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Author Topic: Main Power Loss  (Read 1480 times)

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Offline SpokeWheels

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Main Power Loss
« on: May 21, 2012, 08:07:30 AM »
Hi All I am new to this site but I am a long time Vintage bike owner. I recently purchased a 1978 Honda CB550K. I am having a problem losing main power however the fuse is not blowing. I have read the "Main Fuse blowing" blog and it was helpful but I was not able to find the real problem. It is an intermittent problem, and I have no idea what may be causing the main power to go out. However when I turn the key switch to the "Park" position I have power to the rear light, so that circuit is not affected. Has any one encountered this problem before? Any help would be appreciated. Thanks.
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bollingball

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Re: Main Power Loss
« Reply #1 on: May 21, 2012, 09:36:17 AM »
Take out the fuse then get to cleaning the fuse holder a 22 cal cleaning brush works good . the fuse should snap in hard enough that you have a hard time pulling it out with your fingers so make sure it is clean and tight. Also look at the rear of the fuse block to see if it has started to melt.

Ken
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Offline SpokeWheels

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Re: Main Power Loss
« Reply #2 on: May 21, 2012, 01:58:14 PM »
Ya Ken I did all that, cleaned the tines so they shine and the fuses fit nice and tight and the power is getting through to the opposite end of the fuse well enough. Even when the power cuts out the power is still at both ends of the fuse. Yes there is evidence of melting on both sides of the fuse box. Maybe I need to replace the main lead to and from the fuse box along with a blade style fuse box? That is easy enough to do I am just wondering if there may be a problem deeper in the wiring that may cause these symptoms? Thanks for your advice.
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Offline LesterPiglet

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Re: Main Power Loss
« Reply #3 on: May 21, 2012, 02:15:00 PM »
I had a problem where the ignition switch contacts would disconnect due to the switch being worn. It wasn't fun riding on a bumpy road. I took it apart, cleaned and tightened it up and it's fine now.
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Offline OneWheelDrive

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Re: Main Power Loss
« Reply #4 on: May 21, 2012, 02:21:44 PM »
Quote from: LesterPiglet on May 21, 2012, 02:15:00 PM
I had a problem where the ignition switch contacts would disconnect due to the switch being worn. It wasn't fun riding on a bumpy road. I took it apart, cleaned and tightened it up and it's fine now.

+1 
I've had problems with the ignition switch internals as well.  Replaced the switch and solved the problem.
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline flybox1

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Re: Main Power Loss
« Reply #5 on: May 21, 2012, 02:35:58 PM »
why replace the ignition switch, it can be easily cleaned? :o
can you replicate the power loss with the bike on stand?
my first thought would be that it might come and go with your bike on center stand, while rotating your bars from side to side.
there might be a loose wire in the headlight can, or at your ignition switch.
also check for wire bundles showing through the factory shrink tubing.  it can get brittle and break at a bend, causing recurring wear of those wires just at that bend..
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

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Offline OneWheelDrive

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Re: Main Power Loss
« Reply #6 on: May 21, 2012, 03:02:03 PM »
Quote from: flybox1 on May 21, 2012, 02:35:58 PM
why replace the ignition switch, it can be easily cleaned? :o

I re-keyed the seat, gas lock, and ignition from another parts bike.
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1975 CB550 cafe
1971 CB500 stocker
2008 Ducati Hypermotard 1100S *sold*
1973 CB350F *sold*
1975 CB550K Project "Keeper" *sold*
2010 Ducati Monster S4RS *sold*
1976 CB360T *sold*
1974 CB550K *sold*
1973 CB750K *sold*
1978 CB550K *sold*
2007 Vespa LX150 *sold*

Offline SpokeWheels

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Re: Main Power Loss
« Reply #7 on: May 22, 2012, 02:06:34 PM »
Thanks to all who responded I will try some of the things you suggested... Let you know what happens in a week or 2  when I get a chance to work on it. Thanks again.
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