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Author Topic: Are 550 carbs jetted a little rich from the factory?  (Read 576 times)

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Offline B.O.X.N.I.F.E.

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Are 550 carbs jetted a little rich from the factory?
« on: June 13, 2011, 04:21:36 PM »
When I got my 1974 550 I had a rich problem past half throttle. I pulled them apart and found no non-stock jet parts. The only modification was a 4-1 MAC exhaust. In the end I had to lean the needle's out 1 clip position. 15k miles later the plugs were still a nice even light brown. Problem solved.

Now that I'm building another of the same year should I preemptively lean out the needles? This bike has a stock 4-4.
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1974 CB550

32 days and 5,536 miles on a CB550...

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and a couple years later, 38 days and 9,102 miles...

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Offline TwoTired

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Re: Are 550 carbs jetted a little rich from the factory?
« Reply #1 on: June 13, 2011, 07:10:13 PM »
Stock needle clips were in the 4th from the top.

They do run rich at idle throttle position.  They have to, so that opening the throttle with it's sudden in rush of air doesn't cause the engine to fuel starve.
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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.
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