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

[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.

[LesterPiglet]

I've heard bad reports about Keyster and always have had original replacements recommended.

[pptom]

I would think an exhaust change would make the bike run lean if anything, what size are your main jets? are the floats sticking open allowing too much fuel in? did you set them correctly? needle jets too small? rubber O rings good fit on the main jets?
Can't think of much else - generally 'mods' will make the engine run more lean.

[Bitsa (Ralph Wright - RIP)]

Hi All,
Back in the 70s my mate had a 500/4 and when the original pipes rotted he replaced the system with a 4 into 1 motard.As I remember going through southend his bike popped and farted around so rich it coughed out black smoke.When I did the same with my 750 I remember up and down to plug test and finally got set with 112.5 main jets.In those days easy to get.Its a matter off flat out kill coast and plug check providing float heights and air intake plus all airways clear.
Cheers
Bitsa

[buzzens]

Once again thank you all for your replies. I too have heard about Keyster carb kits been a problem, they list the jets as per standard CB550F. The kits I got are from a company in Canada; Cirrius i think was the company name or something similar. I can't find any genuine kits anywhere at the moment, so I think my chances could be slim, maybe look out for a 2nd hand set of carbs.
Cheers

[buzzens]

I have now finally traced and purchased NOS 3 needle & jet sets which now completes all the parts I require to put the carbs back to original Honda from the Keyster kits, this includes NOS main and slow running jets purchased quite some time ago. Just got to find the time to do it now...

[LesterPiglet]

I hope that sorts your problem.