Clutch Problems Help Required
Posted: 27 Apr 2014, 22:38
After about 10 hours in the man cave over the last 2 days with little success I m in need of some help.
The plan was to fit a Sigma Slipper Clutch and Brembo RCS 16 Clutch M/C to my 2004 Honda SP2. With hindsight perhaps I should have fitted these separately and got each system working individually but being short of time I didn’t and decided to fit both at the same time.
Fitting of the slipper clutch went well. All friction plates were like new and within the tolerance of new plates so no point in replacing. I checked the metal clutch plates for warping and they were all perfectly flat. The only things I did decide to replace were the clutch springs as these were worn (but still within limits) so a set of 6 OEM Honda springs were sourced and fitted as a precaution. The fitting of the slipper clutch went well with no problems and all settings were within tolerance recommended and I even phoned Neil Spalding of Motogp fame to check my settings (He owns Sigma Performance) who confirmed all was good.
Next task was to fit the Brembo 16 RCS Clutch Master Cylinder and all went well with this or so I thought until I tested the completed set up and found the clutch is not disengaging correctly.
Basically with the bike up on the Abba stand and rear wheel in the air I put the bike in gear (engine off) pulled the clutch in and tried to turn the back wheel by hand. It was possible to turn the back wheel but only by exerting a reasonable amount of force so I think the clutch is not disengaging the plates enough and therefore dragging. For info I tried the same test on my Fireblade and the back wheel turns easily when in gear with the clutch pulled in. I put a DTI on the end of the clutch rod to see how much the pressure plate moves when the clutch lever is fully pulled in and found I have 0.7mm of travel which although I have no specific value I m trying to attain (figure unknown) this seems too small. (Note: I found some info on the internet that suggests the travel should be equal to one clutch plate’s thickness so in this case that would equal 2mm but I don’t know how good this info is)
I stripped the Sigma slipper clutch to check everything was put back together as per the manual and confirmed this was correct.
Next I thought I'll take the slave cylinder off and see how much the slave cylinder moves when the clutch lever is fully pulled in and I got the same value of 0.7mm. This proved to me that the problem is not with the Sigma slipper clutch as it is free to move and the amount of travel at the slave clyinder is equal to amount at the pressure plate so no travel is lost within the actual clutch unit if that makes sense. In my opinion its just that the slave cylinder is not moving enough (0.7 mm) to open up the clutch plates in the stack to disengage fully.
As the Brembo 16 RCS has a 16 mm piston and the OEM Honda master cylinder piston is 12.7 mm diameter I thought to myself is the Brembo RCS master cylinder not moving enough fluid to move the slave cylinder and subsequent clutch pressure plate by the correct amount. I don't think this is the case as A, Brembo recommend the 16mm RCS for my specific bike and B the Brembo RCS Master cylinder piston is larger than stock therefore if anything it will move more fluid so in theory the slave cylinder should move more or the same amount for less travel at the lever.
Therefore after trying all the above I m assuming the problem is air in the clutch line which means I m not displacing enough fluid out of the Clutch master cylinder to move the slave cylinder by the correct amount. I have checked for leaks and cannot find any. I have tried bleeding at the slave cylinder bleed nipple and the nipple on the Bremo RCS. I have tried injecting DOT 4 clutch fluid at the slave cylinder to reverse fill the system as well as the traditional method of filling at the reservoir by the clutch lever and bleeding the system down at the slave cylinder bleed nipple. I have removed the slave cylinder and tried pumping this by hand to displace the air to the high point at the Fluid reservoir. Trying all the above I have managed to move some air but as the travel is to little at 0.7 mm I think I still have some air in the system but bugger me if I can’t get it out. Note for info although the clutch lever is not spongy it does seem a little lighter than I would expect so this also helps confirm my theory of air in the system being the cause of the problem.
In short I have tried everything I can possibly think of with no success and therefore I m looking for some help from someone with more experience on the subject.
Do people agree its most likely air trapped in the system or could it be something I have over looked ?
Any comments or suggestions are most welcome. Thanks and hope some one can help.
The plan was to fit a Sigma Slipper Clutch and Brembo RCS 16 Clutch M/C to my 2004 Honda SP2. With hindsight perhaps I should have fitted these separately and got each system working individually but being short of time I didn’t and decided to fit both at the same time.
Fitting of the slipper clutch went well. All friction plates were like new and within the tolerance of new plates so no point in replacing. I checked the metal clutch plates for warping and they were all perfectly flat. The only things I did decide to replace were the clutch springs as these were worn (but still within limits) so a set of 6 OEM Honda springs were sourced and fitted as a precaution. The fitting of the slipper clutch went well with no problems and all settings were within tolerance recommended and I even phoned Neil Spalding of Motogp fame to check my settings (He owns Sigma Performance) who confirmed all was good.
Next task was to fit the Brembo 16 RCS Clutch Master Cylinder and all went well with this or so I thought until I tested the completed set up and found the clutch is not disengaging correctly.
Basically with the bike up on the Abba stand and rear wheel in the air I put the bike in gear (engine off) pulled the clutch in and tried to turn the back wheel by hand. It was possible to turn the back wheel but only by exerting a reasonable amount of force so I think the clutch is not disengaging the plates enough and therefore dragging. For info I tried the same test on my Fireblade and the back wheel turns easily when in gear with the clutch pulled in. I put a DTI on the end of the clutch rod to see how much the pressure plate moves when the clutch lever is fully pulled in and found I have 0.7mm of travel which although I have no specific value I m trying to attain (figure unknown) this seems too small. (Note: I found some info on the internet that suggests the travel should be equal to one clutch plate’s thickness so in this case that would equal 2mm but I don’t know how good this info is)
I stripped the Sigma slipper clutch to check everything was put back together as per the manual and confirmed this was correct.
Next I thought I'll take the slave cylinder off and see how much the slave cylinder moves when the clutch lever is fully pulled in and I got the same value of 0.7mm. This proved to me that the problem is not with the Sigma slipper clutch as it is free to move and the amount of travel at the slave clyinder is equal to amount at the pressure plate so no travel is lost within the actual clutch unit if that makes sense. In my opinion its just that the slave cylinder is not moving enough (0.7 mm) to open up the clutch plates in the stack to disengage fully.
As the Brembo 16 RCS has a 16 mm piston and the OEM Honda master cylinder piston is 12.7 mm diameter I thought to myself is the Brembo RCS master cylinder not moving enough fluid to move the slave cylinder and subsequent clutch pressure plate by the correct amount. I don't think this is the case as A, Brembo recommend the 16mm RCS for my specific bike and B the Brembo RCS Master cylinder piston is larger than stock therefore if anything it will move more fluid so in theory the slave cylinder should move more or the same amount for less travel at the lever.
Therefore after trying all the above I m assuming the problem is air in the clutch line which means I m not displacing enough fluid out of the Clutch master cylinder to move the slave cylinder by the correct amount. I have checked for leaks and cannot find any. I have tried bleeding at the slave cylinder bleed nipple and the nipple on the Bremo RCS. I have tried injecting DOT 4 clutch fluid at the slave cylinder to reverse fill the system as well as the traditional method of filling at the reservoir by the clutch lever and bleeding the system down at the slave cylinder bleed nipple. I have removed the slave cylinder and tried pumping this by hand to displace the air to the high point at the Fluid reservoir. Trying all the above I have managed to move some air but as the travel is to little at 0.7 mm I think I still have some air in the system but bugger me if I can’t get it out. Note for info although the clutch lever is not spongy it does seem a little lighter than I would expect so this also helps confirm my theory of air in the system being the cause of the problem.
In short I have tried everything I can possibly think of with no success and therefore I m looking for some help from someone with more experience on the subject.
Do people agree its most likely air trapped in the system or could it be something I have over looked ?
Any comments or suggestions are most welcome. Thanks and hope some one can help.