(Front) brake light problem

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Mar 23, 2015 | 04:29 PM

Dangit

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Joined: Mar 2015

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From: Austin, of course

(Front) brake light problem

There is some slack in my front brake lever which causes my brake light to flicker or at times stay on. If I push the lever forward with my knuckles, the brake light stays off, but if I don't do this, the lever will eventually activate the brake light. It's as if the master cylinder plunger isn't pushing against the lever hard enough and not holding the lever completely open.

Any ideas before I frustrate the heck out of myself trying to diagnose this problem?

Thanks in advance.

Mar 23, 2015 | 08:27 PM

okcjetmech

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Joined: Mar 2008

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From: Oklahoma

Sounds like either you have some gunk in the piston bore preventing the spring from pushing the piston all the way back and or the spring inside the piston bore is corroded and weak or binding in the bore.
you might opt to rebuild it, it easly and not very expensive.

Mar 24, 2015 | 09:00 AM

enodrano

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From: Rochester, NY

So I have this issue with my bike as well. The plunger slides in a rubber sleeve that dries out. When this happens the spring can't return the plunger far enough to disengage the brake light switch. You just need to lubricate the plunger. Do not use penetrating oil like WD-40 though. Use a silicon spray oil or something that is safe on rubber seals. You will eventually have to rebuild when the seal wears out though.

Mar 24, 2015 | 04:08 PM

Dangit

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From: Austin, of course

Thank you both. Now I have some direction.

Mar 26, 2015 | 01:13 PM

grbrown

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From: Bedford UK

I'd strip and inspect your handlebar master cylinder first. When I did that a few years ago I was disgusted at what came out! On many bikes, including mine, the master cylinder points up a little, so the fluid doesn't flush everything out when being bled, hence 'stuff' can accumulate inside. You can get an overhaul kit which replaces all the essential parts inside

Mar 29, 2015 | 07:20 PM

Dangit

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From: Austin, of course

grbrown, While working to fix this, I had actually considered going the extra step to replace my brake fluid. After a period of time/miles, the viscosity and efficacy brakes down.

Since this is a new-to-me scooter, it would probably be good to put in new brake fluid while I'm at it.

rd