Author Topic: 1981 CB650 Carb Question  (Read 1219 times)

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Offline annerstine

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1981 CB650 Carb Question
« on: December 13, 2015, 03:05:15 PM »
I just bought an 81 CB650C, the bike cranks up but when you turn the fuel petcock to on the carbs start spilling gas. So i pulled the carbs off and I noticed that it looks like there is one missing hose between carbs 3 and 4 and the hose between 1 and 2 is rotten and almost coming off...What does this hose do? at first I thought it was the fuel distribution hose but now I'm wondering if it has to do with the vacuums. Any advice would be greatly appreciated!
« Last Edit: December 13, 2015, 03:22:05 PM by annerstine »

Offline harisuluv

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Re: 1981 CB650 Carb Question
« Reply #1 on: December 13, 2015, 03:37:31 PM »
Those are just tubes that equalize pressure.  Example (shotgun a beer:  the second hole allows it to empty or fill faster, in this case the fuel level in bowls)

At the bottom of the bodes (or at the top of your picture) there are clearly  two aluminum tubes between the carbs.  The smaller one is the accelerator pump circuit.  The larger one is the fuel line.

Offline annerstine

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Re: 1981 CB650 Carb Question
« Reply #2 on: December 13, 2015, 04:02:27 PM »
thanks for the reply harisuluv! so would the fact that the tubes are rotted and/or not missing cause the bike to run poorly or have anything to do with the carbs spilling gas?

Also, I posted some more pics just to make sure we're talking about the same thing, notice the rubber hose missing from the 2 protruding metal cylinders.


Offline harisuluv

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Re: 1981 CB650 Carb Question
« Reply #3 on: December 13, 2015, 04:32:09 PM »
Yes we are talking about the same thing.

Your problem is due to the float and valve not shutting off gas flow.  Therefore, gas keeps coming in until it reaches the overflow level and then it starts to drain out.  For your bike, this can be fixed with new float valves.  You won't need to set the float height because those floats have no adjustment (plastic).

Offline SOHC4 Cafe Racer Fan

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Re: 1981 CB650 Carb Question
« Reply #4 on: December 14, 2015, 09:35:25 AM »
annerstine,

Don't let hariuluv's avatar fool you.  He doesn't just rebuild carburetors, he makes them like new. 
1975 CB550K1 "Blue" Stockish Restomod (http://forums.sohc4.net/index.php?topic=135005.0)
1975 CB550F1 frame/CB650 engine hybrid "The Hot Mess" (http://forums.sohc4.net/index.php/topic,150220.0.html)
2008 Triumph Thruxton (http://forums.sohc4.net/index.php/topic,190956.0.html)
2014 MV Agusta Brutale Dragster 800
2015 Yamaha FZ-09 (http://forums.sohc4.net/index.php/topic,186861.0.html)

"There are some things nobody needs in this world, and a bright-red, hunch-back, warp-speed 900cc cafe racer is one of them — but I want one anyway, and on some days I actually believe I need one.... Being shot out of a cannon will always be better than being squeezed out of a tube. That is why God made fast motorcycles, Bubba." Hunter S. Thompson, Song of the Sausage Creature, Cycle World, March 1995.  (http://www.latexnet.org/~csmith/sausage.html and https://magazine.cycleworld.com/article/1995/3/1/song-of-the-sausage-creature)

Sold/Emeritus
1973 CB750K2 "Bionic Mongrel" (http://forums.sohc4.net/index.php?topic=132734.0) - Sold
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