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Author Topic: 1978 CB750K Missing on 1&4  (Read 1150 times)

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Offline zeus87

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1978 CB750K Missing on 1&4
« on: August 01, 2008, 09:40:17 AM »
Bike ran mint for a couple of weeks, slowly developed what felt to be cyclinders loading up with fuel...Pull off the side of the road, rev it up a few times and it would be good to go.  Last night was the last of that cure, it is running on 2 cylinders, 1&4 fire very rarely if you hold the throttle at a constant it will chug that spudder as if the cylinders kick in once in a while.  Checked my contacts, all seems well.  Only other thing, I checked my battery after the 1st time this had happend and the breather line got pinched under the seat causing one of the fill plugs to blow out and leak 50% of the acid from three of the chambers.  Anyway, i filled them back up with distilled water and charged it up, is it possible the battery is shot?  it fires the engine instantly.  Also, i have a parts bike 78F but before i switch the coils over, how do i test if they are bad?  what should the read when tested, and how exactly do i test them.  Thanks in advance!!  Good thing my jeep has the interior out to be rhino lined...looks like i will be taking my girlfriends scooter.
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Online Deltarider

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Re: 1978 CB750K Missing on 1&4
« Reply #1 on: August 01, 2008, 09:58:15 AM »
Why don't we read you had a look at the plugs and...
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Offline zeus87

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Re: 1978 CB750K Missing on 1&4
« Reply #2 on: August 01, 2008, 11:01:49 AM »
wet with gas, no sign of firing.........
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Offline zeus87

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Re: 1978 CB750K Missing on 1&4
« Reply #3 on: August 01, 2008, 11:00:28 PM »
no one?
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eldar

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Re: 1978 CB750K Missing on 1&4
« Reply #4 on: August 01, 2008, 11:06:59 PM »
If this is on BOTH 1&4, then it is ignition related, not fuel. If you have another coil, put it on and see what happens. Since you use points, maybe swap the 2 and see if the issue moves to 2&3. If it does, then bad points or condensers.
If no change, swap the coils around and see if the problem moves. I doubt it is the battery as that would affect all 4 plugs.
Most likely points or coil.
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Offline TwoTired

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Re: 1978 CB750K Missing on 1&4
« Reply #5 on: August 02, 2008, 12:01:51 AM »
Got a spare set of spark plugs?

Does the bike have any changes from stock?
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Offline zeus87

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Re: 1978 CB750K Missing on 1&4
« Reply #6 on: August 02, 2008, 07:27:55 PM »
tryed a new battery (after issue, and it tested bad) well anyway negative on that one.  Im going to try swapping coils and or points.  Stock electrical system...Thanks
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Offline GammaFlat

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Re: 1978 CB750K Missing on 1&4
« Reply #7 on: August 02, 2008, 08:19:22 PM »
Quote from: zeus87 on August 02, 2008, 07:27:55 PM
tryed a new battery (after issue, and it tested bad) well anyway negative on that one.  Im going to try swapping coils and or points.  Stock electrical system...Thanks

To get more reliability out of your points, you might want to try the HondaMan ignition.  It works in conjunction with your points.  Your bike won't be as sensitive to the condition of the points and it won't wear them out anymore either.  You can also take the condensor out of the loop (disconnect it).  http://forums.sohc4.net/index.php?topic=31821.0

If you don't want to do that, I have a Dyna-S with a couple hundred miles on it I'll be selling soon.  Do you still have your stock tank and saddle you were selling?  ;)

On the other hand, Eldar might be right about the coils....

When I have issues I don't mind firing the shotgun to kill the problem dead.... I might not learn as much as I would by carefully testing or replacing one part at a time but I hope to get more "up time" with my approach. 

Keep us posted.

« Last Edit: August 03, 2008, 09:11:57 PM by GammaFlat »
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Offline zeus87

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Re: 1978 CB750K Missing on 1&4
« Reply #8 on: August 02, 2008, 11:08:22 PM »
ive got my backpack packed and my shoes tied tight....Pulled the coils and points off my parts bike, off to my girlfriends to see what i can find.  (It would be nice to have my jeep and trailer about now.... seats are being reupholstered)

I'm going to hold off on selling the seat and tank for now...Kind of at a standstill with it all, just enjoying the ride time.  I might move up to alaska in may, so i dont want to buy and sell now having a set decision yet.  Thanks ALL..
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Offline Gregorymoto

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Re: 1978 CB750K Missing on 1&4
« Reply #9 on: August 03, 2008, 08:35:17 AM »
No need to pull the points and coil off to test them, get a voltmeter.
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Yep, i have issues with this sort of stuff.

Offline BobbyR

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Re: 1978 CB750K Missing on 1&4
« Reply #10 on: August 03, 2008, 09:54:13 AM »
A few years ago I had the same intermittent problem. It was the wire that led from the points to the coils. It had chafed and was shorting out. Check those wires while you are at it.
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Offline Johnie

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Re: 1978 CB750K Missing on 1&4
« Reply #11 on: August 03, 2008, 05:46:13 PM »
A friend of mine just had the exact same thing on a 1979 750 Limited.  He went through all the coil stuff since he is electronic ignition.  The problem was the electronic pulse sensor.  Not sure if you have one on yours but thought you would like to know...good luck with it.   
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Offline zeus87

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Re: 1978 CB750K Missing on 1&4
« Reply #12 on: August 03, 2008, 11:22:09 PM »
Bad contact at the points...moved the points/condesor wires on the head side of the little bolt to the nut side and shes running like a champ again.  Thanks everyone!
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