Author Topic: 74 CB350F Carb Question  (Read 907 times)

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Offline GizmoDuck

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74 CB350F Carb Question
« on: September 19, 2015, 07:10:08 AM »
In the pick below you can see the fuel hose connected to the carb and to the left of it are two other brass hose fittings, that I assume are drains, should they both have rubber hoses on them and what do they actually do?

Offline flybox1

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Re: 74 CB350F Carb Question
« Reply #1 on: September 19, 2015, 04:50:15 PM »
Air vents to equalize pressure as carbs drain and fill....
'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

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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 chewbacca5000

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Re: 74 CB350F Carb Question
« Reply #2 on: September 19, 2015, 04:58:30 PM »
Air vents to equalize pressure as carbs drain and fill....

Flybox for the win.  Just what he said.  They equalize pressure.  Mine are missing wonder if that could cause an overflow issue?

Offline flybox1

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Re: 74 CB350F Carb Question
« Reply #3 on: September 19, 2015, 05:04:24 PM »
No,  ut if they were clogged, they will cause slow filling of the bowls...
'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 chewbacca5000

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Re: 74 CB350F Carb Question
« Reply #4 on: September 19, 2015, 05:12:45 PM »
No,  ut if they were clogged, they will cause slow filling of the bowls...

O well here's to hoping.  Round 2 tank / carb clean.  Think I just going to RedKote this sucker and be done with it.

Offline gtmdriver

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Re: 74 CB350F Carb Question
« Reply #5 on: September 20, 2015, 11:20:40 AM »
If the vent pipes are missing water can get in to the float chambers. They should loop up then down again or lead somewhere where nothing can drop in.

The drain tube are the ones which come out of the bottom of the float chambers. They should all have tubes on too.


Offline GizmoDuck

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Re: 74 CB350F Carb Question
« Reply #6 on: September 21, 2015, 04:07:42 PM »
So one fuel connector, two air vents next to that, and then four drains at the bottom of the float chambers?

Offline gtmdriver

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Re: 74 CB350F Carb Question
« Reply #7 on: September 22, 2015, 06:39:50 AM »
Yes. That's it.

I used bio-fuel proof Nitrile rubber for the fuel and drain lines and I used PVC (because I ran out of nitrile) for the vent tubes.

The fuel line should be 5mm I.D. and the drains and vents should be 3mm I.D.