RG500 GAMMA SERVICE TIPS

Service Info
RG Specs
400/500 Differences
RG GP History
Transmissions

Miscellaneous


Gammagir1
RG500.com
Cycle 85

RG500 Specs:
498cc
2 Stroke Sq. Four
406 lbs Wet
4.5/1.3 Gal Tank
279/72 Kms Range
6 Speed Tranny
Rotary Valves
28mm Flat Mikunis
7.0-1 Compression
96 Horsepower
110/90 16 F Tire
120/90 17 R Tire
56.1"  Wheelbase
25.2 Degree Rake
31.3" Seat Height
5.8" Clearance
0-60 in 3.04 sec
1/4 M in 11.37 sec
Braking 60-0 111ft

 

 

 
Suzuki waited 11 years before releasing the square four RG500, a brilliant half-litre sports two stroke, thus capitalizing on an immense amount of development in the premier class of Grand Prix racing. The fact that the
street version of the GAMMA is as potent as the 1976 world championship winning RG is quite astonishing but sadly these 153 kg weapons arrived on our shores just as the government legislated them out of existence.
Stringent emission and noise standards allied to the introduction of unleaded petrol into Australia made 1985 the last year RG500 GAMMAS (and Yamahas RZ500) scored compliance plates. The GSXR-750s kept the GAMMAS at bay on the racetracks which, perhaps, gained them a greater marketing impetus but the RG is an extremely rapid and well balanced machine that a great number of experienced riders missed out on. And if you are lucky enough to own one they are not that difficult to service either.

So lets take a look into what exactly is involved in keeping the 70 kW power plant on the boil! One major pain these days for mechanics is the lack of centrestands on bikes like the RG. A pair of car stands can be purchased and
one under either side of the swing arm supports the machine firmly - thus allowing all service operations such as chain lubrication and adjustment, raising the front end off the ground to check or adjust steering head bearings or to remove the wheel or forks.

I recommend taking the bike for a ride prior to service in order to warm up the gearbox oil and the chain. If the chain is dirty and somewhat neglected, its advisable to wash it with a brush and kero beforehand - don't use harsh
solvents or degreasers that may deteriorate the Orings. Then set the bike up on the stands and make sure the rear wheel spins freely (i.e.. chain not contacting the stands.) Give the warm chain a good lube while either spinning
the wheel by hand or let the motor do it for you at idle in first gear. Now you can get on with the rest of the work.

Firstly there's the usual amount of undressing to attend to and I guess that owners who are keen on 100 percent machine detailing will be familiar with the fairing removal procedures. It is simply a matter of removing the
middle fairing panel for which a screwdriver is required to un clip the zues fasteners at the bottom edge and a 4 mm Allen key for the 3 bolts along the top. Then use a Phillips screwdriver to remove the belly pan.  There are three screws either side - one above the Suzuki logo and two on the steel frame mounted bracket. Next, remove the seat and side covers (3 mm Allen key for cover bolts) and you will confront the bare essentials.  The gearbox has two drain plugs underneath the crankcase. A 4 mm ring spanner or socket is required for the front one and 17 mm for the rear. The suggested change interval (20W40 oil is specified) is every 12,000 km but for the meager 700 ml of oil involved, enthusiasts will no doubt take my advice to half or quarter that interval in the interests of transmission gear longevity.  Fill the gearbox with 700 ml of oil (not friction modified of course) and run the motor briefly.

Wait a minute or so and remove the plug on the face of the clutch cover.  If no oil runs out you should add a little at a time until it begins to do so.  Next items to be dealt with are the fuel system and spark plugs. The replacement
interval on the latter is 6000 km. Fair enough, but gentle usage may necessitate more frequent replacement to maintain crisp performance.  The standard plug is an NGK B 9 ES but if you are not subjecting your machine
to continual hard work then the optional (one range hotter) B8ES would be more suitable.

Spark plug replacement and air filter service can actually be accomplished without actually removing the tank as there is provision to tilt it backwards and prop it in place after the fuel tap has been unbolted. I prefer to have
the extra working space offered by removing the tank although the fuel lines are a bit of a hassle.

The air cleaner is found nestling in an impressive container formed by the steering head casting. The element is made of washable foam that Suzuki recommends be oiled with two stroke oil every 3000 km although this
sounds excessive if the machine is not campaigned in the dirt too often!  I use petrol in a four litre ice cream container to wash the filter (repeat with clean petrol if necessary) then dry it and apply the oil. After working
the oil through the foam squeeze out as much excess as is possible and when reassembling, ensure that the filter seals perfectly against the intake housing.

For once vacuum gauges wont be necessary to synchronize the four throttle slides! But before we go into that there is preliminary work to be attended to, like removing the plastic inlet tracts leading to the carburetors and
draining all four carburetor float bowls to see if any gunk or water is lurking there. Now check that each outer cable has between 0.5 and 1.0 mm of free-play at the point of entry on the carburetor top. Without the specified play, engine speed could increase when turning the handlebars and it would also not be possible to lower the idle speed.
The slides should all be open an equal amount at idle for smooth tick over. Off idle response with the engine at operating temperature should be crisp and the engine should immediately settle down to an even idle after cracking open the throttle. The latter condition is largely controlled by the pilot air screw that enters a passage in the side of the carb bell mouth. The specification is for 1 5/8 turns out but this one responded best to a setting of 1 1/2 turns.
More turns out represents a leaner idle mixture but regardless of the setting, they should all be equal.

You can use a thin piece of wire or a drill bit as a gauge for synchronizing the slides at idle (about 0.5 mm is a starting point but this doesn't mean that the idle speed will automatically be correct) and its simply a matter
of turning each idle stop screw by an equal increment.

Large stop screws designed to be grasped by human fingers (average sized ones at any rate) feature on the two rear carbs but Suzuki apparently doesn't concede that an owner may be able to perform four incremental  adjustments, so the front pair have semi hidden screws (adjacent to the fuel inlet pipes) that require a screwdriver to turn.  In other words they only want you to turn the idle up or down on the rear cylinders which is not conducive to my brand of tuning!

Now look at the slide and you'll notice a dot in the center. The next step is to somehow wedge open the throttle grip (I use a strip of rubber) so that the top of the dot aligns exactly with the top of the carburetor bore.  Simply, if the slide heights are found to differ its a matter of determining the one that is opening the least, lining it up with the bore and lowering the others by giving the cables extra free-play. Snap the throttle open and closed a few times, re-employ the ingenious device you have come up with for locking the twist grip and re- check the adjustment. Hopefully, at the finish, the cable play wont exceed 1.0 mm because too much play will prevent the slides from opening fully. A bad value situation for against the stop types!

Now that the dots are aligned perfectly, leave the throttle in that position (for chrissakes close it before attempting to fire the thing up!) and proceed to check the oil pump al alignment marks. The pump resides above the countershaft sprocket. If the mark (a line) on the control lever doesn't exactly align with the fixed index mark then adjust the pump control cab cable to suit by loosening the lock nut  and adjusting the outer cable length by turning the threaded body.  Don't forget to tighten the lock nut.  That's about it for the fuel and oil systems, but the automatic exhaust control (AEC) cables can be checked while delving in the vicinity. (A few drops of oil for all the cables - clutch, throttle and AEC - is recommended every now and again too.)  The specifications require each of the four cables to have a slight free-play of 0.5 mm but they probably wont need attention.  The control unit is electronically activated so that between 7500 and 7800 rpm the actuator pulley instantly rotates the valves (via the cables) which closes off the exhaust sub chambers thus effectively decreasing the exhaust header volume. From that point on she's on the pipe so to speak by virtue of the fact that the reverse sine pressure waves arrive at the port sooner causing a more efficient induction of fresh mixture. The whole setup is basically maintenance free and you would be made well aware if a problem did occur.

Final servicing tasks may include clutch lever free play (2-3 mm), chain tension (20-25 mm play), tire pressures, general electrical check (bulbs etc.), and charge rate (13 .5 V -15.5V @ 5,000 rpm). The coolant is supposed to be
replaced every two years and don't forget that no grease nipples are provided for the swing arm and suspension linkages (nothing new) so you may feel inclined to spend a wet Saturday arvo dismantling the whole show to
introduce some fresh grease.

Before closing, a word on the 6,000 km recommended interval for de-coking the  exhausts and cylinder heads - you'd have to be keen!  Firstly,  it's completely unnecessary and secondly, there's a considerable amount of work
involved. I can envisage the performance benefiting from an exhaust de-coke at around 20,000 km but modern lubricants wont really cause detrimental carbon deposits on the piston crown and in the combustion chamber. So leave the heads in place until there is a real need to remove them such as new piston rings or a rebore.   Sorry, I cant really estimate how far down the track that will be.

Service Data and Specifications
Cylinder numbering      1-LF, 2-RF, 3-LR, 4-RR
Displacement                498 cm3
Bore and stroke            56 x 50.6 mm
Compression ratio        7.0 : 1
Oil pump discharge       3.2 - 4.0 ml per minute @ 2000 rpm (fully open)
Pilot screw                     1 5/8 turns out
Idle                                 1350 - 1560 rpm
Fuel level                       5.5 mm +/- 0.5 mm
Float height                   17 mm +/- 1mm
Ignition timing (CDI)    14 BTDC below 1700 rpm, 26 degrees 2700 - 6000,11 above 9500
Spark plug / gap            NGKB9ES 0.6 mm - 0.8mm
Charging voltage          13.5 - 15.5 V @ 5000 rpm
Steering geometry        rake 25.5 trail 110 mm
Fork Oil                         15 W
Fork Oil level                97 mm
Fork Oil capacity          441 ml
Fork air                         standard setting zero
Drive chain slack          20 - 25 mm
Oil capacity                   Gearbox 700 - 800 ml, Tank 1.5 litres
Coolant capacity           2 litre, 250ml catch bottle 50 : 50 mix anti freeze water
Fuel type                       85 - 95 octane (or higher) UNLEADED
 

Service Intervals (As per service manual recommendation P/N99500-14000-01E)
3000 km         Air filter
6000 km         Battery, replace plugs
12,000 km      Transmission oil
2 years           replace coolant and brake fluid