'71 cb450 won't start

C

CThor

Been Around the Block
Hey looking for a little help. When I turn the key on the tail light turns on for a second and then goes off. Nothing else seems to work such as any gauge lights coming on or the start button does nothing. This is my first attemp at building a motorcycle and not really sure what to check to see why nothing is working. I've checked the battery, the inline fuse on the harness and the ground is hooked up. I have a mulitmeter to check connections with just not sure what to check.
Thanks in advance for any help.

Corey
 
Not sure anyone can really help you with this one. It is weird that the taillight comes on for a second. Try jumping it from a non-running car to see if its the battery. Check the ignition switch.

I spent 2 hours the other night figuring out why my front turn signals lit up when I pulled the brake lever. Turned out to be a loose connection on a ground wire in the rear fender running to the taillight. WTF!

Good luck!
 
I just put a new igntion on it today actually. The previous owner has lost the keys and had a friend remove the pins in the lock. I'll just have to go through the whole electrical system I guess. Just wasn't sure where to start.
 
First go to harbor frieght or sears and buy a digital multimeter with continuity , get a quality wiring diagram, open head light shell, remove tank and seat, and start chekcing every plug and circuit for power and continuity, clean every connector you can find with circuit cleaner and sandpaper and check all the grounds. Could be something as simple as a crapped igition switch. Is the battery fully charged? Keep working through everything untill you find the problem, take your time and all will be fine. remember engines need air, fuel and spark. I just went through a '72 Yamaha XS650 and it took me a month to find the problems!!! What a pain in the ass!!! Check the coils for resistance or just change them as a matter of course, 40 year old coils should be considered dead. It's one of the first things I change on an old bike.

Terry
J'ville, Fl.
 
Ok thanks for the response. I opened the headlight, have the tank and seat off. I just put a new ignition on it today. I was wondering if I should put new coils and all that on. I think I'll prob do that since it has been sitting for quite some time and it can't hurt to have new. I'll just have to start going through it all tomorrow when I get some more time than I had today.
 
Okay Thor, put on your patience hat. :) Electrical troubleshooting takes methodical divide and conquer techniques.... First things first. Did you get to start the bike before you put the new ignition in? If yes, then your ignition installation is suspect. Check each connection you made, recheck it, and then make sure it has been terminated solidly and properly. Twisting wires together and covering with tape is not proper. Check you CB 450 wiring diagram to make sure your wires all go to where they are supposed to. Reseat ALL connections. Who knows what might have vibrated loose while bringing home your new baby. If your taillight comes on, then quickly goes off, that indicates a faulty connection, or a grounded connection that shouldn't be. Check your battery with your multimeter set on DC voltage, and the key OFF. It should read over 12 VDC if properly charged. Turn the key, and it should drop some, not totally sure how much, but not more than 2vdc, if memory serves. If lower, you need to charge your battery.

You have a regulator, and a stator and an ignitor on the old cb's right? All of these can be easily checked with your multimeter, and the right honda data for their proper readings. I'm a Suzuki guy, so someone else will have to tell you that stuff.

You can check your coils for spark by pulling a plug, and setting it so the electrode, the business end, is touching the block. You should see a bluish looking spark as you hit the ignition switch. You won't get accurate tests here until you sort out your starting issue. My guess is that your coils are not the problem. I'm leaning towards battery needing charged. Did the bike run when you got it? Is it sitting in the cold? Batteries can easily go flat in the cold....

Tools.... Digital multimeter, under 20 bucks, Harbor Freight. Battery Tender, under 30 bucks, Walmart. (I got the Black and Decker for 20.)

Do one test at a time, and then put things back to the way they were. Don't change your setup until you find a fault. I replaced my regulator last year, after a week's worth of ignoring a shotty connection made by the previous owner. Leave no stone unturned.... Good Luck, and Happy Hunting.

loudest143
 
The bike did not run when I got it. I didn't get anything with the old ignition either. I just got the new one so I would have keys for the bike. The bike is sitting in the cold but I have been charging the battery to make sure it doesn't freeze. I get the same reading with the key on and off. 12.7 volts. Hooking the new ignition up was just unplug one and plug the new one in. So shouldn't be any connection issue there.
 
Okay, so the key/ignition is plug n play. I'll assume it was a new part, so no problems there. Battery tests out fine! I would check your ignition switch next and it's wires. When you push the ignition switch, it does nothing, making no mechanical noises at all? It's entirely possible that the ignition switch is not functioning properly. Hey, it's pretty old stuff, right? :) I'm gonna guess that someone on here has bypassed the starter switch in some fashion, and can point out how to do that safely. Unfortunately, I don't have wiring diagrams for hondas, so I can't really advise you on which wires to touch together, or where they might be.... If your bike makes no mechanical or electrical noises when you hit the ignition switch, then there are a couple of things you can rule out for the moment. Coils, sparkplug wires and spark plugs. I am NOT saying they are fine, but it sounds like your bike isn't even getting that far yet.

Things to check out: Ignition switch wiring, and its' mechanical functionality, and starter motor and starter wiring. If the starter isn't making its starter noises, it could be faulty or the wiring to it may be an issue. If you can start it with the kickstart, this might help with figuring out that starter motor is an issue at least. Ignition switch comes before all that, so that's where I would start since you have what appears to be a good working battery. Keep on chargin' that beast.

Couple of questions.... Do you have new plugs? Are the spark plug wires well connected to the coil and the plugs and free of cuts and nicks? Not such a big deal right now, as we're just trying to get the ignition to work, but it can be important as you try and KEEP her runnin'.

I hope this helps.

loudest143
 
Well I pulled all the wires out from the head light and pulled the starter switch apart and that seems to be ok inside. It just seems like nothing is getting power from the battery. Shouldn't the gauges light up when the key is on? Nothing seems to happen with the key on. Right now I have all the wires unhooked except the ones that go to the right hand control.
 
CThor said:
Well I pulled all the wires out from the head light and pulled the starter switch apart and that seems to be ok inside. It just seems like nothing is getting power from the battery. Shouldn't the gauges light up when the key is on? Nothing seems to happen with the key on. Right now I have all the wires unhooked except the ones that go to the right hand control.
Click to expand...

stupid question but are you only turning the key to the first position on the ignition ? if so than the neutral light should come on if you are in neutral and the bike should be getting power, i have a 1972 cb450, when i turn the key to the second position, i get no neutral light

have you pulled the plugs and kicked the bike over whilst the ignition was on to see if the plugs are getting spark ?
 
So at first, you were getting the taillight to light for a second when you turned the key, and now you've got no taillight coming on at all, is that correct? It appears that when you turn the key to the first notch you should have the neutral light come on, and I've got to assume your headlight and taillight should come on at the same time in that first position. On my bike I can turn to the first position and get headlight, taillight, neutral lights, and I can even operate the signals.

And you cannot do any of that.... Hmmm... We really need a wiring schematic. I am going to offer up one thing here, and it's only based on a problem that I had on my bike. Keep in mind that I have an eighties Suzuki, so we are comparing apples and oranges.... I had a ground wire that was not attached to the frame coming directly from the battery. Now I've got OTHER ground wires touching the frame, and this one seemed to be vital to my system operating correctly. Long story short, check your ground connections at the battery, and then also check where they attach to either the motor, or to the frame. Check to make sure you have clean metal where they attach to the ground source. You can take a bit of sand paper to clean up any corrosion or rust that might be preventing you from getting a good ground.

Let's be honest here. You need a positve and a negative wire and a complete circuit to make your lights come on. Since your headlight doesn't come on, is the bulb good? You can test it with your meter, but I bet you've already done that.

Dumb question, do you have fuses on the bike, and if so, have you checked them with your meter? Also, does the fuse box have good connectivity at the fuses? Meaning are they free of corrosion and rust? Mine are behind my left side cover. Sheesh, sorry I didn't think of this sooner. I imagine you've been through all of this.

Autoguy brought up the kickstarting idea. Have you attempted this yet? It might be nice to know if the sparks are getting power.

Hey Honda owners out there! Is there any way the ignitor could be causing issues? On my Suzi it doesn't prevent the electrics from working.

Hang in there Thor. You'll get there. ;D
 
Well got some good news. I cleaned up the ground on the frame. Now the tail light stays on with the key and the headlight will turn on. That was with the key in the first position past off. The wires were not getting spark though. Is it suppose to? Or does the key have to be in the 2nd position past off for starting the bike? I'm thinking that the starter button issue is that the metal inside the switch wasn't getting grounded when the button was pushed in. I had to press it up against the bars pretty hard to get it to work. Now I go back out there and it won't do anything again! I'm going to go get some new allen head bolts to put the switch back on the bar properly and try again.
 
Just keep working through it and eventually, all the bugs will get worked out.

I believe the switch only has 3 positions: Off, On, and Park. In Park, only the taillight is supposed to be on. Not really sure what that is for. By wires not getting spark, do you mean the spark pugs? If so, the engine has to be turning over to get a spark, and the key has to be in the On position. The kill switch also has to be in the Run position.

The starter button is fairly simple. The yellow/red wire coming from the selenoid up to the handlebars just has to be grounded for the starter to turn. The bars are grounded, thus the control housing is grounded. A metal bracket is mounted to the housing which positions the button and provides a place for the spring to push against. Therefore the little metal rod on the button is grounded. When you push the button, the little metal rod goes through the bracket and touches a contact pad on the end of the starter wire, completing the circuit. The bracket was missing in my housing and I had to make a new one out of some aluminum sheet. Make sure your bars are grounded, then the houseing, then the bracket.... This is of course, if you have stock controls.
 
I think that was my problem was the button wasn't getting grounded. Now I got that fixed and it will turn over with the starter. I don't think I'm getting spark though at the plugs. I pulled a wire and tried to get it to arc while turning over but got nothing. I'm starting to think my battery has gone bad though as well. My charger says it is full but it doesn't power up the bike for very long and after one start attempt it won't go again. I'll have to pick up a new one and give everything a try after that. Would a low battery cause the plugs not to get any spark? As long as the motor was turning it should be generating spark correct?
 
I think so. Coils hooked up right? Fresh plugs gapped correctly? Good question to ask over at hondatwins.net. Those guys know their shit. Bill saved me from tearing my engine apart when it got stuck in 5th gear. I do know these bikes will do some odd stuff if the battery is not working properly.

Didn't you say the kill switch was hosed? That could be the problem. You will get no spark if it is not working correctly. I don't have my wiring diagram here but I think the kill switch completes the circuit for the coils because everything will work when it is off, but the plugs won't fire.
 
If you take your battery to autozone or wherever, they should be able to tell you if it's good or not. Are the fluid resevoirs full? When I first got my bike, I borrowed my brother-in-laws battery tender to charge my battery. I charged for a few hours then it said it was full. I disconnected it, then reconnected. It charged for a few more hours then said it was full. I did this a couple time before it actually was full. Also, if your are just trying to get it to run, you can jump it off of a car battery. Just make sure the car isn't running.
 
Ok i'll have to check out the kill switch to make sure thats working properly then. The battery was an extra scooter battery I had in the garage that I think may have frozen before I was able to get a battery tender on it. I can put my charger on it now and turn the key and the neutral light will come one, but without the charger hooked up I get nothing. So a new battery will be my first thing. I'll have to get some help to see if it gets spark while I kick it over. I tried to check myself but didn't have much luck. :D

Thanks so far for everyones help! Its much appreciated.
 
Yay! Progress! Glad to hear you've got a couple of details sorted. Your symtoms with the battery dying after one start attempt does seem to indicate a bad battery. :-\ When you get a new battery, keep it on that trickle charger every night as your working through your electrical issues.

Flugtechnik mentioned a couple of important issues. Coil strength, and fresh, properly gapped plugs. I had a fouled set that had me chasing my tail for a while that LOOKED fine, cleaned up easily and got regapped. They were still fouled, and it was just too hard to tell. You might try buying a fresh set of plugs. Less than ten bucks for another piece of the puzzle that YOU KNOW will be right at least during this process. Peace of mind is worth ten bucks, IMHO. If you want, you could even buy a cheapie set of autolites, just to get you through the testing procedure. NGK otherwise. (at least for me.)

As for the coils, you'll need to get the proper readings for your meter to do the ohm tests. I wish I had that data for you. Once the new battery is charged and in place, I bet you'll be up and running in no time. :D

Post pix of this beast when ya can!

loudest143
 
I have a pic or two in the big arse projects section. I don't really have much done yet. Just removed a few parts and I'm waiting on my seat to arrive. Just wanted to see if I could get it running before I went through all the other stuff. Its been so cold though here to work out in the garage. I suppose I could go fill my propane tank for me heater.... ha ha I was hoping to get by with this battery until my seat comes so I can see what size will fit under the hump. With any luck that will be here in the next day or two. Getting a new set of plugs was already in my plan. It prob wouldn't hurt to get a new set of points and a condensor too don't ya think? They aren't too expensive either.
 
I was looking at this battery. Should be plenty small to fit under the seat hump. Anyone know if its got enough juice for the starter?

http://www.gotbatteries.com/items.asp?params=batteries/SLA/1/Powersonic/PSH-1255/PSH-1255F2/SL118/35L118S5
 
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