Suzuki RG500 GAMMA

Contribution byBob Truelson

Subject: Gamma fork graft (1)-repeat

Part 1 : Fitment (Part 2 later - how do they work)

Hardware:
Slightly used fork kit-
1 - set of gold anodized USD Yosh/KYB (were on a GSXR '86 LTD)
 (note: Stock GSXR 1100's come with something very similar to these although 
Yosh. valving and triple clamps are different , and according to Lindemann 
Eng., mine have more aluminum parts which make them lighter - I'm not so sure 
about this)
1 - Axle (hollow stainless, 20 mm outside diam, - the RG's is 15mm solid)
1 - Fibreglass fender (well made, but doesn't extend much out back)
      I'll probably use this a mold for a carbon fibre piece next winter
1 - Set of black anodized triple clamps
    good quality with Yosh emblem engraved
1 - Set of clip-ons for 52 mm fork tubes (most of the tube is actually 56mm)
    cheesy quality, steel, with too much downward angle on the bars 
    
Slightly used front brake system (came with forks)
  note: this is basically the same system as you would find on a gixxer 
1100 of a few years ago) 
 1 - Set of 310 mm, 4.5 thickness full-floatingrotors
1 - Set of Nissin 4 piston calipers
1 - Set of steel brake lines
1 - Nissin 2 Master cylinder with remote reservoir and adjustable lever

The Good, the Bad, and the Trade-off's of installation:
Having bought the above items at arms length, sight unseen, I was 
understandaby a bit nervous about many things, some obvious ones like weight, 
fitment to the steering head  etc., and of course the unexpected.

The weight was easy to check.  I weighted all the stock front end stuff that 
was being totally replaced (even though some had been replaced earlier).  And 
I weighted all the replacement bits I would have in place (those now include 
17" Marvic wheel, all brake components, forks and triple clamps, fender, 
axle).  According to my certified bathroom scales I have just hung 10 pounds 
off my front end - yikes. 

The steering head question. Anxiety big-time. Pull off the stocker - easy.  
The big roller bearing in the bottom stays on the shaft, and the 
smaller top roller unit stays in place.  Yeh, like I'll just be able to slide 
the Yosh unit with its tapered bearing right in huh?  Push, slide, clunk.
IT FIT PERFECTLY BOTH ENDS. THERE IS A GOD AND HE LIKES RG'S!

Wow, in five minutes I've got the clamps in, another couple to slide the 
tubes in, and... there they sit, USD already installed and ready to go?...NOT.
If I picked the back end up and pointed my way out of the garage, I would 
have got at least to the first corner.  
Those massive tubes, with a much wider lateral spread than the stockers, of 
course weren't designed to live in the confines of the RG front end 
externals.  They immediately contact the brackets that hold the front 
signals.  Since I built mine in years ago the pockets they were designed for 
anyway, this first obstacle was a simple hacksaw/grind solution.  Then they 
hit things like the rectifier;that and the horn had to be moved slightly.  
Hmm, so far so good, I've got not bad movement now. 
Unsuspecting, I bolt up the clip-ons. Bummer.  They hang so low they hit 
the fairing top edges.  Also, the forks aren't tall enough to allow clip-
ons to be raised much and still have room for the top triple clamp to still 
fit on the shaft.  Partial solution was to toss the clip-ons and buy a set 
of Spondon units I found locally(which I had to have bored to 52 mm).  They 
have an angle somewhere between stock and the KYB's, and are much better 
quality gold anodized.  I suppose adjustable Chafong's or whaterver would be 
better but I didn't want to delay.  Now time to bolt on the levers and 
such.  More depression.  All of this stuff, of course, now wants to contact 
the front fairing protrusions, instruments, etc. well before the amount of 
bar movement you want.  
What followed in the past weeks I won't detail or bore you with.  Suffice to 
say I scrounged, and hacked and ground and moved  to achieve mere fractions 
of an inch here and fractions there to get some semblance of side to side 
movement that would be acceptable.  For example, the instrument cluster had 
to raised and pushed ahead as far as it would go, with a lot of help.  
Your best friend through this is a rotary grinder with flex shaft. 

And then there was the rest of the front end down below:
The calipers were made for the forks and 310 mm rotors so that was a plus.
The wheel bearings had to be replaced with 20mm inside diam. units, I made 
up a new spacer that fits between the bearings to provide proper loading, I 
had to find a GSXR speedo driver with 20mm inside diam (and of course that 
just doesn't slip on - more grinding), I had to drill new mounting holes 
in the rotors to fit the Marvic which was the same as the stock RG, the 
rotors had to be shimmed out to fit the placement of the calipers (shim 
material came with the kit), Once all that is settled you have to make up 
axle spacers on each side to exactly centre the wheel and the rotors 
(spacer material also came with the kit).    Long live the dial caliper.

There was probably more, but that's the jist.

My first Sunday ride (planned yesterday) was rained out, though I did get a 
trial run in to work last Fri.

Stay tuned for Part 2, and scans, later.

Bob T./RG  

From: "Truelson, Bob" 
Subject: Gamma Fork Graft ( 2)-repeat



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FORWARDED FROM: Truelson, Bob
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Following on the GFG Part 1 of May 31/94.....

Gamma Fork Graft - Part 2; How they work 

Finally scored some clear Sunday morning weather to put my USD Yosh/Kayaba 
forks through the paces, but first.......
Pre-ride #1 
As with any modification, I have found that the first ride out of the garage 
is more telling than anything else, to compare what you started with 
beforehand.  You quickly get used to the new and forget exactly what the 
original felt like.  Unless of course, you're like some of the guys on the 
net who just take out one of their other RGs.
So my first impression down my rather rough street was 'who smoothed out 
the road'?  :-)     _Noticeable_ difference in springing and damping control 
with the effect that the road felt about 50% smoother.  I guess that is what 
good forks are all about.  My fear was that with the stiffer feel of the 
front, and that the previous application of the forks was on a 750, that I 
could be in store for a buckboard ride in their existing state.  Wasn't 
expecting plush.
One interesting thing though (which made sense when I thought about it later) 
was that  I didn't recall the back end feeling that choppy before.  The 
increased forward cant with the lower clip-ons, and the extra 10 pounds up 
front, and the Fox shock now had too much spring preload and damping.

Pre-ride #2 (rain)

Being a fair-weather biker, and having external foam filters, wet-weather 
riding is out of the picture.  However, I had gambled and lost.
As I mentioned during installation, the new clip-ons are substantially lower 
than stockers and feel about the same as any race-oriented 750, for example.  
As I trundelled along in the wet I became increasing bothered by the hand 
fatigue and numbness after what seemed like short periods.

Sunday's Ride

Continuing the above thread, what I didn't take into account was that 
during 'normal' riding, using the front brake often, hand fatigue doesn't 
develop (when you live in the twisties of course).  The new lower riding 
position, in context with a lower-than-stock rear glass seat, felt 
_excellent_ and completely natural.
To compensate for the lighter weight of the RG (~365 pounds wet) compared to 
the superbike the forks came off (390 pounds wet) I backed off the spring 
preload all the way.  Also, the previous owner had already taken off 2cm of 
each spacer.  Front sack was now a measured 11/4 inchs.  Various sources 
say you should have between 15 and 30% of your maximum travel represented by 
sack.  Having placed a tie around the fork leg prior to the ride and not 
purposely hitting a hidden teeth-jarring ledge in a road at speed, has 
indicated the forks have a travel of about 4 inches or 100 mm.  I think my 
preload is close but could be tightened up slightly. Fork oil is 7.5wt but 
Yosh U.S.A. says 5 wt might be even better.
Without experimenting with damping adjustments on this day (set at 7 out of 9 
softest for compression, and 5 out of 17 for rebound) I was very impressed 
with their overall composure.  The sure-footedness and recovery over 
rough spots was much better than my old forks.  Although some of the former 
likely was due simply to the increased weight over the front tire.
Cornering confidence was 
improved, and as Keith Code likes to preach, having more attention available 
now for other things is a bonus.  I found that, subconsciously, I was 
programmed to react a certain way to a certain level of road condition (ie. a 
really firm grasp on the bars for the nasty stuff).  For the first while I 
was continually feeding this 'input' in from memory on a very familiar road 
and was soon finding that the bike didn't need it.  It was actually fun to 
pitch the bike into the rough and just let it do the work, while you 
take a more relaxed grip. Within reason of course.  In one careless moment , I
combined a corner, bumps, loose grip, and a clutchless upshift and got 
rewarded with the start of a tank-slapper.   Once those heavy legs start 
to wag, hang on.  I still swear by a good steering damper (which I had 
purposely turned off) when liable to encounter bumps in fast corners - where 
your riding style may not allow good firm leveridge on the bars.  
Operator error accepted, the forks tracked well over a variety of surfaces 
and at speed to 240km without the damper on.  Braking into corners 
was uneventful and no flexing from hard braking was noticeable.  The front 
does feel somewhat heavier but not at the expense of that flickability 
gammas are known for.  The planted feel is the big payoff.  
In summary, I have no regrets and only accolades for these forks, even though 
they might be overkill.  While I don't have many benchmarks to compare, the 
closest in recent memory was to riding my friends RC30, which had wonderful 
compliance (he saw the light a while back when he sold the RC, bought an RG;
 last week he found some new KYB's gathering dust at a shop and has 
ordered adjustable triple clamps from Kosman).

Brakes,
This is getting too long, so suffice to say that the Nissin set-up with 310 
rotors works as expected - hang onto the bars tight or get launched over 
them.  I'm sure if I had put these on the RG by themselves, the stock legs 
would have flexed their hearts out (like my old Ninja 600 used to do 
normally).  I should qualify this by saying that my old RG brakes were 
getting tired and the eight year old rubber lines were no longer able to feed 
the power and crispness they once did.  

What's next? (the sign of a true addict)
Dunno, what about that beam frame deal Rob K.?

Bob T./RG

Rob Koopman ( Rob.Koopman@inter.NL.net ) ^{RG500 Index}