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Author Topic: 1 and 4 cylinders cut out  (Read 2280 times)

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Offline Chuck Hahn

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1 and 4 cylinders cut out
« on: February 02, 2018, 12:13:33 PM »
Idles fine with nice blue color seen with my Colortune plug.  But when I run up the RPMs both 1 and 4 go dead and no fuel burn is seen with the colortune.  This kicks in around 3500RPMs.  Let off the throttle and RPMs drop and I get the nice blue flame back.  Just pout two new spark igniter units on it and the timing looks spot on with the timing light.  Very puzzling...so what say you guys???


Think a ground wire from the bolt that holds the spark igniters to the battery box directly to the ground of the battery would help??  Frame ground up by the steering stem is clean and no corrosion.

Bike is a 79 CB750K with a little over 13,000 on the clocks.  I checked the gap at the pulse generator as well by the manuals specs and its at .016 gap
« Last Edit: February 02, 2018, 12:18:19 PM by Chuck Hahn »
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Offline Terry in Australia

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Re: 1 and 4 cylinders cut out
« Reply #1 on: February 02, 2018, 01:52:55 PM »
Well as you've probably learned Chuck, Honda's first electronic ignitions were rubbish. I still remember smelling the ignition on my 1980 CB900F melting in my driveway just before I sold it, thank God. Personally I'd rip that ignition out and replace it with a Dyna 2000, but for $499, it's probably worth more than the bike. Cheers, Terry. ;D

https://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-dyna-high-performance-ignition-kit-cb750-cb900-cb1100-618-861.html
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Offline Don R

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Re: 1 and 4 cylinders cut out
« Reply #2 on: February 02, 2018, 02:05:23 PM »
 Try the ground wire. It's cheap and can't hurt. Could a coil be breaking down? It would be nice to have some known good parts to try.
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Offline Yamahawk

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Re: 1 and 4 cylinders cut out
« Reply #3 on: February 02, 2018, 02:42:40 PM »
Chuck,
  Is the plug wet after a plug chop with the no fuel burn indicated on the Colortune? Check both plugs to see if they are wet, if they are, it could be the one ignitor for 1-4 cylinders. But hey, for $10 each, you might have to go through a couple. New ones are much preferred, but as you know not cheap. Swap the ignitors around and see if you get 2-3 dead. If so, buy another $10 GL1100 ignitor, or send that one back. The fellow said unconditional returns, I believe...

Charlie
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1971 CB750K1 (newest bike), 1996 Royal Enfield 500 Bullet (therapy bike), 1981 Yamaha XV920RH, 2006 Kawasaki Concours (retirement bike), 1975 Yamaha RD350 (race bike), 1989 Honda VTR250 Interceptor (race bike), 1986 Kawasaki EX250 Ninja (race bike in progress), 1985 Honda Elite CH250, 1973 Yamaha GT1 80cc, 1974 Yamaha DT360 project bike.

The Only Thing Necessary for Evil to Triumph, is for Good Men to do Nothing.
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All Things work together for good, for those who love God and are the Called according to His purpose.
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Offline crazypj

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Re: 1 and 4 cylinders cut out
« Reply #4 on: February 02, 2018, 04:11:34 PM »
Stick a couple of early GM ignitors in there, about $10.00 each (US $) Probably find the same  thing on a Holden, just for Terry  ;D
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Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #5 on: February 02, 2018, 05:52:32 PM »
Terry..customers bike not mine.  But this is a first that ive run into with the fire going out and then coming back at low RPMs.  never seen anything like it before.  I will try swapping the plugs at the harness for the igniters and see what happens Charlie.
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Offline crazypj

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Re: 1 and 4 cylinders cut out
« Reply #6 on: February 02, 2018, 06:02:33 PM »
Advance mechanism isn't stuck?
Oh, just remembered something. Does it do same with tank off and running from a fuel bottle?
I worked on a CB900 once that had similar problem, can't remember if it was throttle or clutch cable vibrating and 'pulling' on primary side wiring connector. I was almost tearing my hair out as it was so intermittent when tank was fitted but not when tank was off
« Last Edit: February 02, 2018, 06:07:18 PM by crazypj »
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Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #7 on: February 02, 2018, 07:16:05 PM »
Crazypj..  Gravity bottle feeding it. I put new wires on between coils and wires.  its wierd for sure.
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Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #8 on: February 02, 2018, 07:20:12 PM »
what are early GM igniters???
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Offline Yamahawk

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Re: 1 and 4 cylinders cut out
« Reply #9 on: February 03, 2018, 07:19:39 AM »
« Last Edit: February 03, 2018, 07:22:47 AM by Yamahawk »
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1971 CB750K1 (newest bike), 1996 Royal Enfield 500 Bullet (therapy bike), 1981 Yamaha XV920RH, 2006 Kawasaki Concours (retirement bike), 1975 Yamaha RD350 (race bike), 1989 Honda VTR250 Interceptor (race bike), 1986 Kawasaki EX250 Ninja (race bike in progress), 1985 Honda Elite CH250, 1973 Yamaha GT1 80cc, 1974 Yamaha DT360 project bike.

The Only Thing Necessary for Evil to Triumph, is for Good Men to do Nothing.
Edmund Burke

All Things work together for good, for those who love God and are the Called according to His purpose.
Romans 8:28

Though He slay me, Yet will I trust Him...
Job 13:15
will you trust Him...?

Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #10 on: February 03, 2018, 07:44:48 AM »
What are the odds the pulse generator is going wonky??  I havent read that they are problematic..least that I can find reads on them.  Anyone out there make aftermarket replacements???   I will do the screwdriver from rotor to pulse generator test today as well as try swapping the igniter plugs like Charlie suggested.
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Offline crazypj

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Re: 1 and 4 cylinders cut out
« Reply #11 on: February 03, 2018, 10:58:46 AM »
The cheaper one.  (4pin)
You can get 'pattern' instead of MSD for less than half that price.
The main issue with them is being inside distributor in engine compartment, the heat kills them
Mounted on an alloy plate under seat or side panel they will stay cool enough to be reliable
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Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #12 on: February 04, 2018, 03:12:16 PM »
I swapped the original coils for s set off a 78 KZ50 that i knew were good and it took care of all problems.  sorry to be a pain in the neck but I dont do electrical problems. Had i knew this bike had electrical issues i would never had taken it in to work on.
« Last Edit: February 04, 2018, 03:14:07 PM by Chuck Hahn »
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Offline Terry in Australia

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Re: 1 and 4 cylinders cut out
« Reply #13 on: February 04, 2018, 03:16:59 PM »
Hmmmnnn, I wonder if I could swap my wife for a set of KZ750 coils? ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline Chuck Hahn

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Re: 1 and 4 cylinders cut out
« Reply #14 on: February 04, 2018, 03:18:41 PM »
Send me pics of the wife.  You paying postage??   LOL
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Offline crazypj

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Re: 1 and 4 cylinders cut out
« Reply #15 on: February 10, 2018, 08:59:10 PM »
Quote from: Terry in Australia on February 04, 2018, 03:16:59 PM
Hmmmnnn, I wonder if I could swap my wife for a set of KZ750 coils? ;D

I know the feeling. Wife is more than twice the woman I married
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I fake being smart pretty good
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Offline Terry in Australia

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Re: 1 and 4 cylinders cut out
« Reply #16 on: February 11, 2018, 02:04:34 AM »
Quote from: crazypj on February 10, 2018, 08:59:10 PM
Quote from: Terry in Australia on February 04, 2018, 03:16:59 PM
Hmmmnnn, I wonder if I could swap my wife for a set of KZ750 coils? ;D

I know the feeling. Wife is more than twice the woman I married

Ha ha, we might be related PJ, I think I married her sister! ;D
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I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline crazypj

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Re: 1 and 4 cylinders cut out
« Reply #17 on: February 17, 2018, 05:46:54 PM »
I knew I'd seen a post about GM igniters somewhere on here, found it by accident
http://forums.sohc4.net/index.php/topic,53773.50.html
I was interested in them for Yamaha XS650's a few years ago as I did an 840cc with 277 crank mod.
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I fake being smart pretty good
'you can take my word for it or argue until you find out I'm right'
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