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Author Topic: One header pipe not hot  (Read 1410 times)

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Offline gregripko

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One header pipe not hot
« on: July 04, 2016, 05:30:14 PM »
Noticed today that one of the pipes was warm... Not hot like the other three. I sprayed cleaner on each pipe and it evaporated except for cylinder four. I put plug on engine head while running and I can see a strong steady spark. Cleaned jetting before. Seems to have poor acceleration.

CB550K
« Last Edit: July 04, 2016, 05:31:57 PM by gregripko »
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Offline BomberMann650

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Re: One header pipe not hot
« Reply #1 on: July 04, 2016, 05:50:57 PM »
When was the last 3k service?  And hows that A/F mix on four compared to the others?
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Offline ekpent

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Re: One header pipe not hot
« Reply #2 on: July 04, 2016, 05:57:13 PM »
changing the spark plug is an easy first thing.
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Offline gregripko

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Re: One header pipe not hot
« Reply #3 on: July 04, 2016, 05:57:52 PM »
Changed spark plug and it didn't change anything
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Offline robnola44

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Re: One header pipe not hot
« Reply #4 on: July 04, 2016, 06:00:55 PM »
when you pulled the plug did the idle change at all?
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Offline gregripko

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Re: One header pipe not hot
« Reply #5 on: July 04, 2016, 06:21:40 PM »
I pulled the cap off 4 just now and it didn't change anything... Pulled 1 and it sounded like it was going to die... But when the cap is near the top of forth plug you can hear the spark firing
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Offline gregripko

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Re: One header pipe not hot
« Reply #6 on: July 04, 2016, 06:29:09 PM »
Plugs 1-4 in that order.... 4 is giving me trouble
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Offline robnola44

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Re: One header pipe not hot
« Reply #7 on: July 04, 2016, 07:10:52 PM »
this just happened on mine except it was cylinder 1 and it ended up being the tiniest spec of dirt in the carb but...pulling the plug and it not changing the idle could be spark, fuel, or compression, do a compression check, you know you have spark, and last is the fuel. you said you cleaned the jets but with these carbs you REALLY have to clean them above and beyond.
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Offline scottly

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Re: One header pipe not hot
« Reply #8 on: July 04, 2016, 07:33:24 PM »
Quote from: gregripko on July 04, 2016, 05:57:52 PM
Changed spark plug and it didn't change anything
What does the new plug look like?
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Offline gregripko

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Re: One header pipe not hot
« Reply #9 on: July 04, 2016, 07:38:21 PM »
Number 4
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Offline scottly

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Re: One header pipe not hot
« Reply #10 on: July 04, 2016, 07:50:33 PM »
I think you have an ignition problem on 1&4. This is what a weak spark looks like; wet and relatively clean. With a wasted spark setup, one side of the coil produces a reverse polarity spark, which is weaker than the other side. The #4 is getting the weaker spark of the pair, but there is evidence of problems on the #1 plug as well. 
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Offline gregripko

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Re: One header pipe not hot
« Reply #11 on: July 04, 2016, 08:02:44 PM »
It's there a solution for that? My number #1 pipe is bluing and very hot compared to the other pipes but 2 and 3 are coloring as well it's just not as dramatic. Using a timing light it timed up fine when connected to spark wire 4 (strobe light)
« Last Edit: July 04, 2016, 08:34:50 PM by gregripko »
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Offline Terry in Australia

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Re: One header pipe not hot
« Reply #12 on: July 05, 2016, 03:33:01 AM »
Well it has poor acceleration because it's only running on 3 cylinders. I'm guessing that it's a blocked pilot jet, I know you said you've cleaned the jets, but to explain, you need to remove them all, spray them with carb cleaner and use compressed air to make sure they're not still blocked. (hold them up to the light, if you can't see daylight through them, they're still blocked)

Remove the mixture (air) screws then use the compressed air to run through all of the circuits to ensure there's no crap blocking the flow of air, or fuel in any of the carbs. if it's got a nice fat spark, I doubt it's an ignition problem. I've got the same problem with a 750 I built for a customer, I'll be pulling the carbs again this weekend. Cheers, Terry. ;D
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Offline gregripko

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Re: One header pipe not hot
« Reply #13 on: July 05, 2016, 07:01:52 AM »
Random question... When going full throttle or at least opening throttle most of the way, would that not require slow jet and only be using main? Wouldnt I notice more power? At this point I'm thinking that fuel isn't getting to spark plug so I'll have to recheck things and hope I find a solution.
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Offline flybox1

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Re: One header pipe not hot
« Reply #14 on: July 05, 2016, 07:40:46 AM »
Quote from: gregripko on July 05, 2016, 07:01:52 AM
Random question... When going full throttle or at least opening throttle most of the way, would that not require slow jet and only be using main?
What mechanism in your carbs shuts off fuel flowing through the idle circuit or pilot jet at WOT?

Its a cumulative supply as you increase throttle position.
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Offline BomberMann650

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Re: One header pipe not hot
« Reply #15 on: July 05, 2016, 07:41:37 AM »
Quote from: scottly on July 04, 2016, 07:50:33 PM
I think you have an ignition problem on 1&4. This is what a weak spark looks like; wet and relatively clean. With a wasted spark setup, one side of the coil produces a reverse polarity spark, which is weaker than the other side. The #4 is getting the weaker spark of the pair, but there is evidence of problems on the #1 plug as well.

I am Interested in the remedy too!  Fix it or replace it?
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Offline gregripko

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Re: One header pipe not hot
« Reply #16 on: July 05, 2016, 08:10:11 AM »
Quote from: flybox1 on July 05, 2016, 07:40:46 AM
Quote from: gregripko on July 05, 2016, 07:01:52 AM
Random question... When going full throttle or at least opening throttle most of the way, would that not require slow jet and only be using main?
What mechanism in your carbs shuts off fuel flowing through the idle circuit or pilot jet at WOT?

Its a cumulative supply as you increase throttle position.


That def makes sense.... Ill have to take a look at carb and make sure everything is clear and functioning properly
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Offline flybox1

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Re: One header pipe not hot
« Reply #17 on: July 05, 2016, 08:19:44 AM »
Idle plug chop with new plugs.
Post pictures of the results.
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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)
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"Knowledge without mileage equals bullsh!t" - Henry Rollins

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Offline gregripko

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Re: One header pipe not hot
« Reply #18 on: July 06, 2016, 11:12:57 PM »
*SOLVED*

Pulled the carb bowl and it was bone dry.... Fuel problem.... Thought there was a blockage somewhere but it ended up being float height problem. Tang was so high it was closing off fuel. Had a spare float and replaced it and fuel was flowing. :)
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Offline Terry in Australia

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Re: One header pipe not hot
« Reply #19 on: July 07, 2016, 12:57:21 AM »
Well done mate, yep, they don't run well with no gas..... ;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 scottly

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Re: One header pipe not hot
« Reply #20 on: July 07, 2016, 09:26:01 PM »
Greg, I guess the wetness on the #4 plug was oil, and not fuel? Did it smoke a bit after running?
There is a big difference in the color of the 2-3 plugs, and the 1-4 plugs. It might be a good idea to do a "clear tube" test on all four float bowls.
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Offline gregripko

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Re: One header pipe not hot
« Reply #21 on: July 07, 2016, 10:58:32 PM »
Going to run it a bit and see if plugs normalize a bit
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