Here are all of the chassis related differences between the 1987, 1988, 1989, and 1990 LT500Rs, and a brief description of how they changed. All chassis assemblies not listed have identical parts from the 1987 models to the 1990 models.


AIR CLEANER
The 1988 and later models have a different AIR CLEANER ASSEMBLY. The differences are the airbox has a tab to mount the FILTER HOLDER instead of a threaded hole, and it comes with the following different parts. The FILTER HOLDER is different because it mounts differently. The SNAP PIN is different than a WING BOLT. The WASHER is different.
BRAKE LEVER
The 102037 VIN and earlier models have a different THROTTLE CASE ASSEMBLY. The differences are it uses an 8mm by 5.6mm long LEVER shaft, an 8.4mm by 15.5mm by 1.6mm WASHER, an 8mm by 14mm by 4mm DUST SEAL, and doesn't use an internal WASHER behind them.
The 102038 VIN and later models use the normal THROTTLE CASE ASSEMBLY. The differences are it uses a 8mm by 4.5mm long LEVER shaft, an 8.2mm by 14mm by 1mm WASHER, an 8mm by 12mm by 3mm DUST SEAL, and does use an 8.2mm by 12mm by 0.5mm internal WASHER behind them.
The 1989 and 1990 models have a different THROTTLE CABLE PIN. The difference is it is 7mm long, and the earlier models use a 6mm long pin.
FOOTREST
The 1988 models have a different FRONT RH FOOTREST BAR, FRONT LH FOOTREST BAR, and FRONT GRIP. It also uses 4 10mm by 43mm bolts to secure the FOOTREST BARS.
The 1989 and 1990 models have a different FRONT GRIP. The difference is it uses a thick bar, and the the earlier models used a PAD and CLAMPS. They also use FRONT GRIP CAPS, and the earlier models do not. They also have a different REAR GRIP, in addition to the different FRONT RH FOOTREST BAR, FRONT LH FOOTREST BAR.
FRAME
The 1988 and later models have a different FRAME. The differences I know of are the steering shaft lower area, the footrest mounting areas, and the a-arm mounting locations. They also have a different UPPER CHAIN CONTROL ROLLER. They also have a different UPPER SPACER. They also have 2 different LOWER WASHERS instead of 1 upper and 1 lower.
FRONT CALIPERS
The 1989 and 1990 models have different RH and LH CALIPER ASSEMBLIES. The difference is that the later calipers are unpainted, and the earlier calipers are painted black.
FRONT FENDER
The 1988 models have a different TAPE SET and EMBLEMS. The TAPE SET says "QuadRacer" in 765 Dark Blue script, with a slight 25Y Marble Science Yellow shadow, a background of 2 blues, the upper one is 08L Light Blue, and the lower one is 08K Vivid Blue, all with an outline of 25Y Marble Science Yellow. The EMBLEMS say "SUZUKI" in 765 Dark Blue script, with a background of 25Y Marble Science Yellow.
The 1989 models have a different RH TAPE SET, LH TAPE SET, and CENTER FENDER EMBLEMS. The RH and LH TAPE SET say "SUZUKI" in 08K Vivid Blue, with a background of 2 stripes, the upper one is 08L Light Blue, and the lower one is 08K Vivid Blue, with a center of 064 Pure White, all with an outline of 25Y Marble Science Yellow. The CENTER FENDER EMBLEMS say "QuadRacer" in 064 Pure White script, with an outline of 26E Champion Blue Number 2. They also have different FRONT FENDER BOLT WASHERS, REAR CENTER FENDER SCREWS, REAR CENTER FENDER SCREW WASHERS, FENDER BRACE SCREW WASHERS, WARNING LABEL, WARNING LABEL NUMBER 1, and WARNING LABEL.
The 1990 models have a different RH TAPE SET and LH TAPE SET. They say "SUZUKI" near the front in 064 Pure White, and "QuadRacer" near the rear in 25Y Marble Science Yellow script, with a background of 3 blues, the upper one is 08L Light Blue, the middle one is 08K Vivid Blue, and the lower one is 33N Marble Parsec Blue, all with an outline of 25Y Marble Science Yellow. They also have the different FRONT FENDER BOLT WASHERS, REAR CENTER FENDER SCREWS, REAR CENTER FENDER SCREW WASHERS, FENDER BRACE SCREW WASHERS, WARNING LABEL, WARNING LABEL NUMBER 1, and WARNING LABEL.
FRONT MASTER CYLINDER
The 1990 models have a different FRONT MASTER CYLINDER ASSEMBLY and CAP. The difference is that the later assembly includes a different CAP that I assume says to use only DOT 4 fluid, and the earlier models could use DOT 3 or 4.
FRONT WHEEL
The 1988 models have 2 sets of different FRONT TIRES. One set are Bridgestones, and the other set are Dunlops. They are different from the 2 sets on the 1987 models.
The 1989 models have 1 set of different FRONT TIRES.
The 1990 models have 1 set of different FRONT TIRES.
FUEL TANK
The 1988 models have a different FUEL TANK, HOSE, and FUEL **** HOSE, and don't use rear CUSHIONS. The HOSE difference is that the 1988 HOSE comes in a 950mm length, and the 1987 HOSE comes in an 890mm length. Both are cut to a finished length of 370mm.
The 1989 models have a different HOSE and FUEL **** ASSEMBLY, also use the different FUEL TANK and FUEL **** HOSE, and also don't use rear CUSHIONS. The HOSE difference is that the 1989 HOSE comes in a 600mm length, and the 1988 HOSE comes in a 950mm length. Both are again cut to a finished length of 370mm.
The 1990 models have different SCREWS, don't use rear CUSHIONS, and don't use LOCK WASHERS. The SCREW difference is that the later SCREWS have a built in LOCK WASHER, and the earlier SCREWS did not.  It also uses the different FUEL TANK, 1989 HOSE, FUEL **** ASSEMBLY, and FUEL **** HOSE.
HEADLAMP
The 1989 and 1990 models have a different HEADLAMP ASSEMBLY and RIM. The difference is that the later assembly includes a black RIM, and the earlier RIM is chrome.
MUFFLER
The 1988 models have different NUTS, 2ND MUFFLER, added CLEAN OUT TUBE, added BOLTS, and MUFFLER CONNECTOR. The 2ND MUFFLER difference is that the later muffler has a CLEAN OUT TUBE and BOLTS, and the earlier muffler does not.
The 1989 and 1990 models have a different 2ND MUFFLER, DRAIN PLUG, MUFFLER BOLTS, MUFFLER LOCK WASHERS, and MUFFLER WASHERS. The 2ND  MUFFLER differences are that the later muffler is black, and has only 1 different DRAIN PLUG and GASKET. The MUFFLER WASHER difference is the later washers are 8.5mm by 29mm by 1.6mm, and the earlier washers are 8.5mm by 28mm by 1.6mm. It also uses the different NUTS, CLEAN OUT TUBE, BOLTS, and MUFFLER CONNECTOR.
REAR FENDER
The 1988 models have a different FENDER TAPE SET, RH 500 EMBLEM, LH 500 EMBLEM, and QUAD RACER EMBLEM. The FENDER TAPE SET is DARK BLUE. The RH and LH 500 EMBLEMS are "500"s in 2 blues, the upper is 08L Light Blue, and the lower is 08K Vivid Blue, with an outline of 25Y Marble Science Yellow. The QUAD RACER EMBLEM says "QuadRacer" in 765 Dark Blue script, and has a background on 25Y Marble Science Yellow.
The 1989 models have a different RH FENDER TAPE, LH FENDER TAPE, 500 EMBLEMS, and REINFORCEMENT BOLT WASHERS. The RH and LH FENDER TAPES are 019 Black numberplate outlines, with thin 25Y Marble Science Yellow inner and outer perimeters. The 500 EMBLEMS say "500" in 2 blues, the upper is 08L Light Blue, the lower is 08K Vivid Blue, with a thin 064 Pure White divider and shadow, and has a background of 25Y Marble Science Yellow.
The 1990 models have different RH FENDER TAPE SET, LH FENDER TAPE SET, RH 500 EMBLEM, LH 500 EMBLEM, FENDER BOLTS, FRONT LH BOLT, REINFORCEMENT BOLTS, REINFORCEMENT BOLT WASHERS, TIRE AIR PRESSURE LABEL, and WARNING LABEL. The RH and LH FENDER TAPE SET are 33N MARBLE PARSEC BLUE numberplate outlines. The RH and LH 500 EMBLEMS say "500" in 3 blues, the upper one is 08L Light Blue, the middle one is 08K Vivid Blue, and the lower one is 33N Marble Parsec Blue, and has a background of 25Y Marble Science Yellow. The FENDER BOLTS and FRONT LH BOLT are different. The difference is the later bolts have LOCK WASHERS and WASHERS built in. The REINFORCEMENT BOLTS are different. The difference is the later bolts have LOCK WASHERS built in.
REAR MASTER CYLINDER
The 1988 models have a different REAR MASTER CYLINDER ASSEMBLY. The differences are that the later assembly includes a different PUSH ROD.
The 1989 and 1990 models have a different REAR MASTER CYLINDER ASSEMBLY. The difference is that the later assembly is unpainted, and the earlier assembly is painted black. It also includes the different PUSH ROD.
REAR SWINGING ARM
The 1988 models have a different SWINGARM, BUFFER, BOLT, LOCK WASHER, WASHER, GUARD STAY, and SPROCKET GUARD BUFFERS. The SWINGARM difference is that the later models use 1 short BOLT, with LOCK WASHER and WASHER to secure the BUFFER, and the earlier models use 1 long BOLT and NUT. The BUFFER difference is the later models have a mounting area on the side, and the earlier models do not.
The 1989 and 1990 models have different EMBLEMS. The difference is the later EMBLEMS have 064 Pure White "Full Floater" letters, and the earlier models have clear letters.
REAR WHEEL
The 1988 models have a different REAR SPROCKET, 2 additional optional REAR SPROCKETS, and 2 sets of different REAR TIRES. The REAR SPROCKET has 2 fewer teeth. One set of REAR TIRES are Bridgestones, and the other set are Dunlops. They are different from the 2 sets on the 1987 models.
The 1989 models use the same REAR Bridgestone TIRES as the 1988 models, and also the different REAR SPROCKET and 2 additional optional REAR SPROCKETS.
The 1990 models have a different set of REAR Bridgestone TIRES as the 1989 models, and also the different REAR SPROCKET and 2 additional optional REAR SPROCKETS.
SEAT
The 1988 models have a different SEAT ASSEMBLY. The difference is that the cover has "NO PASSENGER" heat stamped on the back of it.
The 1989 models have a different SEAT ASSEMBLY. The difference is that the cover has "NO PASSENGER" heat stamped on the back of it, and "QuadRacer" in white script on the back of it. The BOSS CUSHIONS are also different from the 1987-1988 models.
The 1990s model have a different SEAT ASSEMBLY. The difference is that the cover has "NO PASSENGER" heat stamped on the back of it, and "SUZUKI" in white on the back of it. The BOSS CUSHIONS are also different from the 1987-1988 models.
SHOCK ABSORBER
The 1988 and later models have a different REAR SHOCK ABSORBER ASSEMBLY. The difference is that the later shock uses a flathead adjuster to adjust the rebound, and the earlier shock uses an ADJUST PLATE with SCREW.
STEERING SHAFT
The 1988 models have a different STEERING SHAFT. The difference is that the later models use STEERING SHAFT CUSHIONS and the earlier models do not, and the later models do not use the LOWER STEERING GREASE NIPPLE and GREASE NIPPLE CAP that the earlier models use.
The 1989 and 1990 models have a different LOWER STEERING SHAFT BUSHING and BOLTS. The BOLT difference is the later bolts have LOCK WASHERS built in, and the earlier models do not. They also use the different STEERING SHAFT and do not use LOCK WASHERS.
SUSPENSION ARM
This assembly is just too difficult to explain like the other assemblies, so I'll break this one down differently.
The 1988 models have different FRONT SHOCK ABSORBERS, UPPER RH SUSPENSION ARM, UPPER LH SUSPENSION ARM, and different and/or different amounts of SUSPENSION ARM PIVOT BEARINGS, SUSPENSION ARM PIVOT SPACERS, SUSPENSION ARM DUST SEALS, INNER PIVOT DUST SEALS, SUSPENSION ARM PIVOT BOLTS, SUSPENSION ARM PIVOT WASHERS, and NUTS. The FRONT SHOCK ABSORBER difference is the amount of coils in the springs, and possibly also internal valving/oil changes. The UPPER RH and LH SUSPENSION arm differences are the mounting method, and that the later models are round tube and the earlier models are rectangular tube.
The 1989 models have a different LOWER RH SUSPENSION ARM, UPPER RH SUSPENSION ARM, LOWER LH SUSPENSION ARM, and UPPER LH SUSPENSION ARM. The difference is that the later arms are 064 Pure White, and the earlier arms are 126 Pearl Metallic. They also use the different and/or different amounts of SUSPENSION ARM PIVOT BEARINGS, SUSPENSION ARM PIVOT SPACERS, SUSPENSION ARM DUST SEALS, INNER PIVOT DUST SEALS, SUSPENSION ARM PIVOT BOLTS, SUSPENSION ARM PIVOT WASHERS, and NUTS as the 1988 models.
TAIL LAMP
The 1990 models have a different TAIL LAMP ASSEMBLY, LENS, and BULB.
TIE ROD
The 1988 and later models have a different RH STEERING KNUCKLE, LH STEERING KNUCKLE, KNUCKLE STEERING UPPER ENDS, KNUCKLE STEERING LOWER ENDS, RH TIE RODS, LH TIE RODS, RH KNUCKLE STEERING ARM, LH KNUCKLE STEERING ARM, and KNUCKLE STEERING BOLTS. The RH and LH KNUCKLE STEERING ARM difference is the later models are angled, and the earlier models are not.

Another great write up. Nice work Kyle! This needs to be a sticky.

Kyle what is a boss cushion, in the seat section above?

Thanks Kyle great work, I made this a sticky 

WOW that must have taken some research! Thanks!

This is really helpful, thanks for taking the time to write this up!