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Author Topic: Could this cause fuel delivery problems?  (Read 1197 times)

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Offline robdrobd

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Could this cause fuel delivery problems?
« on: August 30, 2011, 06:37:43 AM »
1976 cb750k. My fuel line dips down quite a bit before reaching the carbs. I am having no problems when the bike gets throttle, but when coasting at low speeds the bike almost feels like it is skipping. Could fuel be having trouble getting to the carbs when there is no throttle? Here is a pic
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Offline WarwickE36

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Re: Could this cause fuel delivery problems?
« Reply #1 on: August 30, 2011, 06:51:14 AM »
Looks a bit pinched, which could cause fuel starvation.  However, probably isn't the cause for the problem you are troubleshooting.  That being said it should be addressed before you move on with the diagnostics.  Always fix a known problem before moving on to an unknown.
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Offline robdrobd

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Could this cause fuel delivery problems?
« Reply #2 on: August 30, 2011, 06:57:46 AM »
It seems like it's going uphill a bit
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Offline Gordon

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Re: Could this cause fuel delivery problems?
« Reply #3 on: August 30, 2011, 07:00:53 AM »
The kind of curve you need to worry about in a fuel line is an upside-down "U" bend where air can get trapped at the top, not the kind in your picture.  Missing at low speed isn't typically a symptom of a fuel delivery issue.  That problem would show itself at high speed/high rpm when the engine needs more fuel than is being provided. 
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Offline ekpent

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Re: Could this cause fuel delivery problems?
« Reply #4 on: August 30, 2011, 07:03:38 AM »
750's can run quite awhile even with the petcock off as I am sure we have all found out at least once.Doubt that would cause the issue you are having with the coasting.Starvation would rear its head more at higher revs I would think.     WHOOPS - Looks like Gordon and I are thinking along the same lines  :)
« Last Edit: August 30, 2011, 07:05:12 AM by ekpent »
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Offline robdrobd

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Could this cause fuel delivery problems?
« Reply #5 on: August 30, 2011, 08:02:52 AM »
Hmmmm. Well thought I would ask before I did anything drastic.
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Offline flybox1

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Re: Could this cause fuel delivery problems?
« Reply #6 on: August 30, 2011, 08:16:29 AM »
a clear fuel line might reveal a 'bubble' in the high portion of your fuel line routing.
its a gravity system.  air will always seek the highest point.
just 'burp' your line to expel the bubble.
w/ PC open,  lean your bike in the same direction as the flow of gas.
the fuel line should fill and expel the bubble upwards. more air shouldn't be introduced into they system again unless you remove the line from your carbs or decide to blow into your overflow tubes.  ::)
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Offline wanackg

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Re: Could this cause fuel delivery problems?
« Reply #7 on: August 30, 2011, 08:43:09 PM »
Only if its kinked or, as previously said, there is an air bubble in the line.
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