Suzuki RG500 GAMMA


SUZUKI RG500 GAMMA - SUZUKI RG500 GAMMA - SUZUKI RG500 GAMMA

Gearbox Failures and Updates


Many thanks to Richard, Bob and all the others that contributed

Part codes

Here's a little (very little) bit of "inside info"...the first three digits of the second half of the part number designate the model (if any) that the part was designed for. 21A is the RG500 and 20A is the RG400. If a part developed for the RG400 was deemed acceptable for use on the 500 it was not changed (for example the shiftforks above), but if a new part was deemed necessary it was given the 21A designator and (frequently) used on the 400 as well. The digits after the first three in the second half of the part number) indicate revisions (usually), for example 21A00 may be revised to a 21A01 if a minor change, a more significant change may result in 21A00 becoming 21A10. So, the 6th driven gear (24361-21A11) must have had a fairly significant change and then a further minor change.

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Common noises associated with the RG500's transmission:

Noise: Clunk when engaging into first gear from neutral
Cause: At a standstill, with the engine running and the bike in neutral, the transmission is spinning. When you engage 1st, the spinning transmission is suddenly brought to a standstill. What you are hearing are the drive dogs on 5th driven going into 1st driven and the tranny slamming to a stop..

Noise: "Gamma Rattle" - Rattling clutch when in neutral, changes when clutch lever is pulled in.
Cause: Some noise is normal. This can be a couple of things. The thrust washers that are on each side of the needle bearing that the clutch basket rides on can become worn, letting the entire clutch basket/primary driven gear move laterally on the countershaft. The needle bearing that the clutch/primary driven gear ride on may be worn. The inner clutch basket may be worn where it rides on the splines ofthe countershaft. The nut holding the inner basket can then begin to back off allowingmore movement and wear. What makes the sound become less when the clutch lever is pulled is that pressure is applied from the outer clutch plate is to the entire clutch basket, thus "pulling" out any "loose" movement. Hence the rattle goes away .=

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Post-tragedy tips

Scott Baldwin writes: The gear fractured, and a chunk about 1/8 of the whole gear crunched its way through the cases. There is another hole above the countershaft, so more pieces may have come flying off, but I don't know for sure, yet. It made some really badcrunching, grinding, banging, noises when it let go, so I'm expecting to find more broken parts, though. =0D One important thing about tranny failures that you must not overlook is that pieces from the broken gears sometimes find their way into the forward part of the enginedestroying crank gears and bearings as well, possibly the water pump gear too. Clean crankcases thoroughly and inspect EVERYTHING. Nothing quite like throwing everything back together and hearing another unsuspecting rattle coming from a thrown crank bearing. = ------------------------------------------------------------------------------------------------------------------

OLD vs UPDATED parts

The Suzuki parts book calls the countershaft a DRIVESHAFT. This is the shaft with the chain sprocket on it, and the parts book calls clutch driven shaft the COUNTERSHAFT. The drive gears are located on the countershaft and the driven gears are on the driveshaft. Confusing enough?

From 1990 Service Manual: Factory installed Gearbox Updates: 3/4th Drive Gear & 5th Drive gear - effective on and after engine # 102121
2nd Driven Gear & 6th Driven Gear - effective on and after engine # 106338

2nd Driven Gear



6th Driven Gear


All the Driven Gears, with the exception of 1st have been updated along with 3 locking washers. -------------------------------------------------------------------------= -----------------------------------------

Part Numbers

Here is the complete parts listing of the Transmission - Figure 14 in the Parts Book. All part numbers are the latest upgraded part. They are listed the same way the parts book lists them. A "*" after the part description indicates the part number that may not be in the parts book, depending on the age of the book.
Ref #     Part #              Description                   Qty
  1  24121-20A01         Counter Shaft (NT:11)         1
  2  24221-20A01         Gear, 2nd drive (NT:16)       1
  3  24231-21A00    Gear, 3/4th drive (NT:21/23)* 1
  4  24251-21A00    Gear, 5th drive (NT:22)*      1 =

  5  09301-22002         Bush                     1
  6  24261-20A02         Gear, 6th drive (NT:23)       1
  7  09301-22003         Bush                     1
  8  09380-22009         Circlip                       1
  9  08331-11229         Circlip                       2
10   24741-20A00         Retainer                 2
11   02122-06167         Screw                         2
12   09267-25002         Countershaft Bearing, RH      1
13   08110-62030         Countershaft Bearing, LH      1
14   24131-20A00         Driveshaft                    1
15   24310-20A02         Gear, 1st driven (NT:29)      1
16   24320-21A10         Gear, 2nd driven (NT:28)*          1
17   24331-21A10         Gear, 3rd driven (NT:29)*          1
***  24332-21A10         Bushing for Gear, 3rd driven* 1
18   24341-21A10         Gear, 4th driven (NT:27)*          1
***  24342-21A10         Bushing for Gear, 4th driven* 1
19   24351-21A10         Gear, 5th driven (NT:23)*          1
20   24361-21A11         Gear, 6th driven (NT:22)*          1
21   08211-20321         Thrust Washer            1
22   09167-25013         Lock Washer                   1
23   09169-25001         Washer                   1
24   09380-25003         Circlip                       3
25   09167-25023         Lock Washer*             3
26   09262-20078         Driveshaft Bearing, RH        1
27   09262-25073         Driveshaft Bearing, LH        1
28   09283-32003         Oil Seal (32x42x6)            1
29   27510-20A0          Sprocket, Engine (NT:16)      1
30   09159-20001         Nut                      1
31   09167-25019         Lock Washer                   1
32   09180-25076         Spacer (25x32x16.4)           1
33   09280-25001         O-ring (D:1, ID:24.5)              1
=0D
Items that may require replacing when servicing the transmission:
Parts Book - Figure 16
Ref #     Part #              Description                   Qty
 1   25211-20A02         Fork, No. 1                   1
 2   25221-20A02         Fork, No. 2                   1
 3   25231-20A02         Fork, No. 3                   1
 4   25411-20A02         Shaft, Fork No.1*             1

Other parts needed for Transmission Servicing:
Parts Book - Figure 3
18   11332-20A00         Retainer, T/M cover No. 1          4
19   11332-20A10         Retainer, T/M cover No. 2          3

Parts Book - Figure 4
 2   11482-20A01         Gasket, Clutch Cover               1=
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Factory assembly error

>It turns ot there was a tranny ring clip installed backwards, at
>the factory.  Those things are made by stamping them out of
>Roserunner

Yes, that is a point worth noting.  The Japanese are not immortal when it 
comes to motors.  I [Bob T]'ve done a couple of tranny updates and noticed 
a few glitches myself.
One of the new reinforced sixth gears I bought wouldn't 'nest' properly 
inside the adjacent gear.  Its teeth hung up on the inside of the wider gear 
(2nd) before the dogs engaged the slots smoothly.  Suzuki Canada said that it 
was a millimeter wider than the other gears in it's stock and sent me a
replacement.  
On a less important note, if you measure the spacers and clips that you get, 
they will range in widths quite noticeably using a dial vernier gauge. 
For one gear, I couldn't even get the new supplied spacer to fit between it 
and a circlip.  I had to measue a bunch of older and newer clips and spacers 
and find a combination that just fit.  I recommend that you take this 
approach as you got through each gear/spacer/clip sequence to balance out the 
tolerances, when you do a rebuild or update.  
For those who don't know, there were seven gears that were updated through 
the years of gamma production, and then some post production.  2nd and 6th 
are the most important to pay attention to. 

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Update description

If you've got an early bike (built in '85 or so, you probably don't have any updated gears - but you'll be able to tell when you take it apart) Updated 2nd and 6th driven gears have deep (visible) undercuts and must be installed as a set (the dogs on 6th have also been reinforced at the base). New 3rd and 4th driven gears have been hollowed out and new hardened inserts (bushings) now ride between them and the shaft - they also must be installed together because of new undercuts. A new 5th drive gear is deeply undercut and must be installed with the new undercut 3rd/4th drive gear set. Rob K kept track of what engines numbers have what, and I think it goes like this: Engines after 102120 (mine was pre) got the upgraded 3/4 drive and 5th drive gears. Engines after 106338 got the 2nd and 6th driven, and after an unknown later date (post-production I think), 3rd and 4th driven gears have a different construction completely. There is a new inner ring that is anchored in the shaft grooves and the surrounding 'gear' rotates with respect to the inner part. This was done to alleviate the amount of wear that was showing up here. And of course, if any of your other gears (non-updated) have worn-looking dog or slot areas, best to replace them too). That's it. Lottsa gears (seven I think) and lottsa money. You can do it yourself if you take very careful note of dissassembly and just duplicate in reverse order. The cassette-style tranny is wonderful - take off one cover and there it is. Of course, use the large service manual for the bike and familiarize yourself with the drive and driven gear set-ups. It is do-able, if you are not mechanically challenged, and you'll need some extras like a clutch remover (need an old plate), a 27mm socket, and a good vernier caliper to check spacer thicknesses.

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Rob Koopman ( Rob.Koopman@inter.NL.net ) RG500 index RG500 Index