Suzuki RG500 GAMMA

RG 500 Gamma Project:
Chassis:
Tecnomagnesio Vortice Rims: 3.5x17 Front, 5.5x17 Rear
Michelin Macadam Radials - A90X 120/70ZR-17 Front,  M90X 170/60ZR-17 Rear
Brembo 300mm Floating Disks, 4 piston calipers, SS lines, 2 piston "micro"
rear caliper - Motul 600 fluid
Race Tech Cartridge Emulators - removed anti dive from forks,  stock fork
springs
Fox Shox with 340# Spring
Braced (underside) swing arm
Ohio Licence plate:  RG500

Power Train:
ENTIRE updated gears in transmission
modified clutch baskets - added oil passages
TC Chambers
30.5mm Bored carbs - Mark Russell - VERY NICE JOB
Matched carb spacers to outer, inner rotor valve covers and matched intake
tract to covers also
5 degree cut rotors
ported & polished cylinders.  Exhaust opened 1.5mm, raised 1mm, all transfers
cleaned up and knife edged webbing between transfers
matched exhaust ports to chambers at header
15 degree 9.15mm wide squish band in heads, .032" squish clearance
.036" cylinder spacers.
Honda HP coolant
Silkoleen tranny fluid
Yamalube R oil
Trying BOTH K&N filters w/trunking (155 main jets)  AND Lance Gamma Uni's
(230 mains)

The whole idea of doing a spacer motor was to increase horsepower for minimal
cost.  By moving the cylinders up, the port timing in relation to the crank
angle is changed.  We (Randy, Rustie and myself) decided to run a spacer
somewhere in the range of .035" thick.  Randy get's the credit for doing the
homework on this part, as he's the one that determined how far to go.  Moving
the cylinder up gives more mid range hp.  An extreme example of such tuning
is the 1996 Yamaha YZ250.  They came with DOGS for engines so Yamaha offered
a kit that consisted of a 10mm!! cylinder spacer and a con rod that was 10mm
longer also.  By moving the port timing in relationship to the crank angle,
the spacer engine came alive over stock and was considered to be one of the
BEST of =9196!

While I had my engine apart, I figured that I would go ahead and do the
"standard" mods also, as one can never have too much HP!  The bored carbs,
ported cylinders and modified rotors should allow higher revs. 

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I started out with a bone stock 1986 Blue/White Canadian RG500.  The thing
was in fairly good shape, with 8K on the speedo and some story about how the
guy down the street from the fellow I bought it from had stolen it.  The only
thing wrong with the bike, other than having a stock - aka broken and falling
off - belly pan, was that all the locks use a different key.  A quick use of
a file and one key does all again.

The first thing I did was to install a set of Lance Uni Filters and ball
valves.  The guy that bought my first RG from me installed a set and said it
made a world of difference.  I was happy with the performance of the filters,
but I did not see a huge increase in anything.  The ball valves worked great.
 No more piddling the tank out on the garage floor if I forgot to turn off
the petcock.

Next, I decided it was time to fiddle with the suspension of the bike.  On my
first RG (bought from Greg Lewis in 1986) I installed a set of Marvic NSR
rims, 3.25 x 17 front and 5.00 x 18 rear.  At the time the only tires I could
find to fit them were racing rain tires!  I also had installed Kossman rotors
and Lockheed calipers.  From this I knew where I wanted to go with my present
RG.

After some searching, I discovered that Technomag and Brembo made wheels and
brakes that bolted directly on the RG.  I had Rick Lance brace the swing arm,
modify the front forks with Race Tech emulators, and purchased a Fox Shox.  I
was absolutely blown away with the handling improvements!!!  I have yet to
ride a motorcycle that is as responsive, yet stable, as my RG with the setup
I'm running.

Obviously, horse power was the next logical thing to install.  Exotic bike,
Killer handling, now it needed to outrun modern 750's!!!

TC pipes were added.  At first I wasn't overly impressed.  I had some strange
jetting problems and had a hard time sorting things out.  The bike had decent
mid range, but would not pull even to redline.  It felt VERY flat.  In the
process of getting it right, I started developing tranny problems.  It would
jump out and back into 2nd - like it had hit a patch of ice, jump out of 4th
and was getting hard to shift.  So, out comes the tranny and the "Long Dry
Summer" began.

I discovered that ALL SIX of the gears on the driven shaft were toast!  The
drive dogs and the receiver holes of the entire set were VERY worn.  I got
lucky and dodged a HUGE bullet on this one.  The other 6 gears were all fine.
 No signs of wear anywhere.  The shift forks were all fine except for a
slight burr on one - which was shaved off with no damage.  My clutch was also
in desperate need of attention.  The nut that holds it onto the drive shaft
was FINGER TIGHT when I removed it!  All the washers, the bearings, inner and
outer baskets and pressure plate were all replaced.  I also modified the
clutch baskets for better oil flow through it.  Oddly enough, the clutch
plates were all in very good shape!  No more "Gamma Rattle" from my clutch
now!

I figured that since I had the bike apart, why not go ahead and see what
could be done.  After much talking with Randy Norian, Bob Truelson and
Rustie, it was decided that the carbs needed boring, the rotors needed
modifying, the heads needed work and I figured that I'd take a stab at
porting.  As the search for HP became deeper, the idea of spacing the jugs
off the cases to change the timing came to light and it was deemed the way to
go.  Fairly easy and cheap to do.  Rustie supplied me with a sheet of .063"
thick aluminum that is made of .003" thick layers.  Base gaskets were copied
and spacers were made.

Bob took care of my carb boring.  Mark Russell did his magic and opened them
up to 30.5mm, decked the tops of the slides and matched everything to the
outer RV covers.  Mark also had a spare set of 5 degree rotors lying around,
so I took them off his hands.  When I receive the carbs & RV covers back,I
matched the case intake tracts to the covers and also countersunk the bolts
in the intake tracts.  The K&N filters work out very nicely.  I spaced the
tank up .200".

I followed Randy's specs on porting, opening the exhaust port 1.5mm by
ovaling the sides and raised them 1.mm.  All the casting crap was removed
from the ports, as well as matching the liners to the jugs, polishing and
cleaning up of the exhaust tract was done also.  I was able to match my
spacer with the cases and the jugs, so the air/fuel mixture flow is as smooth
as possible.

Between Randy and Rustie, we decided on going with a 9.15mm wide 15 degree
squish band.  Rustie cut the bands and then knocked off .075" to get the
squish correct.  I kept getting measurements that were .003" off between the
front and rear and after MUCH scrutiny and careful measurements, it was
discovered that my cases are not equal.  The front cylinders are .003" HIGHER
than the rears.  It has been pointed out to me that the pistons can vary a
touch, but I was able to trace it down to the cases.  My front spacer ended
up being one layer thinner than the rear, bit it all works out in the end
just fine.

The biggest problem has been with the compression readings.  We are looking
for a pressure in the 160 - 165 psi range.  I have had readings from 160 to
210 psi!!!  This depends on what cylinder and what gauge (calibrated) I've
checked.  Stock Gamma heads are CAST and the combustion domes are NOT EQUAL!!
 Rustie matched them all and they cc'ed out to 15cc for now.

I noticed that after about 10 minutes of riding last Thursday - the first
time since April - that everything must have seated in again and the thing is
running very consistently now.  I'm running Turbo Blue 112 octane Racing Fuel
- to keep the knockies away and I'll play around on it like it is until
winter sets in.  After that, I'll work with Rustie on getting the compression
down to where it needs to be.

I'm VERY impressed with my bike now.  I've got 150 kilometers on it since I
got it back together Wednesday night and the power is wonderful.  It pulls
off the line better than stock.  It seems smoother and torquier.  It hits
like a freight train about 6.5K and will rev WAY into the red.  Right now,
it's not jetted quite right on top - 155's with the K&N setup, which, by the
way sounds great, but I'll get it soon.  I'm in love with the midrange power
anyhow.

The engine is very easy to ride, developing power very smoothly, yet quickly.
 3rd gear and a couple of 4th gear wheelies over small rises definitely get
your attention!  First gear is just to get it off the line from a
standstill...it wants to put the front wheel over my head if I hit it very
hard.  I'll ride it like it is for a bit, tuning and tweaking, seeing what it
will do until winter comes along.

My plans for the bike now basically include getting the compression where it
needs to be, getting it tuned correctly and the winter project will be
putting =9193 or =9194 RGV250 bodywork on it.  Craig Wurtele is looking into
getting some out of Japan for me.

I'm running a Randy Norian modified pickup coil
in my bike right now.  It's set at about 2 degrees of advance.


I'll see if I can't get a few pictures for the site!
One last note: I'd really like to thank Rustie, Randy Norian, Bob Truelson,
Mark Russell and Geoff Battick for the help, info, incite and direction on
this project.  From the preliminary results I've seen, I've got a winner!!!

Richard

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