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Author Topic: 4-1 & needle position  (Read 1063 times)

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

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4-1 & needle position
« on: July 26, 2011, 12:47:50 PM »
Switching my CB550 from a rusty 4-4 to a MAC 4-1. Jetting seems to be a non issue, do I need to be ready to change needle position though?
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Offline dave500

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Re: 4-1 & needle position
« Reply #1 on: July 26, 2011, 01:19:19 PM »
my 550 with 4-1 and type one carbs has 100 main jet,38 slow and standard middle clip position,,i actually dropped the slow jet down from 40.
« Last Edit: July 26, 2011, 01:22:13 PM by dave500 »
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Offline wildcatmahone

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Re: 4-1 & needle position
« Reply #2 on: July 27, 2011, 07:05:29 AM »
+1

No need to change needle clip position just typically one size larger main and slow jet.
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Offline Duanob

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Re: 4-1 & needle position
« Reply #3 on: July 27, 2011, 09:02:14 AM »
Actually wildcatmahonie those are stock size jets for the CB550.

Only your spark plugs will tell you what you need to know, Grasshopper. You will need to do various RPM plug chops to know for sure. If you do a high RPM tell on your plugs and they read a decent tan color then your jet size is fin. If you do an idling tell then your idle/air jets are affected. Just above that your pilot jet is affecting the fuel mix. I think all around city driving affects your needle jet position. Also affecting the needle jets is wear over time. Down load the Carb Manual it is loaded with info on this. Also this diagram helps with when each system is in effect.:




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