Category Archives: 650

Replacing the Sight Glass

It’s common for the brake and clutch master cylinder sight glasses on Hondas of this era to deteriorate, become opaque, and even crumble and leak. Mine are no exception so I’ve replaced them with mineral glass watch crystals.

Old Sight Glass
Old sight glass. Opaque and weakening.

Once the original sight glass looks like this it is very weak. You can put your thumbnail through it or a piece of gravel at freeway speeds can cause a leak. If you lose your brake or clutch while riding you’re going to have a bad time.
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Brake Switch

Dirty brake switch
Dirty brake switch

Well my brake switch was broken. The rear brake pedal would activate the brake light but the front brake lever wouldn’t. I checked on the brake light switch and found it wasn’t working and was quite warm. With some patience and a couple of small flat head screwdrivers along the seam I was able to open the switch. It’s fairly simple as far as switches go, it’s normally closed and with the brake lever in its normal position it depresses the plunger which opens the contacts and breaks the circuit. When you pull in the brake lever it releases the plunger which brings the two contacts together and completes the circuit. In my case the contacts (red arrow above) were dirty and adding resistance to the circuit.
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