Author Topic: Carb. Leaking ?  (Read 1857 times)

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Offline rddcw

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Carb. Leaking ?
« on: July 01, 2015, 07:35:25 PM »
Just recently purchased a 75' CB750 K5. I did notice that the Right outside Carb. is leaking from the overflow tube when the motorcycle is not running and the fuel petcock is off. It drips more when the bike is on the center stand.

Pulled carb. bowl off. Float is free and raises/lowers fine. Pulled the float seat off after removing float. Seat and needle look good but cleaned both to make sure. Changed the gasket too. Inspected float-no cracks. Overflow tube in carb. bowl is good too. When the float assembly was off as well as the seat and needle, gas was steadily dripping from carb. seat opening?

Re-installed float assembly but still dripping. Only when I physically raise the float does the drip stop. Re-assembled carb. Thought I had it for the bike didn't have any gas coming out of overflow tube, but "intermittently" it still leaks?

Do you Tech. Guys have any ideas?

Offline eigenvector

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Re: Carb. Leaking ?
« Reply #1 on: July 01, 2015, 07:44:29 PM »
The fuel line has gas in it, you didn't say how much or how long it dripped - but it's possible that it's just whatever gas is in the fuel line.
Rob
--------------------------------
2018 HD Softail Heritage
1979 CB750K Limited Edition
1977 CB550K
1984 CB700SC Nighthawk
1983 VF750S Sabre

Offline links56

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Re: Carb. Leaking ?
« Reply #2 on: July 01, 2015, 07:47:17 PM »
Does the little pin on the end of the needle still have spring to it? you should be able to push the float lightly and it should spring back to a point.

Offline rddcw

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Re: Carb. Leaking ?
« Reply #3 on: July 01, 2015, 08:15:43 PM »
Eigenvector, that might be it but it's only 1 carb. that drips. And yes it is intermittently. Kind of like it burps out a little gas then stops. Gas puddle when it does happen is probably about a half of bowl in volume?

And link56, the needle has plenty of spring to it.

Offline eigenvector

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Re: Carb. Leaking ?
« Reply #4 on: July 01, 2015, 08:47:26 PM »
All I was really getting at was that the petcock is functioning normally, that it's not pouring out - indicating a major leak.  I would fully expect it to be one carb only.  My guess based on what you just said is that your fuel valve is on it's way out.

Is the fuel level too high in one of the carbs perhaps?  Fuel might be just barely below the level of the overflow - that valve isn't perfect, a little bit will drizzle in from time to time.
Rob
--------------------------------
2018 HD Softail Heritage
1979 CB750K Limited Edition
1977 CB550K
1984 CB700SC Nighthawk
1983 VF750S Sabre

Offline rddcw

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Re: Carb. Leaking ?
« Reply #5 on: July 02, 2015, 03:52:32 AM »
Rob,  I'm assuming when you say Fuel Valve, your referring to the Fuel Petcock?

Offline madmtnmotors

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Re: Carb. Leaking ?
« Reply #6 on: July 02, 2015, 04:03:12 AM »
Two issues:

>Fuel valve is not shutting off properly. There should be no fuel passing through the fuel valve when in the "off" position. Rebuild it with new seals.
>Either float height is wrong in the leaking carb or the float needle and seat need to be replaced (most likely). I would replace all float needles and seats at the same time.
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline rddcw

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Re: Carb. Leaking ?
« Reply #7 on: July 02, 2015, 04:29:03 AM »
Thanks Wilbur,  I'll look into a Fuel Petcock rebuild kit as well as the float seat and needle kit. Any recommendations where to purchase these parts?

Also, Float height adjustment. I have a clear tube w/fitting that I used on my 77' KZ1000 to check the float height. I'm seeing on the Forum that that measurement needs to be 3mm under the float base gasket?

If not using clear tube, what Float measuring gauge would you recommend and at what height on the gauge?

Offline madmtnmotors

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Re: Carb. Leaking ?
« Reply #8 on: July 02, 2015, 04:54:59 AM »
Any recommendations where to purchase these parts?

I would recommend Honda parts for the float needles and seats. At $17 each they are a little pricey though, P/N 16011-375-004

4 into 1 has aftermarket at $5 each, but they can be a roll of the dice. For the price they might be worth a try? http://4into1.com/replica-keihin-2-0-float-needle-valve-assembly-16011-375-004/

The Honda parts will be manufactured to tighter tolerances and often provide the longest service life.
TAMTF...


Wilbur



Projects:
"Evolution": http://forums.sohc4.net/index.php?topic=100352.0
"P.O. Debacle": http://forums.sohc4.net/index.php/topic,126692.msg1441661.html#msg1441661
F2/F3 O-rings: http://forums.sohc4.net/index.php?topic=113672.msg1300721#msg1300721
Cam Tower Studs: https://www.mcmaster.com/#93210a017/=t19sgp
Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                          
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
Branden's leak free top end thread: http://forums.sohc4.net/index.php?topic=107040.0
Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
                                    http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Late model K7/K8/F2/F3 front sprocket cover removal: http://forums.sohc4.net/index.php/topic,178428.msg2072279.html#msg2072279
630 to 530 conversion: http://forums.sohc4.net/index.php/topic,180710.msg2094423.html#msg2094423

Sent from my Tandy TRS-80!

Offline links56

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Re: Carb. Leaking ?
« Reply #9 on: July 02, 2015, 09:41:00 PM »
Regardless of weather the fuel petcock is working properly or not. you should be able to leave it on without having it leak out the overflow. They are 2 separate issues. If the needle is springy can you leave the bowl off and hold the float up with the fuel turned on? fuel should not come out, if it does, the needle and seat need replaced. If it doesn't then the float level is probably too high.

when you take the fuel line directly off the petcock and it is shut off does fuel still come out of it? if so then the petcock needs rebuilt if not you were probably just seeing what fuel was already in the fuel line.


Offline rddcw

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Re: Carb. Leaking ?
« Reply #10 on: July 03, 2015, 03:54:17 AM »
Links56,  When I did remove the float bowl I was able to raise the float assembly up and fuel did Stop dripping. So with that in mind your probably right that the float level is too High.

I didn't get around to removing the fuel lines from the petcock to see if it leaks with it off yet but will.

I know how to adjust the float level by bending the tang but which way either up or down?  What method are you using to check the fuel level?

Are you using a float level gauge or the clear tube method?

Offline links56

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Re: Carb. Leaking ?
« Reply #11 on: July 03, 2015, 08:50:06 AM »
I just use a clear piece of hose. If the carbs have an overflow spigot I just hook it to that and open the bowl drain. Make sure the bike is level and you want it 3mm below the bowl gasket flange. you will want to bend the tang up toward the top of the carb so the float closes the needle earlier than before. Remember a little goes along way, you will probably barely tweak the tang. you can put the carbs in a vice, make sure they are level, and hook a funnel to the fuel line and set all this stuff so you don't have to take it on and off the bike. Check the level first to make sure it is high though.

Offline links56

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Re: Carb. Leaking ?
« Reply #12 on: July 03, 2015, 08:53:47 AM »
If you haven't seen this Flybox1 has posted an awesome picture which shows how it should be hooked up and what it should look like.

http://forums.sohc4.net/index.php/topic,149299.0.html