Brake light blowing fuse

C

Coltron

New Member
Hi everyone,
I'm still fairly new here and before you ask i did use the search function first. I recently bought a CB450 that runs and drives and all the good stuff. Didn't realize until i got it home that the brake and taillight were not working. Talked to the guy i bought it from and it turns out when he switched over to a front drum brake he forgot to wire up a brake switch. No big deal, i bought a front brake assembly and switch from a cl350. And this is were i start pulling out my hair.
Turns out the tail light was just a loose connection, so i have a running tail light now. But when i plug in the front brake switch (Brand new still in the package when i bought it) it blows the 15A fuse that the whole bike is wired to. If i hold the plunger on the switch down its fine, but the when i release the plunger the taillight goes out and the fuse blows. I have the switch plugged into the green/yellow and black wires coming from the headlight bucket.
I figured the fuse blowing was due to a bad wire shorting out the system. So i did the light bulb into the fuse holder trick. With the key in the off position the bulb stays off, when i turn the key to the on position but leave the headlight switch off the light turns on. Does this mean there is a short since the bulb in the fuse holder comes on while the headlight and taillight would be off? I went through the wiring and wiggled every wire i could find to see if the bulb would flicker but it gave off a steady glow the entire time. There is a ground wire from the frame to the rear fender under the seat to ground the taillight so it turns on, could that cause a problem? The other thing i was wondering is if i can't figure out the problem, would I be able to wire the front brake switch separately to the taillight assembly to activate the brake light?Also, I haven't tried the rear brake switch plugs yet but i will be doing that Thursday morning. If those work i will just splice some longer wires the the switch and run it from the rear switch plugs as I don't plan on running a rear brake switch.
The taillight is a hooded lucas style tail and has a 12.8v 23/5W bulb in it. I'll post up what pictures i have on my phone and take a few more tomorrow morning to give a visual to this aggravation.

Thanks for any info/help!
 
Brake light blowing fuse

These are the wires I'm plugging the switch into.
 

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Brake light blowing fuse

And because everyone likes to see the bike with the issue in question. Lol
 

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Grab a multimeter and measure the resistance between the black and green/yellow wires in both the harness and the front brake switch.

There should be no continuity in the brake switch unless the lever is depressed. When the lever is depressed, resistance should be very near 0 ohms.

Measuring resistance in the harness, there should be somewhere between 50 and 100 ohms.
 
Brake light blowing fuse

Sonreir said:
Grab a multimeter and measure the resistance between the black and green/yellow wires in both the harness and the front brake switch.

There should be no continuity in the brake switch unless the lever is depressed. When the lever is depressed, resistance should be very near 0 ohms.

Measuring resistance in the harness, there should be somewhere between 50 and 100 ohms.
Click to expand...


I would do that if I owned a multimeter and knew how to use it. Haha
 
Between $10 and $20 and most hardware stores.

It's one of those essential tools when owning an old bike.

Or, if you'd rather, shop time is usually $100/hr or less. ;)
 
Brake light blowing fuse

Found the problem. Had a connection in the tailight that was touching the housing and shorting the system. No more worrying that someone is going to rear end me. Now it's tune up time, because the bike is topping out at around 60mph. It did sit for almost a year though. So hopefully some fresh plugs give it a little more pep
 
Brake light blowing fuse

Got a new issue. When riding around town I can get up to speed fine. But on the highway the bike seems sluggish. Seems a bit slow starting out from a stop. Accelerates decently after it gets going and can hit redline up to 4th gear. When I get into 5th I have to keep the throttle wide open to stay at around 5-6k rpms. GPS clocked me going around 55-60mph. When I get to a upward slope (even a small one) on the highway I have to downshift so I don't start slowing down. The bikes sound gets deeper and more of a boggy sound on the highway at wide open throttle. I'm shifting at around 5-6k in the other gears.
Also just put in new spark plugs gapped to .27 and new fuel lines. Tried to loosen up the brakes a little thinking I over tightened them but doesn't seem any different.
 
You might check the mechanical timing advance mechanism located behind the points to see if it is rusted and not operating correctly. It should turn slightly in one direction and then spring back.
 
I keep finding the problems on my own...this never happens haha. Turns out the left carb is getting fuel, revving up nice but the right carb chokes and bogs out when i try to rev just that carb. Checked the petcock for a block when i replaced the fuel hoses the other day and fuel flows through perfect. So chances are my carb is gummed up from sitting for a while. Going to pull it apart and clean it out to see if that helps. Running on one carb would definitely explain the lack of power.
 
If you think riding a 225 is fun, wait until it's a 450! Seriously, don't ride it until you get the dead cylinder figured out.
A wise man one said "90% of all carburetor problems are electrical".
Make sure your spark on the right side is OK before you tear into the carb. Pull the plug afetr running it a short time and see if it is damp. If so, you're getting fuel.
 
Brake light blowing fuse

Too late, I already pulled and cleaned the carb. Runs exactly the same after I cleaned it though. So it's either electrical or I have a rip in the boot that connects the carb to the engine, causing a vacuum leak. I'm going to check for a leak because when I cover the velocity stack on the right carb the bike continues running the same. Doesn't bog down or stall at all. So im guessing its leaking and getting enough air from the leak to stay running? Also when I remove my palm from the stack it has fuel on it.

Also, I dropped the bike down into the grass, like a dumbass, while trying to push it up a step into my backyard. The weight of the bike falling over caught me off guard haha. It fell on the side with the problematic carb. Might have put enough stress on the old boot to rip it.
 
I think you need to slow down and determine the actual cause. The majority of mechanics is proper diagnosis. You can go on a SWAG (Simple Wild Ass Guess) and spend all summer chasing a problem if you just jump at it without knowing what you are after.
There are lots of ways to "clean" a carb... wiping it off with a shop towel is one. Sounds to me like you knocked this one out in short time. Did you soak it? How about verifying each tiny port is clear with either spray carb cleaner or compressed air? A micro chunk of shit you can hardley see can block a jet tighter than a Nuns puss.
 
Brake light blowing fuse

I did rush into it. Turns out is was an unplugged wire from the right coil. Must of pulled it while tracing the taillight problem. Whoops. Bike runs much better now. Just needs new throttle cable and intake boots to be where I want it.
 
Brake light blowing fuse

So have a new issue. I bought a full engine gasket set from dcc and the gaskets and all that fit fine but the copper crush gaskets are a tad too large to fit in the exhaust ports on the head. Am I supposed to just put the collars and everything together and use the pressure from bolting the headers down to get the gaskets in and seated correctly? Or should they fit in without any issues?
 
Brake light blowing fuse

Good point, just figured I'd keep all the questions in one post rather than clogging up the forums haha.
 
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