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Author Topic: 78 CB550 restoration  (Read 1480 times)

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Offline stevenwr

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78 CB550 restoration
« on: July 19, 2011, 01:19:37 PM »
 I recently purchased a 1978 CB550 in decent shape. I'm cleaning it up just to get it on the road. I cleaned the carbs and put a carb rebuild kit it to it. I started it up last night to sync the carbs but fuel started poring out the air box drain. Any suggestions would be greatly appreciated. When the bike is on the road I'll post photos.

P.S. great site.
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Offline Bankerdanny

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Re: 78 CB550 restoration
« Reply #1 on: July 19, 2011, 03:25:23 PM »
Sticking floats would be the first thing to check. Does gas come out of the float bowl overflow tubes (the ones that stick out of the bottom of the carbs) too?
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Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline stevenwr

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Re: 78 CB550 restoration
« Reply #2 on: July 19, 2011, 03:46:08 PM »
No, the fuel just pours out of the air box. I think your right about the sticking float. I'm going to remove the boots going to the air box and see which carb(s) the fuel is coming out of.
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Offline TwoTired

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Re: 78 CB550 restoration
« Reply #3 on: July 19, 2011, 04:07:26 PM »
Check to see if the carb overflow drain tubes are plugged.  Overflowing carbs should drain there first and then to the airbox or engine intake valve if the overflow tubes are blocked.

Check for gas in the oil.  Overflowing carbs can cause that.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline stevenwr

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Re: 78 CB550 restoration
« Reply #4 on: July 20, 2011, 04:38:34 AM »
I drained and removed the float bowls. None of the floats and float valves are sticking. I checked the over flow drain tubes and none of them are plugged. I then removed the rubber boots connecting the carbs to the air box so later today I'll fire it up again to see exactly where the gas is coming from and which carb(s). I'll aslo check the oil to see if there's any gas in it.

Thanks.
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Offline tedone

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Re: 78 CB550 restoration
« Reply #5 on: July 20, 2011, 06:11:35 AM »
Just a heads-up.
The 78 550 carbs only have one fuel line feeding them. The other nipple smaller nipple nearby is for vent.
Your not feeding that gas also, are you? (ask me how I know).
My ride did not have fuel lines hooked up when I bought it, and I was misled by looking at the 76 carbs that take 2 fuel lines.
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Offline stevenwr

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Re: 78 CB550 restoration
« Reply #6 on: July 20, 2011, 03:41:22 PM »
Before firing it up I noticed the two lines coming from the carbs and only one port on the fuel tank, that's what brought me to this site. I put gas into the correct line on the carb.
 Well I fired up the bike with no air box #1-3 carbs were leaking fuel from the overflow tubes and the #1 carb was also pouring fuel from one of the small brass tubes pointing in towards the air box (intake portion of carb). I removed the carbs and checked the float levels, which I should have done before hand ::). #1 float 7mm, #2&3 10mm and #4 13.64mm. I set all 4 too 14.5 mm. After work I'll put the carbs back in and fire it up.
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Offline stevenwr

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Re: 78 CB550 restoration
« Reply #7 on: July 20, 2011, 11:41:05 PM »
I'm a little uncertain of the float level height, my manual states 22mm but I've read it should be set to 14.5 mm and I've also found a site saying 12.5 mm. Anyone know the proper float level height for a 1978 CB550?
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Offline TwoTired

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Re: 78 CB550 restoration
« Reply #8 on: July 21, 2011, 12:11:50 AM »
Your manual must be the Clymer.  22mm is for the early carbs, not the PD style.
I set my 78 CB550K floats to 14.5mm.  Actually, that's where they were set from the factory.  Runs well.

Cheers,
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline stevenwr

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Re: 78 CB550 restoration
« Reply #9 on: July 21, 2011, 04:01:24 AM »
Sweet...thanks for the info.
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