be able to try different ride heights with the corresponding changes in trail and rake
PS: if you'd like to produce the required parts for the GSR community, I'd be glad to provide you my drawings

[althomas101]

Why did you extend the forks if you are going to have 3 inches sticking out of the top tree? You do know that is a hazard on a get off.

[John Kat]

Why did you extend the forks if you are going to have 3 inches sticking out of the top tree? You do know that is a hazard on a get off.

I extended the fork for a previous project when I was using 17" wheels on my GS 1000 XP.
With the 19" wheels, I should be able to do without the fork extensions but I won't take them off until I do a back to back test between the two wheel sizes
I agree that it's dangerous to have the tubes protude above the triples...but it's even more dangerous to run out off ground clearance
Here's what the ground clearance looked like with the 17" wheels.

[althomas101]

I figured you had your reasons, I just wanted to know them. Thanks for the reply, I can see myself upgrading suspension down the road so this is of particular interest to me.

[posplayr]

Hi Salty, the OEM brakes are obviously not in the same class as what can found on modern bikes today.
On the other hand the calipers that go with the slotted disks that appeared on the 1980 models are a big improvement over the previous generation.
That combined with modern pads that are properly bed-in give you appreciable stopping power at least in my view.
The purpose of the exercise was not to upgrade every part of the GS 1000 but only the front fork as I'm convinced that it's the weakest link on the bike.
Doing so, will also allow me to keep the bike relatively standard
If the next weakest link is the braking power, I will follow your example and go for the CBR disks and Kawasaki calipers
I'm still missing a few parts to complete the set-up but I'm eager to test it on the road, specially that with my extended GSXR fork, I will be able to try different ride heights with the corresponding changes in trail and rake
PS: if you'd like to produce the required parts for the GSR community, I'd be glad to provide you my drawings

John,
Well you will have to give us all a full road test report. I first upgraded my ED as much as possible(fork brace,sintered brake pads, cartridge emulators, fork springs, Ohlins rear, sticky sport demon tires) using all stock wheel,tires,forks and brakes. And the bikes handled well but there was a definite limit and road handling feel would fall off as speeds exceeded 70-80 mph. With the latest engine upgrades of an 1166 kit it only mad it worse.

My next step was rather large as I went to GSXR 88 wheels/brakes/forks(41mm), and fit 110/80-18 and 170/60-18 tires with it.
So it is hard to segregate the effects, but I would think that the tires and wheels have the most effect certainly as speeds rise. To a certain extent it is academic to me, but still of interest to hear your conclusions given you can compare your own bikes with radial and stock forks with this one with the B-12 forks.

Jim

[John Kat]

John,
Well you will have to give us all a full road test report. I first upgraded my ED as much as possible(fork brace,sintered brake pads, cartridge emulators, fork springs, Ohlins rear, sticky sport demon tires) using all stock wheel,tires,forks and brakes. And the bikes handled well but there was a definite limit and road handling feel would fall off as speeds exceeded 70-80 mph. With the latest engine upgrades of an 1166 kit it only mad it worse.

My next step was rather large as I went to GSXR 88 wheels/brakes/forks(41mm), and fit 110/80-18 and 170/60-18 tires with it.
So it is hard to segregate the effects, but I would think that the tires and wheels have the most effect certainly as speeds rise. To a certain extent it is academic to me, but still of interest to hear your conclusions given you can compare your own bikes with radial and stock forks with this one with the B-12 forks.

Jim

Jim, I will definitely provide feedback following the road test
My experience so far has been with my GS 1000 XP, a GS 1000 with GSXR 1100 K components including 43 mm RSU forks, 17" wheels, brakes and even a single shock swingarm.
To me it was one of the best motorcycle experiences I've had in my life
My experience correlates your findings: no vagueness in the steering at speeds above 70 to 80 mph!
Later on to lighten the bike, I modified my GS 1000 XP with GSXR 1100 G/H components like you did with 18" wheels, brakes and front fork.
After lots of adjustments on the front fork with oil viscosity, spring rates and RaceTech cartridges the bike runs fine but...not quite as good as what I remember it was with the GSXR K components???
It's great fun for sure but I'm not sure the magic is still there allthough the bike is definitely lighter than before.
Does the magic come from the 17" wheels ( and tires), the cartridge type fork or a subtle change in geometry or in riding position, I don't know yet but this new experiment should help clarify the situation.
Wait and see

[John Kat]

I secured the front mudguard today with 40 mm spacers
Going from a 17" wheel to a 19" wheel doesn't only add 1" to the radius given the aspect ratio of the 19" tires!
It's almost garanteed now that I will not need the extended fork.
It's not the final design but here's what it looks like.
Next the fork lock stops and I'm underway

[slayer61]

Keep it up John... We are all watching you!

[John Kat]

And the result is
Today I managed to pull the last parts together and went for a ride on the bike.
The best way to describe how it feels is "One Block"
Gone is the kind of twitchiness(?) as the bike went over small bumps that usually unsettled the steering.
Going faster you are in total control and at no time you think "that's fast enough".
In fact my GS 1000 ST was the bike I liked the least in my stable.
It was fast enough and it was fun but only up to a certain speed.
Beyond that you clearly felt in dangerous territory.
Of course, you can feel that you are running on cross ply tires but the pleasure is there.
I can't help comparing with my GS 1000 XP equipped with 1st gen GSXR components.
Again here the front fork is way superior to the previous model despite the "gold valve" and endless tuning with different oil viscosities and springs
It's very strange, when you pump the front suspension up and down with the cartridge type fork you get the feeling it's way too stiff compared to the 1st gen fork but when you ride the bike you feel the front wheel is under control and it's still comfortable?
In summary, I would say that the BEST upgrade for a GS 1000 is a cartridge type fork
As a side note, I will not upgrade the brakes...but I will put some better shocks at the rear
Here's the bike " as tested"

[posplayr]

very nice and well done. These are 43 mm cartridge forks? What year Bandit works? Can you summarize the changes required for the forks? Axles, bearings, brake adapters, handle bars?

[John Kat]

very nice and well done. These are 43 mm cartridge forks? What year Bandit works? Can you summarize the changes required for the forks? Axles, bearings, brake adapters, handle bars?

Thanks Jim
For this conversion you need:
GSXR 1100 K ( 1989) Triple trees top and bottom
Eitheir GSXR 1100 K RSU 43 mm fork legs if you run with a conventional handlebar.
In this case you will need an LSL or ABM adapter to take the handlebar.
Or Bandit 1200 phase 1 ( until 1999 I believe) RSU 43 mm fork legs.
As these legs are longer, you can use clip-ons ( ABM in my case) that go on top of the triple tree.
The triple tree bearings are the original ones.
You will have to use the knurled nut from the gs 1000 under the top triple.
The wheel axle is eitheir the original one or better the GSXR 1100 G/H 15 mm one that's a little longer.
I also used some shims to center the wheel.
The mudguard comes from a GSXR 1100 J ( 1988)
The headlight brackets came from a local "supermarket"
On the machining side you need the:
The wheel axle adapters
The lock stops
The caliper brackets
The stand-offs for the mudguard
This must of cost me 300$ but there was a lot of going back and forth.
If you are interested, I will PM you my drawings?

[jwhelan65]

John,

This is great info, I think the only thing I would have done differently being that far into it is upgrade the calipers as Dan mentioned. Aside from that a fantastic job that warrants a sticky thread. Your work always draws a crowd.

[John Kat]

John,

This is great info, I think the only thing I would have done differently being that far into it is upgrade the calipers as Dan mentioned. Aside from that a fantastic job that warrants a sticky thread. Your work always draws a crowd.

Thanks Jwhelan
One day maybe, I'll get to your quality level!
By the way, I saw Pazzo levers on your GS 1100 but what brackets do they fit on?

[jwhelan65]

Thanks Jwhelan
One day maybe, I'll get to your quality level!
By the way, I saw Pazzo levers on your GS 1100 but what brackets do they fit on?

Both the clutch perch and front master cylinder came from a 2011 Yamaha FZ8. Once you have them in place you can order just about any after market lever you want. They also have normal upright mirror mounts. This allows for all the fancy modern day bling.