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Author Topic: Running on one cylinder intermittently (CB450)  (Read 837 times)

Offline redrover

  • Posts: 193
Running on one cylinder intermittently (CB450)
« on: Jun 04, 2018, 15:26:55 »
Brought this CB450 back from the dead.

Valves adjusted
Fresh oil
Rebuilt the carbs
Reg/rec installed
LED H4 headlight (to draw less power from the system)
Pamco Ignition (had it running on points first)

The left cylinder header wasn’t getting hot at all... After tinkering with the carbs for days and days, finally fired on both cylinders, but when I ride it... The cylinder will start/stop even under throttle load, the cylinder will die and then kick back in intermittently.

Do I take the carb apart AGAIN (possibly tenth time)? What else can I try?




Offline redrover

  • Posts: 193
Re: Running on one cylinder intermittently (CB450)
« Reply #1 on: Jun 04, 2018, 15:28:17 »
Btw... compression test results:

Right cylinder 179psi
Left cylinder 174psi

Anyone any thoughts?

Offline TheCoffeeGuy

  • Posts: 644
  • Books, Books, Books, knowledge is within
    • The Coffee Guy's Blog
Re: Running on one cylinder intermittently (CB450)
« Reply #2 on: Jun 05, 2018, 09:21:59 »
Sounds more like a loose wire.  Start with the high tension wires making new connections on both ends.   The wires themselves could be leaking or the caps could be old and they will convey electricity and ground out on the head.  Check the resistance and continuity on the plugs as well.  Then  check the low side wires all the way back for shorts and loose conexions all the way back to the spark generator.
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike
1982 Honda CB650 Chopper light

Offline redrover

  • Posts: 193
Re: Running on one cylinder intermittently (CB450)
« Reply #3 on: Jun 05, 2018, 22:54:50 »
High tension wires?

Offline themotoworks

  • Posts: 97
    • the motoworks
Re: Running on one cylinder intermittently (CB450)
« Reply #4 on: Jun 06, 2018, 07:58:54 »
how old is your battery? 

Offline sebwiers

  • Posts: 35
Re: Running on one cylinder intermittently (CB450)
« Reply #5 on: Jun 06, 2018, 12:11:54 »
High tension wires?

I'm assuming he means the ones that run from the coil to the spark - IE, high VOLTAGE.  If you bike has just one coil it is running wasted spark and the problem is almost certainly a bad connection from coil to spark plug.  If it has 2 coils then it may be that one of the coils is sometimes not charging / discharging as it should.  That's probably a bad connection to the coil, or maybe the coil itself is bad.

And yeah, in my experience, intermittent issues are usually electric.  This does not sound like a fuel / valve / timing issue, especially as you say you just worked on those things.

Offline redrover

  • Posts: 193
Re: Running on one cylinder intermittently (CB450)
« Reply #6 on: Jun 06, 2018, 16:21:10 »
how old is your battery?

Battery is new, oem. Cranks right up over and over.

Offline redrover

  • Posts: 193
Re: Running on one cylinder intermittently (CB450)
« Reply #7 on: Jun 06, 2018, 16:30:26 »
I'm assuming he means the ones that run from the coil to the spark - IE, high VOLTAGE.  If you bike has just one coil it is running wasted spark and the problem is almost certainly a bad connection from coil to spark plug.  If it has 2 coils then it may be that one of the coils is sometimes not charging / discharging as it should.  That's probably a bad connection to the coil, or maybe the coil itself is bad.

And yeah, in my experience, intermittent issues are usually electric.  This does not sound like a fuel / valve / timing issue, especially as you say you just worked on those things.

Both coils are brand new too, they came pre-wired direcrly into coils, so I just had to twist on the spark plug caps.

All of that makes sense though.. sounds like I have to lift the tank and re-check the wiring. What other wiring should I closely inspect?

Is there a way to test the coils? (Aside from swapping sides)

Offline TheCoffeeGuy

  • Posts: 644
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Re: Running on one cylinder intermittently (CB450)
« Reply #8 on: Jun 07, 2018, 10:13:15 »
Both high and low side coils have Ohms readings and ranges found in the Factorty Service Manual
www.thecoffeeguy.ca Not your ordinary Blog site.

1968 Harley Aermacchi ML 125 Rapido, restored
1972 Honda Cl 450 engine rebuild, a day rider soon, now sold
1980 Suzuki GS850GL Street Brat  My other day bike
2000 Harley 1200 Sport S My day bike
1982 Honda CB650 Chopper light

Offline frogman

  • DTT SUPPORTER
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  • Posts: 1965
  • '74 CB360, '71 CB450, '75 CB550SS
Re: Running on one cylinder intermittently (CB450)
« Reply #9 on: Jun 07, 2018, 13:48:47 »
Left side running like that can be a fuel issue since that has the longer hose. Make sure it flows correctly, no kinks or tough bends. If you are using in line filters take them out and see if that helps.

Also, pamcos are known for intermittent issues, take it out and put points back in to verify.

Sent from my SAMSUNG-SM-G891A using Tapatalk
« Last Edit: Jun 07, 2018, 13:50:47 by frogman »