Master Cyl screws froze - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 5 (permalink) Old 07-14-2007, 12:04 AM Thread Starter
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Master Cyl screws froze

I recently bought a 1986 vn750. I have tried to open the cover of the master cylinder to put fluid in it as the bubble appears empty but I cant get the screws to budge. They are already partly stripped from somone else trying to get them out.


I dont have the tools to tap them out, and I do want to replace the part altogether but later on. For now I'd like to just add a little fluid to it. Would make me feel better about reaching for my handbrake. I've put a bit of WD40 on it, to sit overnight but I dont expect any change in the morniging because they are really frozen in there and the WD40 cant penitrate in to contact the threads. (I think)

Guess I may have to buy a tapping kit and replace the screws.
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post #2 of 5 (permalink) Old 07-14-2007, 06:20 PM
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Use an Impact driver and hit it softly ......that's what worked on mine
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post #3 of 5 (permalink) Old 07-14-2007, 07:16 PM Thread Starter
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I bought a screw extractor from the hardware store. My nieghbor let me borrow his drill, and came over to help me. I think he wanted to make sure I didnt hurt his drill. Well I think he ran it in the wrong direction and the bit only suceeded to strip the screw ALL the way out. Completely smooth and beveled. So we got a regular bit that was big enough to cover the whole screwhead. We drilled out the head, and a portion of the cover untill it was deep enough that I could pop the lid off over what remained of the screwhead. Then I used vice grips to screw out the remains of the screws.

To my relief there was indeed SOME brake fluid still in there. I took the cover to hardware store along with what was left of the screw threads. Found a match, 5mm x 10 mm (L) and decided to go just a bit longer 5mm x 16 mm (fine threads) along with a couple washers to cover the partial hole we made drilling out the screwheads. Also I went with hexhead screws so I can get them back out with a socket wrench this time.

I cleaned evrything up real good, added some DOT 3 fluid and put it all back together. It isnt pretty with those bolt heads sticking up and the washers and all being visible but I plan on replacing all of the controls and mounts later anyway. It'll do for now so I can at least keep and eye on the brake fluid.

Dont panic if you dont see any fluid in the bubble. My handlebars are rotated back a bit and my levers are up a bit, so the master cylinder is not level, and fluid doest really show in the bubble anyway.

I never did figure out why the screws were stuck so firmly and I dont understand why the fittings in the screwheads were so soft.
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post #4 of 5 (permalink) Old 07-14-2007, 07:47 PM
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My guess would be steel screws in an aluminium housing. Dissimilar metal set up a corrosion cell and freeze the bolts. Apply antiseize compund to the screws. Also check out corrosionx a super migrating lubricant. It beat all others in a migration test. Corrosionx makes WD look like water when it comes to penetration. They also sell a product called rejex that is great

Dennis Huff
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post #5 of 5 (permalink) Old 07-14-2007, 07:58 PM
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Try any and all of the above, particularly the impact driver. Also, try PB Blaster - it's magic compared to any other product I've used. Hit the screws, let 'em sit a day or so, pop 'em with the impact driver, and see if you got 'em.

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