Hesketh Owners Club Forum

Hesketh Helpline => Requests for Help and (Hopefully) Answers => Topic started by: Chris N on December 28, 2019, 03:28:18 PM

Title: clutch slave cylinder
Post by: Chris N on December 28, 2019, 03:28:18 PM
hi all
i thought the clutch took a lot more lever pressure than my other bikes so a while ago ordered a set of seals and having not a lot to do today started to change them.
once the casing screws were removed the casing came off easily.taking the covers off the clutch cylinder oddly the piston return spring was on the outside of the cylinder unlike the workshop manual diagram which shows it on the inside,
the piston and cylinder was in a bit of a mess and the cylinder would not budge so i left it where it was.
the cylinder wall marks have cleaned up completely and everything has had an ultrasonic bath.
the piston has a new seal part 74269 from the parts center ltd on ebay and a new o ring.
the inner end case oil seal was changed.
oil seal 10x18x5_sc_vi  and o ring bs024 came from simpley bearings.
if someone can confirm if the parts diagram is correct for the spring position ,or if it even matters i will pop it all back together.
Title: Re: clutch slave cylinder
Post by: velocollins on December 31, 2019, 07:42:22 AM
Hi Chris,
I completely overhauled my Slave Cylinder earlier in the year as 38 years of DOT 4 and moisture and sludge had badly scored the cylinder wall and it was not possible to polish out.
I fitted all new seals and cylinder and new piston.  The reason for changing the piston was because the ball bearing in the bottom of piston that is used to reduce friction had fused in to the piston and it would not come out without machining.
I would check the ball bearing in your piston as in my opinion this was one of the primary reasons the clutch was stiff.
On the end on the pushrod there was also a significant dent and I ground this out which made a difference.
The piston spring was definitely on the outside when I dissembled my unit and I have attached a copy of the original Hesketh Engineering drawing that shows the spring item 25 on the outside.

Hope this helps.

When my clutch failed as the clutch adjusting screw fractured the piston bottomed out and the weak link was the outer cover seal and I noticed yours looks a bit the worse for wear.  I recommend you replace the cover seal with suitable material.
Title: Re: clutch slave cylinder
Post by: Chris N on December 31, 2019, 08:12:33 AM
hi Richard
thanks for the reply this is the diagram i was looking at,i was surprised when the ball bearing came out of the cylinder as its shown on the clutch end of the rod not the piston.
Title: Re: clutch slave cylinder
Post by: velocollins on December 31, 2019, 12:01:55 PM

Hi Chris,

It appears the size of the engineering file is too large to load so I have sent to your e-mail.

The drawing shows the spring in the position you marked up on the drawing on the outside.


Title: Re: clutch slave cylinder
Post by: Chris N on December 31, 2019, 01:47:26 PM
thanks for that,
so the original drawing if different from the diagram in the workshop manual.
in the position of the spring and ball bearing.
Title: Re: clutch slave cylinder
Post by: REMF on January 01, 2020, 12:01:44 PM
The correct place for the spring is where you found it - ignore the diagram, it is wrong.
I reassembled my clutch some years ago and had all sorts of problems. Eventually I phoned Mick Broom who asked "Why are you following the manual?"
Title: Re: clutch slave cylinder
Post by: Chris N on January 01, 2020, 01:36:19 PM
thanks for that,i should have known.
Title: Re: clutch slave cylinder
Post by: Chris N on February 04, 2020, 02:45:26 PM
having done the work on the slave cylinder the clutch pull was still heavy and a bit notchy with dark fluid coming back into the reservoir on each pull turning the fluid black with rubber bits so all was not good.
i ordered another new brembo master cylinder piston kit and a new clutch pressure line but longer so it could be routed around the rear cylinder and not along the frame tube to clean up the look a bit.
HEL Performance order no 111788.
disapointingly having changed both things saw no improvement in the clutch action so i dug out the bikes original brake master cylinder which had got damaged in transit getting the bike to me from the uk
(something that still annoys me when i think about it).
removing the original and new piston and comparing them side by side the problem became clear.
basically new stuff is rubbish compared to the original.
on a brake the difference is not noticeable due to the relatively short stroke distance but on the clutch where its almost going the whole travel not having as good wall contact and possibly not moving squarely in the bore must make all the difference.
so the old piston went in and the clutch is now a smooth notch-less lighter joy to use.