Pro Clutch Lightening...help Required

[dabomb]

Has any body had problems with a heavy clutch on the gasgas pro?,my sons clutch is quite heavy,especially for a youngster.I recently installed a new clutch,I believe it is possible to make it lighter by adjusting the thickness of the clutch pack using different size shims.Has anybody tried this?,also is DOT 4 the correct fluid??

Cheers in advance.

[dickielumpkin]

When my son first started out on a Gasgas Pro I took half of the clutch springs out to begin with. Obviously depends what sort of riding he wil be doing but there was never a problem with clutch slip. Might be worth a try until strong enough to use all springs.

Regards

Andy

[dabomb]

Thanks mate,that is something i would definatly do but the pro clutch i different than most clutches(you sure your lad had a pro?).It has `fingers`and a belville spring which cannot be messed with.Changing the metal plates is the only way i think.

Must be someone out there that can help me

[dan williams]

Lighter pro clutch spring

http://www.jackscycles.com/accesories.html

[dabomb]

That looks interesting,wonder if you can get them over here??,i will check it out.

[telecat]

If you have used DOT4 on a Gas Gas Pro you are in trouble!!!!!!!!!!!!!!!!!! They use the same fluid as Citroen Hydrolastic suspension in the clutch system, it's called LHM, and it's Green!!!! Use DOT4 and you will find the seals will perish allowing the fluid into the clutch meaning you'll need another clutch.

The easiest way to make the clutch lighter is to replace the "small" Reservoir on the lever end with a standard sized one. We got one from BVM. It even comes with the "Green" lid that indicates the use of LHM fluid.

Another method is to use the "S3" clutch cover. It's much more expensive though.

[dabomb]

If you have used DOT4 on a Gas Gas Pro you are in trouble!!!!!!!!!!!!!!!!!!

You got me worried there for a minute,the bike in question is an `03,the mineral oil issue came in `05 acording to the gasgas tachnical bulitin i have just read.It also states DOT 4 on the M/S cap.

I think this bike already has the larger resevoir on,that must be another change they made after `03

Edited April 30, 2008 by dabomb

[jse]

"If you have used DOT4 on a Gas Gas Pro you are in trouble!!!!!!!!!!!!!!!!!!"

You got me worried there for a minute,the bike in question is an `03,the mineral oil issue came in `05 acording to the gasgas tachnical bulitin i have just read.It also states DOT 4 on the M/S cap.

I think this bike already has the larger resevoir on,that must be another change they made after `03

The 03' takes DOT-3/4/5.1 brake fluid and differs, in part, from the 02' in that it uses an o-ring and seal in the clutch servo cylinder, rather than the double o-ring setup and the sidecover material is aluminum, not magnesium.

Although a new clutch pack will usually measure about 17.5mm in finger height, it might be a good idea to check the installed height on your bike (the shorter finger heights will tend to make the lever harder to pull). Since you're down there, you might want to convert the clutch fluid to DOT-5 (Silicone), which usually gives a smoother pull at the lever. You'll need to remove, clean the internals of the master cylinder and servo cylinder, flush and blow out the line with compressed air and pre-bleed the servo cylinder (hold sidecover "upside down" and press on servo cylinder to get air out of that area). If the servo cylinder is reluctant to move easily, the o-ring on the tower may have swollen and replacing that will ease the lever pull.

Mineral oil seals will usually be green in color, DOT-3/4/5.1 will be black. DOT-5 is compatable with both types of seals, since Silicone is essentially inert. However, the three types of fluids do not mix, in spite of what you may have read or been advised.

Jon

[dabomb]

The 03' takes DOT-3/4/5.1 brake fluid and differs, in part, from the 02' in that it uses an o-ring and seal in the clutch servo cylinder, rather than the double o-ring setup and the sidecover material is aluminum, not magnesium.

Although a new clutch pack will usually measure about 17.5mm in finger height, it might be a good idea to check the installed height on your bike (the shorter finger heights will tend to make the lever harder to pull). Since you're down there, you might want to convert the clutch fluid to DOT-5 (Silicone), which usually gives a smoother pull at the lever. You'll need to remove, clean the internals of the master cylinder and servo cylinder, flush and blow out the line with compressed air and pre-bleed the servo cylinder (hold sidecover "upside down" and press on servo cylinder to get air out of that area). If the servo cylinder is reluctant to move easily, the o-ring on the tower may have swollen and replacing that will ease the lever pull.

Mineral oil seals will usually be green in color, DOT-3/4/5.1 will be black. DOT-5 is compatable with both types of seals, since Silicone is essentially inert. However, the three types of fluids do not mix, in spite of what you may have read or been advised.

Jon

Thanks Jon,i will check all these things out.Just for reference,do you know how much (for example)a .05mm alteration of the clutch pack will affect the finger height??

[jse]

Thanks Jon,i will check all these things out.Just for reference,do you know how much (for example)a .05mm alteration of the clutch pack will affect the finger height??

You could probably come up with a rough formula, but the problem is, due to the design of the leverage point, the relationship of pack thickness to finger height change is not a linear constant and depends on the starting point. The adjustment plates come in 1.3, 1.4, 1.5, 1.6 and 2.0mm in most cases (there's supposed to be a 1.8mm available but I've never seen one). Some riders sand the fiber plates, but that is a "one-way-street" and if you go too far, it could be a problem.

The "final answer" appears to be the actual finger height measurement after the clutch is assembled.