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Offline joerizzo0

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HELP!
« on: July 23, 2010, 07:04:17 PM »
i have a 74 cb400f..
will run for a while then seems to have charging issues and dies.. wont even kick start until i charge the battery..

anything i should look for in particular?

its a good night for a ride and im sweating in the driveway!
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1976 cb400f

Offline OldSchool_IsCool

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Re: HELP!
« Reply #1 on: July 23, 2010, 07:08:03 PM »
Grab a volt meter and measure the voltage AT THE BATTERY under the following conditions:

- key off
- bike idling at 1000 RPM
- 2000 RPM
- 4000 RPM
- 5000 RPM

Report back here.
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Offline joerizzo0

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Re: HELP!
« Reply #2 on: July 23, 2010, 07:14:43 PM »
i dont have access to a volt meter at the moment..

may be completely unrelated but the only thing i have done since it ran last was take the rear fender and tail light off to clean some rusty dirt goodness off.... maybe i have a short somewhere...

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Offline Frostyboy

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Re: HELP!
« Reply #3 on: July 23, 2010, 07:20:43 PM »
Quote from: joerizzo0 on July 23, 2010, 07:14:43 PM
maybe i have a short somewhere...
Not really, short circuit = blown fuse & something not working.
You're going to need both volt meter & ohm meter to check charging system.
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Offline my78k

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Re: HELP!
« Reply #4 on: July 23, 2010, 07:23:26 PM »
doesn't sound like a short. I agree with the first step of looking at the charging voltage.

Dennis
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Offline OldSchool_IsCool

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Re: HELP!
« Reply #5 on: July 23, 2010, 07:23:42 PM »
A short in the lighting circuits would pop a fuse.  That would be a separate issue as the charging system isn't fused.  

I suspect you have a loose connection between the alternator, rectifier, regulator or battery.  Check all the big, multi-pin connectors under your side panels.  If all is tight, then there is prolly a failure of one or more of those components.  Did you ever try to jump the bike and accidentally got the jumper cable reversed?
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Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline GammaFlat

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Re: HELP!
« Reply #6 on: July 23, 2010, 07:25:12 PM »
Go to Harbor Freight and get a meter.  If you're lucky, these go on sale for as little as 3 bucks but the regular price seems to be 10. 

http://www.harborfreight.com/7-function-digital-multimeter-90899.html
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Offline joerizzo0

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Re: HELP!
« Reply #7 on: July 23, 2010, 07:32:16 PM »
ill have to dig into it in the morning...
ill post my findings when i find them..

looks like ill just ride the bicycle around the block....
haha

after working outside in the heat today i really wanted to feel the wind in my face...

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1976 cb400f

Offline joerizzo0

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Re: HELP!
« Reply #8 on: July 23, 2010, 08:07:17 PM »
went down to the garage and it fired right up.. took it around the block and everything seemed fine.. weird.  hope that doesnt happen when im out on the road somewhere.
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Offline cameron

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Re: HELP!
« Reply #9 on: July 23, 2010, 08:12:22 PM »
Get a meter. Ride straight to radio shack or something.

Also, don't listen to these jokers regarding a 'short'. :) God knows if you even have fuses.

I have certainly ridden on a mis-wired turn signal, which didn't blow any fuse, and worked fine.. but destroyed my alternator and stranded me in the middle of nowhere. Not all shorts blow fuses. Some light fires. Check out your tail light.. make sure its right.

And get a meter.
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Offline my78k

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Re: HELP!
« Reply #10 on: July 23, 2010, 08:46:11 PM »
my point about the short wasn't that it would or wouldn't blow a fuse but rather that it doesn't tend to drain a battery as was his description. I would buy the short if it was intermittent but he made it sound like it drains the battery (these do that at under 3000 rpm or so) and after charging it was fine....

Dennis
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Offline buttcan

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Re: HELP!
« Reply #11 on: July 23, 2010, 09:31:08 PM »
I'm not sure if this applies to your bike however. . .   My750 won't run for long at idle on just the battery. This is in part due to having a Dyna ignition instead of points however there has to be electricity to run the coil and if you are not recharging your battery properly off the stator then the battery drains until there is not enough juice to run the coils and points.

You need to check that you are charging.
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Offline cameron

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Re: HELP!
« Reply #12 on: July 25, 2010, 02:27:56 PM »
Quote from: my78k on July 23, 2010, 08:46:11 PM
my point about the short wasn't that it would or wouldn't blow a fuse but rather that it doesn't tend to drain a battery as was his description. I would buy the short if it was intermittent but he made it sound like it drains the battery (these do that at under 3000 rpm or so) and after charging it was fine....

Dennis

Totally agreed.
Charging system is #1 suspect.

Still should confirm he didn't pinch anything while toying with that rear light.

(and I don't really think you are a joker :))
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Offline joerizzo0

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Re: HELP!
« Reply #13 on: July 25, 2010, 06:02:49 PM »
I rode the bike about 50 miles down and around the motor speedway last night and it ran great..

My friend has a 2006 repsol 1000rr and he was getting a little upset that more people were talking to me about my bike than his.. haha!

charging system seemed to be working pretty well.. no issues at all.

hopefully it was just a matter of not riding it for a while and nothing more serious.

on to the next problem! need to sync the carbs.. there are a ton of threads on here about that so i might try it myself and then bribe one of my friends with beer if i cant

get it..
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1976 cb400f

Offline Spanner 1

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Re: HELP!
« Reply #14 on: July 25, 2010, 07:15:57 PM »
The problem is not resolved IMO... still need to go thru' the charging system with a meter, or get stranded somewhere, these things dont fix themselves !!, but your young and can push your bike a long way :)
« Last Edit: July 25, 2010, 07:23:11 PM by Spanner 1 »
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Offline cameron

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Re: HELP!
« Reply #15 on: July 25, 2010, 11:19:46 PM »
Not having a multimeter is like not having a screwdriver :)

Whatever loose wire you had probably bounced back where it is supposed to be... so you are good for a while.
Until you bounce it back off.
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Offline 77cafe750

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Re: HELP!
« Reply #16 on: July 26, 2010, 12:32:32 AM »
i tend to concur with cameron get a volt meter and perform the old wiggle and jugle test while checking bat voltage at various rpm
just my two cents crash
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Offline joerizzo0

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Re: HELP!
« Reply #17 on: July 26, 2010, 03:52:14 PM »
Yeah im gonna spend some time going through and cleaning and checking connections sometime soon.. this bike sat for a long time and quite honestly its got some wiring issues.. my turn signals and gauges are all messed up.. i have the wiring diagram but its more of a trial and error game..

also need a new seat, would like some new bars, need to paint the tank, sync the carbs.... its a laundry list.. but im not complaining.. its fun!
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