SOHC.co.uk Forums > CB500/550

CB550f running too rich on Marshall exhaust...help please

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buzzens:
My CB550F1 is running way too rich, fouling all plugs to the point that it will stop. I have during restoration renewed both coils, caps, plugs, carb overhaul kits. carbs have been balanced. I have even dropped the needles onto their lowest settings and even lowered the float height (bad practice, I know). I had never ran the bike before I restored it so not sure if problem existed before. It is, and was, running on electronic ignition, and a new Marshall/Laser Deeptone 4 into 1.
If it requires re-jetting; what jets?

Many thanks for your anticipated replies.

LesterPiglet:
How could the carbs be balanced if it's running so rich as to stop the engine?
Have you a manual? If not I recommend getting one.
Put all the carb settings back to standard and start from there. An exhaust change isn't going to make that big a difference.
Do you have a standard airbox?...and Welcome to the forum.

kendo57:
I bought some carb overhaul kits off Ebay and they had the wrong needles for my F1 as there
are two different carb settings I think depending on model. I would check this first if you
have fitted a carb kit.

Bryanj:
Havent got your leggings or cleaning rag under the seat have you?

buzzens:
Thank you for all the replies. I shall answer the queries. The carbs are balanced ie equal vacuum within range using davida vacuum gauges. I do have both Haynes and Honda workshop manuals. The airbox is standard. The carbs when restored was set to standard settings on rebuild. I used Keyster parts for the rebuild, part no KH 0151F. I have checked for restrictions within the airbox and intake area. I have run the bike with no air filter and removed the airbox, and we all know how awkward that is! Unfortunately I have thrown the original jets etc away so unable to refit the originals; hindsight is a wonderful thing! I did get a comment from a guy who repairs old Hondas' and he said that he has come across Honda 4's fitted with a Marshall need to be re-jetted, but surely not to the degree that mine is running. I agree that there shouldn't be a need to re-jet which makes me think there could be a problem somewhere else; maybe the keyster kits are not as accurate as they should be. Thank you for welcoming me to the forum; it is really appreciated.

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