I'm trying to take off the rear brake master cylinder of my sherco 125 2007 but the bolts won't budge so was wondering whether they where a left haned thread or if not what is the best way of getting it off I have cover them with wd 40 and it didn't work.

I doubt it is left hand thread, Usually that is done for safety purposes on things that can rotate during usage

My Betas have a nut on the back side not threaded into the master

Hi

Dont worry the screws arent left hand thread. If they are standard they'll be a button head screw that takes a reasonably small allen key.

As you are aware the danger is rounding off the hex socket in the fastener. I suggest the following as a procedure.

• Get a friend to help you
  
• Find a centre punch and small hammer. Ensure that the centre punch point is defined but not overly sharp.
  
• One person applies a reasonable torque with the allen key
  
• The second person takes the punch and heavily taps the fastener head in the correct direction. Try to apply the punch to the outer part of the fastener head (more torque is applied).
  
• The combination of the two forces will shift it if it can be shifted.
  

If the above fails there are two other techniques but they get more drastic.

1. Get a jewlers gas torch (tiny flame) and heat the fastener head to try to use expansion to break the seized surfaces. The fastener needs to reach 200-250 degrees but NOT cherry red.
   
2. Grind the head off the screws to remove the master cyl. Heating the "sticking out" portion of the screw is now easy and some mole grips or a vice can be used to turn the screw shaft.
   

Dom

Edited December 19, 201213 yr by dombush

Thanks for that it has come off I have been knocking at it all morning with it covered in wd40 and tonight it just came off with some force but thanks.