Hello. I'm a new rider who recently purchased a ten year old bike. I have ZERO mechanical know how, but decided that I wanted to learn.
So far I managed to take both the front and rear wheels off to get the tires changed and I managed to change the oil. Since I am unskilled, it took a LOT of fumbling through these to get things going...including breaking some nuts (rear axle nut was stuck and I originally only had a 12 point socket) and bolts (overtorqued an oil filter cover bolt despite using a torque wrench) and buying replacement ones.
Since the bike is 10 years old, I know that all of the fluids need to be changed. I feel comfortable attempting the actual change for the brake fluid from my research EXCEPT I don't want to irreparably damage this area. The front brake works fine, but the sight glass is totally clouded and opaque, so I cannot visually check the condition or level of the fluid.
These are JIS screws and I have purchased replacement screws. Any advice here? Please consider my novice skill level lol.
I bought some screw extractor bits but do not have an impact driver. I have some JIS screwdrivers, a hammer, a regular drill, penetrating oil, and replacement JIS screws.
Thanks!
TL;DR: Just drill these out.
Don't waste your time with screw extractors, new screwdrivers, torches, or any of that.
This always happens with these Japanese style master cylinder covers. The reservoir body and cap are aluminum and the screws are plain steel. You can do the math there easily; you wind up with galvanic corrosion due to the dissimilar metals and they seize.
I don't know how many dozen of these I've had to do over the years. Maybe hundreds. Grab a drill bit just a touch larger than the shanks of the screws (which are typically 4mm) and just drill down right in the center of the screw head. Then the head of the screw will pop off. Stop there.
Once both screw heads are drilled off the cap will come off easily. Then you can unscrew the left over stumps of the screws (conveniently sticking out, thanks to the thickness of the cap) with your fingers. The screw head binding against the surface is what keeps tension on the threads. One the head is drilled off the threaded stumps will just be loose. Fortunately in this case, the reservoir cap is sealed (or ought to be...) and thus moisture can't get in to rust the threads; only the head.
Don't replace these with OEM screws. I mean, you can temporarily since you already have them and you're going to have to use something. But trust me on this, replace them with stainless steel metric M4x0.7 screws, 12 to 14mm length is usually about right, preferably with Allen heads. That way when you have to get in there next season you won't have to go through this whole song and dance again. With both screw heads drilled off the cap should come off easily. Teh
And go slow while doing this, you can't undrill a hole.
And you need the shanks to stick out of their holes to grab onto them.
I've had luck using the impact driver, but you really gotta have the feel of it to know how much force to use and whether it's going work (and not breaking the master cylinder.
But yea, it's a shit combo of aluminum and shit steel screws.