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  #51  
Old 08-02-18, 08:54
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we faffed around lots with the hydraulic system and just gave up...I "think" there are numerous pushrod lengths and I "think" you can over throw the clutch if the travel is too long - I could be talking bollox....either way, our mechanical connection has proved bombproof....famous last words
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  #52  
Old 08-02-18, 10:49
asklepios asklepios is offline
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u01rsb I am running a K4 which originally was cable ,with a later hydraulic. The plates fit, but the push rods are different by several mm. That can lead to the slave /cylinder over throwing ,bottoming out and stretching the threads holding the slave to the plate. This little bit of slack can give unreliable action. That said I would certainly change the seals.
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  #53  
Old 08-02-18, 13:58
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I run a K3/4 which has always been cable operated as on the donor bike and apart from adjustment issues in the early days works fine. I have to replace the cable inner every few years.

Why then does the hydraulic system work reliably on the bikes but not cars.
Is it related to the relevant heights of master / slave cylinders?
The bike master cylinder is higher than the slave and will put a pressure of a couple of Ft Head of fluid into the system.
The car master cylinder is approx the same height as the slave so that there is no static pressure in the system. Would this allow the ingress of air bubbles?
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  #54  
Old 08-02-18, 14:05
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I expect that it may have to do with the length of tubing between the pedal piston to the slave piston on the engine. Within this overall length there is likely to be a higher volume of trapped air that can be compressed and potentially why the slave cylinder doesn’t move as much as it should.

I'm going to try and get a new seal kit for the slave cylinder, a new actuator rod, bleed it thoroughly and then see if that works...

fingers crossed...
...
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  #55  
Old 08-02-18, 14:18
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Andy and you could question why the brake system is not similarly effected. The slave cylinder being higher than the master should send air there....but is doesn't. That said the experiences of others is interesting.

U01 IIRC. None of the standard push rods are quite right and you may have to fit a v small spacer. As the movements of the clutch are small this hints why the adjustability, fine tuning if you like ,of the cable system is attractive. My experience is once the geometry in the hydraulic is correct it works well.

Last edited by asklepios; 08-02-18 at 14:20. Reason: Autocorrects spelling
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  #56  
Old 08-02-18, 14:28
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Very true. If the relevant heights was found to be the problem you can just imagine the scrutineering problems when all the hydraulic clutch cars appeared with remote reservoirs on top of the roll hoop.
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  #57  
Old 08-02-18, 16:46
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Could the issue not be more simplistic in the fact that people tend to buy soley engines from a bike breaker and do not generally have the complete bike with master cylinders for reference?

The car clutch pedal ratio may also be the culprit if not an exact match to the bike handlebar lever ratio
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  #58  
Old 08-02-18, 17:03
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If you get the right amount of operating shaft travel then the ratios must be correct. Also you can get a good feel for the correct amount of travel from setting clearance when disengaged and the amount of pedal travel required to get partial and full engagement. There has been a lot of pots on that already.

Even with the cable arrangement you have to go through something similar initially, setting the operating lever gap and moving the cable pedal end fixing point closer to, or further from the pedal pivot to get a comfortable operating point, which is the hydraulic equivalent of reducing or enlarging the master cylinder bore (but cheaper).
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