Triumphrat

01-02-2006

The screw heads in my front-brake master cylinder cap are knarled and torn, as such I can't remove them !
How should I get them out and with what size bolt should I replace them ?
I'll need to get the bolts ready in anticipation of getting the cap off !
Please help ?

MickMaguire · 01-02-2006

you need to carefully drill off the heads - they are a countersunk screw. Once yopu have the cover off you will be able to grab hold of the rest of the screw with some locking grips (or similar) and wind them out

I cant remember the exact size off the top of my head but they are metric 4, 5mm at a guess. Get stainless replacements and use a smear of anti seize (copaslip etc) on them - don't get it in the brake fluid though.

[ This message was edited by: MickMaguire on 2006-01-02 09:43 ]

dazco · 01-02-2006

I've successfully done this many times with the following method, but be warned you could scratch the cover if not carefull. take a small regular screwdriver and hold it against the slot near the edge of the screw and tap it with a hammer till it breaks loose. In this situation make sure to keep the driver so that it's not TOO parallel to the cover. Keep a pretty steep angle to keep it from slipping out of the slot and scratching the cover. Done right you won't, but again you gotta use common sense and be carefull. I never have that problem having done this many times, but you've been warned.

A screwrdriver thats good and sharp or some such other tool will get a good bite and with a steep angle won't slip.Thats the trick.....to get good enough bite so it doesn't slip and gives a solid bite that will crack it loose. And just tap it, don't crank it hard. You'd be suprised at how such stubborn screws will often break loose pretty easily with a few taps.

dazco · 01-02-2006

I should have also mentioned that if you can create a deeper area with a dremel or such it's even better. A divot near the edge thats deep enough will give a more stable place for the tool without as much chance of slipping. Of course if you use a dremel you also have to be carfull not to let the bit slip ! But however you do it a deeper place to put the tool will be that much better.

relocatedfixer · 01-02-2006

Hello there.
I read with interest the replies so far. Speaking as an engineer, whenever I encounter the ' stuck screw/bolt etc ' problem, I always try to tighten the offending item. This can break the seal that has formed in the thread and once broken, despite having been tightened, the offending item is usually removable. In my experience, the screw head is usually damaged more in the anti-clockwise direction ( on a right-hand thread ) and there is enough purchase left on the head in the clock-wise direction to enable some grip. Another thing worth trying if the screws are cross-points, is to find a suitable sized flat-bladed screwdriver and using a hammer or mallet, tap a new slot into the screw head. I have done, and still do, these things and it has saved many a ' situation '. There is nothing worse than spending ages skinning knuckles and scratching previously good metalwork when you thought it would be so simple. You have my sympathy and encouragement. Good luck.
RF.

01-02-2006

Thanks to everybody for their help. I'll give them a try. What's concerning me is getting the correct size replacement bolts ready in place so that when the cover comes off and the fluid goes in, I can seal it properly.

Thanks very much for everybodys help.

relocatedfixer · 01-02-2006

You'll probably find that you can re-use the originals, temporarily, until some new ones are sourced. Just remember to coppaslip the threads first. Try asking your local bike shop or an engineering supplier or perhaps a breakers? for some screws.
RF.

Slinky · 01-02-2006

I think they are M5x15 CSK, but check first.

Call "Custom Fasteners" on 01686 629666 and you can get some Allen head, stainless steel replacements delivered next day.

I have been buying from them for years and they are excellent peopleto deal with.

The screws will set you back about 20p each! Ask them to send you a free catalogue too.

Avatar · 01-02-2006

Same thing happened to me. The screws cost maybe 10 cents each.

From one of my previous posts:
"Here are some lessons I learned:
...
Don't tighten the master cylinder's screws too tight. One got
stuck and I couldn't get it out. I ended up having to use a left
handed drill bit to remove it. I replaced them with M5-16mm stainless
sunk screws from the hardware store."

01-19-2006

one tip that works great is to get a slightly smaller socket than the worn head, hammer it on!

you'll get one or if your lucky two, more tries outta that!! :wink: