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Author Topic: 1978 CB750K fuel tank lines  (Read 1340 times)

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Offline Doggie

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1978 CB750K fuel tank lines
« on: January 11, 2014, 08:53:01 PM »
When installing my fuel tank for my 1978 CB75K, I don't remember what hooks up to the fitting in the bottom center of the tank? The only hose I have left is a small vent hose from the carb and the fitting on the tank is 3/8". Am I missing something?
                                        Thanks, Doug
                     
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Black 750K8

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Re: 1978 CB750K fuel tank lines
« Reply #1 on: January 12, 2014, 12:03:28 AM »
That fitting is a over flow if you spill fuel or rain gets in around the fuel door. The service manual shows how to route it.









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Offline flybox1

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Re: 1978 CB750K fuel tank lines
« Reply #2 on: January 12, 2014, 09:26:54 AM »
+1
Route it down between the engine cases and the rear swingarm so any spillage goes right to the ground...
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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)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline Doggie

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Re: 1978 CB750K fuel tank lines
« Reply #3 on: January 12, 2014, 02:53:33 PM »
Thanks for the answers to my problem. This is one bike that I don't have the service manual for.
                                                  Doug
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Offline martin99

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Re: 1978 CB750K fuel tank lines
« Reply #4 on: January 12, 2014, 03:28:06 PM »
The stock routing (on an F2 anyway) is along the top frame rail finishing up at the rear of the bike. I get the overflow part, but doesn't the tube also have a secondary function to ensure adequate venting for the fuel cap? The tank flap sits pretty cosy on it's rubber gasket.
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Build threads:
77 750F2 Refresh Project http://forums.sohc4.net/index.php?topic=144075.0
TRIBSA http://forums.sohc4.net/index.php/topic,160296.0.html

1977 CB750 F2
1958 Norton Model 99
2011 Triumph Street Triple 675

Black 750K8

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Re: 1978 CB750K fuel tank lines
« Reply #5 on: January 12, 2014, 04:23:59 PM »
Quote from: Doggie on January 12, 2014, 02:53:33 PM
Thanks for the answers to my problem. This is one bike that I don't have the service manual for.
                                                  Doug

Doug look at the top of the page you are reading this on for the shop manual. It says download motorcycle manuals
Below is a link for the 750 ;).
http://minus.com/lbxEWtmN0RaClv
« Last Edit: January 12, 2014, 04:25:51 PM by Black 750K8 »
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Black 750K8

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Re: 1978 CB750K fuel tank lines
« Reply #6 on: January 12, 2014, 04:35:35 PM »
Quote from: oldskoolnuts on January 12, 2014, 03:28:06 PM
The stock routing (on an F2 anyway) is along the top frame rail finishing up at the rear of the bike. I get the overflow part, but doesn't the tube also have a secondary function to ensure adequate venting for the fuel cap? The tank flap sits pretty cosy on it's rubber gasket.

No door gasket (on a 78K anyway) and it is by no means airtight. Thus the drain for rain.
http://www.cmsnl.com/honda-cb750k8-four-usa_model14397/partslist/F12.html#results
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Offline Doggie

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Re: 1978 CB750K fuel tank lines
« Reply #7 on: January 12, 2014, 09:58:03 PM »
You guys are great. Thanks for the help. I'm missing the whole vent tube, so thats what puzzled me. I'll have to pickup some hose and make one. The tank was the last thing to go on and my ride is done.
                                Thanks again, Doug
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Offline lucky

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Re: 1978 CB750K fuel tank lines
« Reply #8 on: January 13, 2014, 10:40:38 AM »
Do not use 40 year old hoses!
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