Many GasGas Pro owners experience clutch drag. The GasGas Pro clutch is very sensitive to the 'finger height' and the currently available complete clutch pack is too thick resulting in noticeable drag - the slave cylinder 'top hat' can't engage the 'shallower' finger height to hold tension or complete disengage. If a 2.00mm steel plate is replaced with a 1.30mm-1.50mm steel plate, the finger height will be too high resulting in slip - top hat stays engaged. The GasGas Pro uses a diaphragm clutch design that is different from mainstream motorcycle clutches: I recently replaced my Pro clutch pack and discovered the following: GasGas only sells the complete clutch pack MT280232055 : 3 Friction plates MT280232051 and 2 steel plates.MT280232050 . See note below.. Each steel plate in the complete clutch pack is 2.00mm thick. 2002-2003 clutch packs were different MT280432055 . Early 2002 friction plates MT280232051 were prone to swelling; current friction plates do not swell in ATF. The 1.50mm MT280232050 , 1.40mm MT280232050/4 , and 1.30mm MT280232050/3 steel plates are no longer available. If used with the current clutch pack to replace one of the 2.00mm steel plates, the overall thickness will be too thin. If, post 2006 model, both steel plates measure 2.00mm and the friction plates vary in thickness: one friction plate is 2.20mm and the other two are 1.80-1.85mm for a overall thickness of 10.00mm? ( I realize the math doesn't add up from the factory specs) AND The correct specification is: No less than 9.75mm and not more than 10.05mm How do we build a clutch pack that measures 9.75mm +/- 0.1mm to acheive the desired 17mm +/- 1mm 'finger' to inner hub depth? I ended up going through all my old friction discs to build the appropriate clutch pack. I had trouble reverse bleeding the clutch and discovered one of the two orifices in my AJP master cylinder (small reservoir) was blocked. I couldn't clear the blockage; so I replaced the master. I discovered that the master cylinder bore and stroke was relatively the same between the AJP long and short reservoir styles. Replaced the O-rings in the slave cylinder for good measure. The GasGas Technical Bulletin (10/2006) updated 10/2012 http://www.trialspar...ober_2_2012.doc recommended conversion from DOT4 to mineral oil. We since converted back to DOT5 by replacing the slave cylinder O-rings with MT280432047.. We found the Carquest part number CTC407008 for Viton® O-rings for the slave cylinder a bit tighter fit than the OEM MT280432047 Note: ADDENDUM: The current replacement is the complete clutch pack which: The critical requirement for proper clutch operation is the depth of the finger height to inner hub (essentially the angle): 17mm +/-1mm which is usually achieved with thecurrent OEM replacement clutch pack, but probably on the thicker side as the new clutch packs measure according to the factory: The ideal clutch pack thickness is 9.75 +/-0.1mm which currently can only be acheived by using thinner (i.e. used) discs. For those that run the smaller slave cylinder volume (Magnesium cases: 2002, Raga, S3, etc). the tophat travels slightly further with the same AJP master cylinder, and this makes the issue more prominent. 16.8mm-17.0 mm finger height to inner hub measurement seems ideal. A shallower finger to inner hub height due to a thicker pack increases drag; which seems acceptable to most riders, the opposite slip occurs with too thin a clutch pack (worn out discs). Using any of the previous 1.30mm-1.50mm steel plates (or the mentioned Jitsie 1.6mm) with the current fiber plates will likely result in too thin a clutch pack.