Pro Clutch Friction Plate Challenges: Current Oem Clutch Packs Are Too Thick

[seavoyage]

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.

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 measure 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 Pro 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:

2006 and newer model Installation note: The clutch fiber and steel discs were changed in the 2006 model year. The three fiber discs have a variation in thickness and the two steel discs are thicker than the previous models. There may be slight variations in thickness of the fiber discs, this is done at the point of manufacture to ensure precise total pack width. The total pack width is 10.0~10.01mm – The two steel discs measure 2.0mm each – Two of the fiber discs measure approximately 1.80~1.85mm thick and the third one is 2.2mm thick. All steel and fiber discs are symmetrical (there is no specific front or back side)

IMPORTANT: Of the three fiber clutch plates, one is noticeably thicker. (about 2.2mm thick) 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.)

Edited July 19, 2013 by seavoyage

[arnoux]

Jitsie sell 1.6mm plates if you need them to achieve the stack height you desire.

Alternative fibres are available from Sureflex, Adige and S3 (complete RACING kits - Hoerbiger friction discs)

The thicker disc does go in first (engine side)

[copemech]

Having read some of this info in the past, I just do not get it! What, Gasgas cannot provide for what they built?

What are they putting in the new ones and what has changed to make it work?

[seavoyage]

Having read some of this info in the past, I just do not get it! What, Gasgas cannot provide for what they built?

What are they putting in the new ones and what has changed to make it work?

The current replacement is the complete clutch pack which:

There may be slight variations in thickness of the fiber discs, this is done at the point of manufacture to ensure precise total pack width.

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

The total pack width is 10.0~10.01mm

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.

Edited July 18, 2013 by seavoyage

[duggan]

Hi

Had the same issue recently with fitting a genuine gas gas clutch, new clutch arrived and measured 10.03mm. I search everywhere to fine a steel plate to reduce the pack to around 9.75 / 9.85 but no joy.

in the end I just fitted the new clutch which made the fingers sit low, at around 15.5 / 16mm. This made the lever heavy and the clutch had a very noticeable drag.

The solution to the problem was to warm the bike up, stick it in third gear, front wheel against a wall while sitting on the bike and give it some grief!!!

Worked a treat! clutch was lighter and the drag and bite point improved, its about perfect now.

I am unsure about if this would work with an aftermarket brand clutch, but it seems the genuine gas gas clutches bed down significantly which explains to me why they seem slightly over sized when new.

Have since re measured the clutch fingers and they now measure correct at 17mm.

Edited July 25, 2013 by duggan

[lineaway]

Thanks duggan! I forgot our importer told me to burn in a new clutch in forth gear. That was years ago, but still needs to be done today!

[copemech]

Thanks duggan! I forgot our importer told me to burn in a new clutch in forth gear. That was years ago, but still needs to be done today!

I guess that may work! Seavoyage, Burn it!

[sawtooth]

Can you explain the finger measurement? Am trying to set my clutch/lever up currently. I also have a bit of drag so will try burning it a little as described above.

[jse]

Can you explain the finger measurement? Am trying to set my clutch/lever up currently. I also have a bit of drag so will try burning it a little as described above.

The finger measurement refers to the distance from the inner clutch hub to the top edge of the "fingers" (how far the "fingers" are angled in or out from the inner clutch hub surface). A caliper is the easiest way to get an accurate measurement. The finger angle generally affects three things: how much pressure is exerted by the clutch spring, the mechanical advantage the fingers exert in relation to the pressure plate and the range of travel in clutch engagement.

Jon