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Author Topic: 72 500 not warming 3 and 4  (Read 1082 times)

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ScottB

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72 500 not warming 3 and 4
« on: June 23, 2009, 01:10:40 PM »
Hey -

I could use some help here, I've searched but couldn't find anything close.  As stated, I can't get cylinders 3 and 4 to fire.   

I'm running a 4 into 1 with the factory box and factory carb settings.  I haven't adjusted the valves yet (waiting on the right feeler gauges to come in) but I have synced the carbs and installed and Dyna S.  I've checked that fuel and spark are good to go. 



Could this be a compression issue?  Any ideas before I cut my arm off to make the pain go away? 

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Offline CBGhia

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Re: 72 500 not warming 3 and 4
« Reply #1 on: June 23, 2009, 01:17:08 PM »
3 and 4 are using the same fuel source.  In most cases, if the 2 cylinders next to each other (1and 2 or 3 and 4) are not firing it is a fuel source issue.  You might want to make sure that the fuel line is not pinched somewhere.   
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CB550 Cafe, GL1000, Buell Ulysses
Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

ScottB

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Re: 72 500 not warming 3 and 4
« Reply #2 on: June 23, 2009, 01:18:22 PM »
Thanks - I have confirmed that I have fuel coming out of the drain plug. 
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Offline CBGhia

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Re: 72 500 not warming 3 and 4
« Reply #3 on: June 23, 2009, 01:22:28 PM »
You might double check just to be sure.  A pinched line can allow a small amount of fuel to enter the carbs but not enough to allow it to work properly.  It would not fire right, or at all, and you might still see fuel come out of the drain screws.  

There could be other things, but for 2 cyclinders right next to each other sharing the same fuel line...
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CB550 Cafe, GL1000, Buell Ulysses
Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

ScottB

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Re: 72 500 not warming 3 and 4
« Reply #4 on: June 23, 2009, 01:26:28 PM »
Got it - I'll check for flow.
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Offline TwoTired

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Re: 72 500 not warming 3 and 4
« Reply #5 on: June 23, 2009, 01:29:36 PM »
Are 3&4 spark plugs wet or dry?
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

ScottB

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Re: 72 500 not warming 3 and 4
« Reply #6 on: June 23, 2009, 01:37:10 PM »
Two - not sure at this moment.  I just hooked up a single line of fuel to the 3 and 4 carbs but before I could fire the bike fuel was spilling out of the front of the carbs and the overflow.  Any ideas there? 
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Offline mlinder

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Re: 72 500 not warming 3 and 4
« Reply #7 on: June 23, 2009, 01:41:17 PM »
Floats stuck or float needles are facked.
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Offline TwoTired

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Re: 72 500 not warming 3 and 4
« Reply #8 on: June 23, 2009, 01:42:43 PM »
Stuck floats/ float valves in the carbs?

Check your oil for fuel contamination and your carb bowl overflow tubes for blockage.
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

ScottB

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Re: 72 500 not warming 3 and 4
« Reply #9 on: June 23, 2009, 01:48:00 PM »
Thanks guys - I'll tear'em down tonight.
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Offline CBGhia

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Re: 72 500 not warming 3 and 4
« Reply #10 on: June 23, 2009, 01:59:12 PM »
before you tear apart the carbs (they may need it) try wacking the float bowls with a plastic handle of the screwdriver.  It may un-stick the floats and stop the leak.  Sometimes they just get stuck from non use. 

It may not work and you will still have to tear em down, but it only takes a few seconds to try.   ;D
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CB550 Cafe, GL1000, Buell Ulysses
Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson
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