Rear Master Cylinder Screws

[Codey90]

Hi All,
Having an issue with two screws on my rear Master brake cylinder. They are barely accessible due to a part of the frame running above the top of it. I've tried an offset screwdriver but they don't fit very well even after trying four sizes.
The screws, as you can also see are rusted and very difficult to turn using a bit in a wrench without potentially stripping them. I've left them to soak in WD40 overnight and am tempted to try an impact screwdriver but the only way would be to use the driver at an angle due to the frame obstructing a perpendicular fit. Any other ideas?

https://imgur.com/a/GBjgqX7

[Riejufixing]

Can you warm it up a bit? Either directly, or with a bit of metal bar that you can heat up hot and apply to the screw heads? It's probably (guess) just stuck at the "countersink".

Edit: You said: "very difficult to turn using a bit in a wrench without potentially stripping them". Do you mean that they do actually turn, but are stiff? If so, WD40 is crap, try "Plus gas" or similar.

[Codey90]

[NJD]

What bike is it?
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[Codey90]

[NJD]

Disconnect brake light switch and then undo the two mounting bolts and see if you can wiggle it to a position to get easier access to the screws?

I have to undo my rear m/c mounting bolt to fill it up (cbf1000) so not an uncommon issue.

https://i.postimg.cc/GtvG4BY9/cylinder.jpg

Bunch of spares for that bike from above seller:

https://www.ebay.co.uk/sch/m.html?_odkw=&_ssn=browniesbikes&_armrs=1&_osacat=0&_from=R40&_trksid=p2046732.m570.l1313.TR10.TRC0.A0.H0.Xzsx-f.TRS0&_nkw=zsx-f&_sacat=0
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The do it all, T̶h̶e̶ ̶b̶r̶o̶k̶e̶n̶ ̶o̶n̶e̶,̶ ̶T̶h̶e̶ ̶b̶i̶g̶ ̶l̶u̶m̶p̶,̶ ̶C̶h̶o̶n̶g̶ ̶N̶o̶o̶d̶l̶e̶

[Kawasaki Jimbo]

Can you use a punch to turn the screws and break them free of the corrosion?

[Riejufixing]

[Codey90]

Thanks for all the replies guys. Ill try chasing it out with a small punch, never thought of that. In terms of heating it up I've just had a look through the kitchen and my partner has one of those electric candle lighter things for her overpriced collection of Yankee candles so I may try that too. If all else fails it may just be a case of taking the mounting bolts off and wiggling it about a bit for a better angle as mentioned. Would have thought the process would have been much simpler than what it's turned out to be.

[stinkwheel]

They are JIS screws. You can tell by the little "dent" to one side of the cross. If you don't have a specific JIS screwdriver, you wont get them out without stripping the heads regardless of how well you can get at them. Phillips or posidrive will not fit properly. I've never seen a right angle JIS driver.

Sometimes filing the tip down a few mm on a phillips scredriver will take it closer to fitting a JIS. If the bike came with a toolkit (or you have a toolkit from a Japanese bike), the cheap looking screwdriver with the removable plastic handle is a JIS.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Codey90]