Re: 1972 - CB750 Taillight Issue - Request guidance

Posted by tyler on
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1972-CB750-Taillight-Issue-Request-guidance-tp4022629p4022639.html

sgtslag wrote

Tyler, welcome to the forum!  Now, for the nitty-gritty...

Are you certain it takes an #1157, dual filament bulb, in the rear?  A lot of bikes only have signal lights (#1156, single filament bulbs) in the rear, with running lights (dual filament, #1157 bulbs) up front.  Please go back to Clymer, and confirm, or, better yet, pull the bulb out of the rear turn signal assembly, and look inside at the contacts:  are there two contacts in the bottom, or just one?  If there are two contacts, it takes an #1157 bulb (7W running light/23W turn signal filament -- same bulb used in the brake light assembly).

Now, about the voltage reading of 0.29 Volts.  That ain't right!  You have some sort of short circuit going on somewhere.  Trouble shooting electrical is very difficult to explain verbally.  If you have no experience reading a schematic, it is best to either find a YouTube Video to explain it, or find a friend who is knowledgeable in electrical/electronic circuits to assist you.  Most guys can be bought with liquid refreshments.


Now, about that uber-headlight...  The standard automotive headlight is a 55W/60W headlight.  Anything brighter, is illegal in most every state.  If you install a standard, 55W/60W Halogen bulb, you won't have any issues seeing at night, and you will have a high-beam!  "And there was much rejoicing!..."

If necessary, you can use an automotive relay (~$5) to control that uber-headlight, and power it directly from the battery, with an inline fuse to prevent a fire, but this is overkill, IMO.  It can be done, but I would recommend more liquid refreshments offered to your electrically experienced friend, or more YouTube Videos (and more liquid refreshments...).

If you still need more lights, there are LED's that put out 900-1,800 Lumens (standard 55W/60W headlights put out 700 Lumens), which can be purchased, and added to your bike's engine guard bar (assuming you have one installed already), and wired into the battery with a relay (see notes above about liquid refreshments).  These LED's consume around 6W-15W only, per LED, but they cost a bit of change.

Check the light sockets for how many connectors are in the bottom, and get back to us.  Cheers!

Are you certain it takes an #1157...?
Yes, I'm certain.  The old taillight bulb was 1157 and the Clymer book says the same (M341, page 146, table 1). I just took the rear taillight lens apart and confirmed two connectors.  Here is a photo:


As for the headlight the book says stock is 12v 40/50w but does not supply a part or SAE number. I just took apart the headlight assembly and saw "AutoPal 12V 60/55W" written on the bulb. As for staying legal... I'll take it under advisement.

I appreciate the suggestion of adding LED lights or hard-wiring the headlight but I do not want to take the bike that direction.

I'm a novice when it comes to wiring / electrical for bikes so hopefully I can get the job done.

Thanks sgtslag.