03 Pro Clutch...again

[dabomb]

Hi chaps,i need to sort this dragging clutch out on my sons bike.its not a major problem but i just want it right for him.

I`ve been advised to buy a new clutch pack,but before i do,has anyone had the same problem??,i know about measuring the plates etc,but i`ve been told that it could be the `o`ring behind the top hat thingy behind the casing thats worn.

The lever is nice and light,clutch operation is smooth,and yes i have back bled the clutch from the casing.

Another thing is that although its dragging when lever is pulled back to the bars,the biting point is in what i would say is a normal position.

Got any tips???

Thanks in advance

[3006phil]

Hi chaps,i need to sort this dragging clutch out on my sons bike.its not a major problem but i just want it right for him.

I`ve been advised to buy a new clutch pack,but before i do,has anyone had the same problem??,i know about measuring the plates etc,but i`ve been told that it could be the `o`ring behind the top hat thingy behind the casing thats worn.

The lever is nice and light,clutch operation is smooth,and yes i have back bled the clutch from the casing.

Another thing is that although its dragging when lever is pulled back to the bars,the biting point is in what i would say is a normal position.

Got any tips???

Thanks in advance

DOES YOUR LEVER NOT HAVE AN ADJUSTING SCREW BUILT INTO IT. YOU CAN NORMALY SORT JUST BY SCREWING THISIN A FEW TURNS. ALSO! ARE YOU RUNNING THE GEAR BOX ON 'LIGHT GEAR OIL' FULLY SYNTHETIC?????

[jse]

Hi chaps,i need to sort this dragging clutch out on my sons bike.its not a major problem but i just want it right for him.

I`ve been advised to buy a new clutch pack,but before i do,has anyone had the same problem??,i know about measuring the plates etc,but i`ve been told that it could be the `o`ring behind the top hat thingy behind the casing thats worn.

The lever is nice and light,clutch operation is smooth,and yes i have back bled the clutch from the casing.

Another thing is that although its dragging when lever is pulled back to the bars,the biting point is in what i would say is a normal position.

Got any tips???

Thanks in advance

A little drag is generally normal in the Gas-Gas clutch and actually works to your advantage in that it keeps the driveline "loaded" so that you don't have a jerky clutch engagement when all the slack is taken out of the chain, gears, clutch plate fingers etc. Though it does make finding Neutral a pain when stopped or pushing the bike in gear out of the section with a dead engine (with which my riding talent level demonstrates all too often).

I'd measure the clutch pack first before replacing it, the assembled pack should be about 9.75mm thick and the clutch fingers should be around 17/17.5mm in height above the basket hub (see: http://www.trialspartsusa.com/diagrams/Pro...12th%202007.doc ).

The 03' uses an o-ring and seal on the servo cylinder post down at the clutch sidecover (the 02', like mine, has two o-rings) and if they were leaking I would guess you would probably see a loss of fluid in the M/C reservoir, unlike a leaking seal in the M/C, which would just pass fluid back up to the reservoir.

Jon

[ikb]

And as recomended on the Trials parts USA link use Dexron III ATF its nice and cheap so you can change it regularly

[jse]

And as recomended on the Trials parts USA link use Dexron III ATF its nice and cheap so you can change it regularly

I run a General Motors product (AutoTrac II transfer case fluid) in my 02' 280 Pro with good results and recommend it to riders with 02' to 05' Pros. The late models seem to do a little better with the DexronIII ATF, which has a little more "bite", as the Bellville spring in the clutch is a little thinner for lighter lever pressure. The ATF is about 7.5 weight and the Gas-Gas clutches seem to feel better with a lighter fluid. I change mine about 5-10 hours, or less, of use or after a tough or wet Trial. It's a little more critical to keep fresh tranny fluid in a Pro as the main crank bearings are lubed by the transmission oil. I also run a magnet type drain plug (like the lower crankcase plug) in the top sidecover to give extra protection from swarf.

Jon

[dabomb]

Thanks for the replies,i`m running on dextron 3 already.The adjustment screw doesnt change the the clutch,there`s not much you can do with that anyway beacause you have to have it so that the piston is released fully when you let go of the clutch lever,if it doesnt it can cause other problems i am told.

I will measure the clutch thickness and start from there.I will also change the o ring and seal just to eliminate it.

Cheers

[dabomb]

A little drag is generally normal in the Gas-Gas clutch and actually works to your advantage in that it keeps the driveline "loaded" so that you don't have a jerky clutch engagement when all the slack is taken out of the chain, gears, clutch plate fingers etc. Though it does make finding Neutral a pain when stopped or pushing the bike in gear out of the section with a dead engine (with which my riding talent level demonstrates all too often).

I'd measure the clutch pack first before replacing it, the assembled pack should be about 9.75mm thick and the clutch fingers should be around 17/17.5mm in height above the basket hub (see: http://www.trialspartsusa.com/diagrams/Pro...12th%202007.doc ).

The 03' uses an o-ring and seal on the servo cylinder post down at the clutch sidecover (the 02', like mine, has two o-rings) and if they were leaking I would guess you would probably see a loss of fluid in the M/C reservoir, unlike a leaking seal in the M/C, which would just pass fluid back up to the reservoir.

Jon

Hey thanks for the link about the clutch.Every thing checks exept...

1/ The 17/17.5 is only 15mm

2/ The info says insert the thickest fibre plate first,but they are all the same....Isuppose this means new clutch pack then??

[jse]

Hey thanks for the link about the clutch.Every thing checks exept...

1/ The 17/17.5 is only 15mm

2/ The info says insert the thickest fibre plate first,but they are all the same....I suppose this means new clutch pack then??

Not necessarily, some packs came with first (inner) fiber plate as a thickness adjustment plate and the two steel plates were 1.6mm. There was supposed to be a 1.8mm plate available to adjust that type of pack for wear but we haven't been able to get them over here so far.

The clutch packs are adjustable for thickness (which dictates finger height) so you should be able to substitute steel plates of other thickness' to set it to the desired pack thickness. The steel plates (or "shims" as they are sometimes called) come in 1.3, 1.4, 1.5, 1.6mm and supposedly the 1.8mm measurements and you can get them from your dealer.

I've tried to discover a stable linear relationship between substituted change in plate thickness and change in finger height ("If I substitute a 1.5mm shim for a 1.4mm shim in the clutch pack, it will change the assembled clutch finger height "X" amount") but I haven't found one. It's a change shim, assemble clutch, measure finger height, swear and repeat process sometimes.

Jon

[dabomb]

Not necessarily, some packs came with first (inner) fiber plate as a thickness adjustment plate and the two steel plates were 1.6mm. There was supposed to be a 1.8mm plate available to adjust that type of pack for wear but we haven't been able to get them over here so far.

The clutch packs are adjustable for thickness (which dictates finger height) so you should be able to substitute steel plates of other thickness' to set it to the desired pack thickness. The steel plates (or "shims" as they are sometimes called) come in 1.3, 1.4, 1.5, 1.6mm and supposedly the 1.8mm measurements and you can get them from your dealer.

I've tried to discover a stable linear relationship between substituted change in plate thickness and change in finger height ("If I substitute a 1.5mm shim for a 1.4mm shim in the clutch pack, it will change the assembled clutch finger height "X" amount") but I haven't found one. It's a change shim, assemble clutch, measure finger height, swear and repeat process sometimes.

Jon

Thanks jon,but the clutch pack measures the correct size,IE 9.8mm,so why is the 17mm measurement so far out??

[spenser]

Thanks jon,but the clutch pack measures the correct size,IE 9.8mm,so why is the 17mm measurement so far out??

My two cents are: The clutch pack measurement doesn't include the spring or pressure plate but for the correct operation of the clutch I have found that the 17-17.5 mm finger height is the most important for engagement. If the finger height is too high the clutch may not fully engage (slipping in taller gears) and if too low it may not disengage properly. I hope that this helps

Spencer

[jse]

My two cents are: The clutch pack measurement doesn't include the spring or pressure plate but for the correct operation of the clutch I have found that the 17-17.5 mm finger height is the most important for engagement. If the finger height is too high the clutch may not fully engage (slipping in taller gears) and if too low it may not disengage properly. I hope that this helps

Spencer

Spencer,

That also is my experience. The clutch pack thickness is just an initial adjustment I can do to get me in the ballpark for the required measurement for the finger height. That "top hat" servo cylinder has a limited range of free movement before it runs into something (like just about everything else in an engine) and although, in operation, it does not move far, I like to keep it near the center range of motion, which seems to give me the smoothest emgagement.

Jon

[dabomb]

Spencer,

That also is my experience. The clutch pack thickness is just an initial adjustment I can do to get me in the ballpark for the required measurement for the finger height. That "top hat" servo cylinder has a limited range of free movement before it runs into something (like just about everything else in an engine) and although, in operation, it does not move far, I like to keep it near the center range of motion, which seems to give me the smoothest emgagement.

Jon

so what are we saying,make the clutch pack smaller so i can achieve the 17/17.5mm??.Will it not go out of tollerance??

[jse]

so what are we saying,make the clutch pack smaller so i can achieve the 17/17.5mm??.Will it not go out of tollerance??

Well, I could be wrong (which my wife would quickly assure me that it is NOT the first time...., but in my experience, the assembled clutch finger height, that is dependent on the operating pressure of the plate/Bellville spring, and the condition/relationship of the mechanical parts-not just the measured free thickness of the clutch pack outside of the clutch assembly-is a more relevant measurement. I find I get better results by setting the finger height as my "final answer", irregardless of what the free clutchpack measurement is.

So, yea, I'd say try a .1mm thinner shim plate and see how the fingers are. Rarely, but sometimes the fiber plates will swell a little over time, which will expand the pack and drop the fingers down to the point where the clutch will be stiff at the lever. I did one this morning for a friend who rides Expert Class and is hard on clutches. It was easy to adjust and works like new. The Pro engines are quite simple, but quite precise.

Jon

[peterb]

Hi Jon and Spencer,

I have found that when the clutch plates swell (usually with coolant getting into the gearbox oil), the small increase in pack height is sufficient to create a problem with the clutch operation, where the actuation is heavy, seemingly insufficient throw of the clutch lever and a dragging clutch when disengaged.

The small increase in the clutch pack causes the 10 operating fingers to move to a position beyond a decent mechanical advantage, and therefore requiring more movement from the slave piston, as Jon said, the significant measurement is the finger height, best around 17mm.

An inexpensive fix, is to carefully ease off the fibre plate thickness using emery paper on top of a sheet of thick (flat) glass and get the pack down to about 9.75mm.

Bye, PeterB.

[jse]

Hi Jon and Spencer,

I have found that when the clutch plates swell (usually with coolant getting into the gearbox oil), the small increase in pack height is sufficient to create a problem with the clutch operation, where the actuation is heavy, seemingly insufficient throw of the clutch lever and a dragging clutch when disengaged.

The small increase in the clutch pack causes the 10 operating fingers to move to a position beyond a decent mechanical advantage, and therefore requiring more movement from the slave piston, as Jon said, the significant measurement is the finger height, best around 17mm.

An inexpensive fix, is to carefully ease off the fibre plate thickness using emery paper on top of a sheet of thick (flat) glass and get the pack down to about 9.75mm.

Bye, PeterB.

That would work just about as well as replacing shims as it wouldn't take more than a little off the fiber faces to slim down the pack. My buddy's 06' 300 Pro had the fibers swell a little, just enough to move the fingers down to about 14mm. He was sure he needed a new clutch pack, but replacing a shim made it good as new. The fibers were in excellent shape, but the measurements are so exact in the Pro clutch, it won't tolerate things too far out of wack. The cool thing about the Pro clutch is that it's fairly easily adjusted to suit one's riding style as far as engagement is concerned.

Jon