Topic: 1978 CB550 carbs

[stevenwr]

I'm rebuilding my PD46C carbs and was wondering which groove the clip goes into the needles? The bike has stock airbox, main & slow jets and 4-2 exhaust.

[TwoTired]

The stock needle position is the 3rd groove from the top for that model.
But, it is very unlikely to be ideal at that setting with the exhaust change.  Same is true for the main jet size.

I don't think there is a plug and play solution.  Either trial and error with the risk or cooking the engine, or some dyno time to determine correct A/F ratio.

Cheers,

[stevenwr]

Would the exhaust make that much of a difference, it's not a performance exhaust, old school flared mufflers.
When I took the carb apart I found #1 needle clip on the first groove and the other three in the second groove.

[TwoTired]

Would the exhaust make that much of a difference,

Yes, it does on this model.  The stock muffler pressure was used to allow very lean mixture ratios provided by the carbs.  Change the exhaust and the carbs must be adjusted for that change, or the engine will run lean/hot, which cooks the valve guide seals and the exhaust valve guides.

You can thank the EPA's influence on Honda being accepted for importation for that.

Sorry about that.