Bonneville Front Brake Reservoir Issue

@GoldenDawn Yes funny old one. I have in the past just cleaned out the screw heads and flattened out the edges of the damaged one then tighten rather than loosen a few times tight and loose to get it free. Hoping it all goes well for you.

 

They look (to my untrained eye) very much like JIS so do NOT use or try to use Philips or Pozi drivers. There's a fair chance that the correct size JIS driver will actually work if you're lucky ..... and patient!

https://www.amazon.co.uk/US-PRO-Jap...xt&ref_=fplfs&psc=1&smid=A3P5ROKL5A1OLE&gQT=1


If not, then you're looking at very careful application of an 'easy out' e.g.

https://www.amazon.co.uk/Deals】OriGlam-Extractor-Broken-Damaged-Remover/dp/B06X96FVWX?dib=eyJ2IjoiMSJ9.vTw8XJNiE4I9-bV4uNuQiWRtjCMkc7bxat5mBzsf9vIXR-Ysw7UOgMYJxFnRT3a77K7rKqhhNK1XilacrkmMY1vkUPh2ZBpJK9F5PuJyUnrmMz9eVT3NB9M3DnTRnxd9SXZbS9p3jBFMn8vKjZQKS1yabSPnvGY9QvRBp4KPkC7das3tfPqO-LPiw-SxQuOJH7jPgsowMnPS1cGdSUUc1n66E76HfGWBnq7wgSHZWPUYNjg4w8nz_Dy3xzvZA7Gz-QTcL2fw5HbPuZAhXjq14IP-rRsfgFxGWPoM5wA5dl4.TvnRSaGxcinRuiJkIpi3gY_bbEbAPTqYLS3jTy4eh6k&dib_tag=se&keywords=easy+out+extractor&qid=1743688312&sr=8-9

which is far from ideal in this application.

Can only wish you luck!!

 

Good advice from @Adie P The only thing i worry about is the easy out. Not much to go on there and the starter drill will always drift towards the softer metal unless you have a pilot drill set up. The drivers i think are great and so much so i have just ordered some just in case.

 

I would remove the reservoir and clamp it securely in a bench vice (suitably padded to prevent damage), then very carefully drill a pilot hole, say 2mm in the centre of the screw to a depth of the countersink, then increase the size of the drill by small increments until you have a hole slightly less than the screw shank diameter, then using a parallel punch carefully prise off the screw head and lift off the reservoir lid. You will then be left with two screw shanks which can be unscrewed using grips, or cut a slot in the shank and use a flat bladed screwdriver to unscrew the shank.
I would not work on the job when in place on the handlebars, also be careful not to allow ingress of swarf into the reservoir. Exy outs would be a heavy solution for this delicate job.

 

These are indeed JIS screws indicated by the small dimple on the top. If using the correct screwdriver doesn't shift them, then get a very sharp punch or awl and tap them off by firstly punching a small dimple close to the edge of the screw then tapping anti-clockwise. If you need replacement SS allen screws PM me.

 

Learned quickly from repairing my Lionel cars and locomotives that Japanese Industrial Standards philips head screwdrivers are a must (mine were made in Germany, go figure).

Also, some time ago, learned that brake fluid is corrosive to paint; don't know if modern fluid still is.