Information bulletin

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Information bulletin

     th* GASGAS Pro Technical bulletin April 12 2007

Application: 2002~2007 GASGAS “Pro” model motorcycles.

    Subject: Clutch slave cylinder repair hints, applicable o-rings, and alternative parts availability. Information on water pump updates. Periodic maintenance and repair.


For 2002 GASGAS pro. The “clutch cover” update kit:

    Beginning in the 2005 model year, all Pro model hydraulic clutch systems use mineral oil. (Applicable to the 2004 Adam Raga special edition models also)

     A “kit” is available to convert the clutch cover~slave unit on 2002 Pro motorcycles, into the improved 2003-06 aluminum redesigned version. This kit includes all components necessary to convert from DOT4 brake fluid to Mineral oil.



    The kit includes the following: One 2003~06 type aluminum clutch cover (2002 models are magnesium) all necessary o-rings gaskets, and seals. A seal kit to convert the master cylinder on the handlebar to accept the mineral oil. Contact the GASGAS dealer nearest you for more information. GASGAS part number MT280532001CR

NOTE: Also available is the RACING CLUTCH COVER. This design is the 2003~04

    type in MAGNESIUM, with gold anodized finish. Fits all Pro models.

    GASGAS part number MT280332001RA

    NOTE: The 2005-06 Raga cover is part number MT280532001RA

    Note: For 2002 conversion, 2003-type slave piston, and spring are necessary.

    Clutch cover o-ring selection and applications:

Application: 2002 model Pro (all engine sizes)

    With original magnesium 2002 clutch cover using two o-rings.

    Fix for early 2002 Pro machines with problems of o-ring expansion (swelling) We have found a green o-ring that are actually the USA "SAE" size, but are a nice fit on most 2002 bikes with good results. These do not swell when exposed to brake fluid and transmission oil. Get them from Rising Sun Imports, or you can order them at your local Car Quest store.

    Green o ring, carquest part number CTC407008

    Exception: Please note that on some bikes where the "post~piston" tolerance is tighter, the green o-rings may not fit correctly. You will know this, as the slave piston will be very difficult to install, or may not pass over the green o-rings without being forced. In this case, use the black 2003~06 o-rings as described in the next paragraph. 2003~06 black o ring, GASGAS part number MT280432047

Application: 2003~04 model Pro. With brake fluid system. All engine sizes.

    (Except the special 2004 Adam Raga edition)

     The 2003-04 standard production machines use one o-ring and one cup seal in the clutch slave.

     Rising Sun Imports now has a high quality black o-ring from GASGAS in the correct

    metric size. Used in the innermost position on the 2003~06 version, and fits the 2002 as well. (At both post positions.) They are made of a special Teflon coated aerospace synthetic rubber. This rubber is impervious to most common petrochemical compounds. Please note: As previously mentioned, the 2002 motorcycles with tight slave piston tolerance are best with this 2003~06 type o-ring.

    2003~06 black o ring, GASGAS part number MT280432047

    2003-04 cup seal for brake fluid. Part number MT280332049

Application: Special 2004 Adam Raga edition, most 2005 Pro models

    These machines use mineral oil in the hydraulic clutch system.



    The clutch cover uses an o-ring and a cup seal on the outer post position. These rubber compounds are designed for mineral oil.

    2003~06 black o ring, GASGAS part number MT280432047

    2004 Raga model, 2005 mineral oil cup seal MT280532049

    Hydraulic clutch mineral oil part number MT280432700

    Clutch cover o-ring selection and applications. Continued

    Application: Special 2005 Adam Raga edition, some late production 2005 Pro models, and all 2006 Pro models

    These machines use mineral oil in the hydraulic clutch system.



    Effective mid-year 2005, the clutch cover uses two o-rings on both post positions. These rubber compounds are designed for mineral oil. If your 2005 machine uses an o-ring, and a cup seal, refer to above specifications for 2004.

    Both o-rings are the same. The part number is MT280432047

    Hydraulic clutch mineral oil part number MT280432700

    Helpful hints:

    NOTE: Always work clean, with no oil contaminants on the parts. (Use "carb cleaner" on the metal parts, blow dry to absolute clean. Drain or disconnect the hydraulic hose from the cover so fluid doesn’t enter while you work.)

    Use "sparingly" only silicone grease to lubricate parts for assembly.

    (Find the grease at NAPA or Car Quest etc..)

    Clean hands; do not contaminate the o-rings with fluids or cleaners. Do this, and the repair will last for a long time.

    Why so clean? Flooding the slave with fluid on piston assembly, can cross contaminate the two systems (Trans oil~brake fluid). Oil on your hands can contaminate the o-rings during assembly.

    Fluid types for hydraulic system:

    NOTE: We are now using DOT 5 silicone brake fluid in pre-mineral oil systems and

    have had excellent results. Alternatively, use the factory recommended DOT 4. On mineral oil systems, you may obtain genuine GASGAS mineral Oil from your GASGAS dealer.

    Hydraulic clutch mineral oil part number MT280432700

    Transmission oil:

    Recommend type: ATF DEXRON II

    Alternatives: NOTE: We have a few customers using the type "F" automatic transmission oil with good results. Dramatically reducing, and in one known case eliminating the clutch pack swelling.

    NOTE: GASGAS Spain recommends only Dexron III automatic transmission oil at this time.

    Oil type warning:

    Never use synthetic oil in the transmission~clutch. The synthetic oils are

    “stickier” and this adhesion tendency, when applied to the areas between the

    clutch plates contribute to excessive clutch drag. Some brands of synthetic oil will chemically react when mixed with water, (from creeks, rain, or waterpump seal leakage). This reaction alters the pH factor of the oil. This acidic condition accelerates corrosion of steel engine parts, and loosens the bond of the clutch fiber plate material. Please do not second-guess this information. We have twelve years of experience with the Herbringer/Adige brand clutch plate materials, and we are in direct contact with the technical departments at Herbringer, Adige, and GASGAS Spain.

    New clutch bolts and tool:

Beginning in the 2003 model year, there is a new bolt for the clutch. End forever

    the aggravation of the ten little Allen clutch bolts on the pro. This new bolt has been designed exclusively for GASGAS and uses a 7mm 12-point socket, or box end wrench. No more Allen bolts to “round out”.

The bolt part number is MT280332077 (replaces T0324010)

    The metric 12-point socket tool part number is MT280332077UTL

    Clutch pack measurement:

     In the diagram below, you will find the correct measurements for proper functioning of the clutch featured on the “pro” model TXT. If you see that the measurement of the complete disc pack is higher than specified, you should correct this by making adjustments using a steel shim disc. These discs are of varying thickness. (Similar to those used on the edition model.) We have shim discs available in the following thickness: 1.6 mm, 1.5mm, 1.4 mm and 1.3 mm.

    1.3mm Part number MT28023205/3

    1.4mm Part number MT28023205/4

    1.5mm Part number MT28023205

    1.6mm Part number MT28023205/6

    Complete clutch pack. Fiber and metal discs. MT280432055

    2006 model Installation note: The clutch fiber discs have variations in thickness. This is done at the point of manufacture to ensure precise total pack width.

    IMPORTANT: Of the three fiber clutch plates, one is noticeably thicker. This thickest plate MUST be the one that is placed into the engine first. (Farthest into the interior and against the rear surface of the center clutch driven hub.)

    NOTE: If the ten clutch fulcrum levers (fingers) have no free play, this is an immediate indication that the thickest fiber plate is not is the innermost position.

    Proper assembly sequence of clutch slave components

    How to properly reassemble the outer clutch cover

    WARNING: The motorcycle must be laid on its side when replacing the clutch cover. As the following photos show, if the clutch outer cover is assembled while the motorcycle is in an upright position the clutch actuation fingers can fall outward by the force of gravity. During reassembly, the slave piston can get behind one or more of the fingers. There is no way to determine that the installation is correct unless the motorcycle is laid upon its side for this operation. This way, the force of gravity insures that the clutch actuation fingers are in the proper position. If this procedure is not followed, upon starting of the engine, the internal parts of this assembly can be seriously damaged.

    The potential problem associated with improper assembly is shown in

    the following two photographs.

    PHOTOS OF IMPROPER assembly of clutch slave and

    fulcrum lever components

    For the reason shown in these cutaway photo examples, we recommend the machine always be placed on its side for the replacement of the clutch cover. This way, gravity insures that the clutch fulcrum levers (fingers) stay in position during


    Kick Start Shaft alignment (INDEXING):

    When assembling the kickstart shaft, the indexing of the gear, shaft, and spring are as shown in the two photos below. When the gear is correctly installed on the shaft, the spring will align as shown in the photo on the left. The right photo shows the position of the parts when checking for proper indexing.

    NOTE: There has been a redesign of the shaft and gear. The shaft and gear are now sold only as a matched pair. The part number is MT280226002R

    Water Pump information, Pro 2002~07:

Beginning in 2004, there are three changes to the waterpump.

    1 The center shaft has a new heat treatment. The part number remains the same. 2 The impeller is made of a new material. The part number remains the same.

    3 The outer bushing (drain cap) is made of a new alloy. It has a much longer life than the original model. The new cap uses a “Torx” bit for removal, and installation. The

    original one used an Allen wrench. (See photo) The part number remains the same.

    TRIAL PRO MOTORCYCLES- Periodic revisions:

    One of the most important things when using the clutch is the quality of the oil in the engine. The oil on a trial engine, apart from the lubrication of the gears, has the Responsibility of dissipating the clutch heat. Due to the importance of the clutch in trial, it is normal that the oil deteriorates very quickly. In order to have correct operation, Gas Gas recommends a periodic exchange of the engine oil. The humidity that can be produced by water coming in the engine or by internal condensation can adversely affect the operation of the clutch. (Remember that the clutch discs are made from Kevlar and other organic materials that are very sensitive when they are exposed to water or humidity). The oil that GASGAS recommends is ATF (Automatic gearbox Dexron III) It is important to be certain that the radiator breather hose is not depressed. If this tube does not have free aspiration, the cap release valve will not work properly and it is possible that accumulated pressure of more than 1 bar (14.5 PSI) can affect the refrigeration circuit. If this happens, the pressure in the circuit will increase and it may cause leakage of the water pump seal.

    Also: When assembling the fuel tank, be certain to check the correct position of the protection rubber flap placed in the filter box. If the position is not correct, it could clog the air intake, resulting in a loss of engine performance (power).

; As always, specifications are subject to change without notice.

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