Topic: CB550F Choke Question

[Zora]

Hi,

I'm in the process of rebuilding the carbs on my '77 CB550F. The bike is new to me but hasn't been run in years. After taking the carbs off the bike I have found there is a little spring loaded flapper door on the back side of each butterfly used to choke the bike. Three of the four doors have broken springs allowing them to just flap around. The fourth one seems to work fine.

I'd be surprised if I could find replacement springs so what is the next best solution? Should I break the remaining spring parts off and just let the little doors flap around? Or should I drill out the pin holding the door to the butterfly and remove all the doors? I would still leave the butterfly in the carb so I could choke it when needed.

Thanks.

[Bodi]

The choke won't work as well with those flaps unsprung, cold starting might be more difficult. But don't worry about it. Leave the working one as is. The springs probably made it though the engine without drama but might have caught between piston and cylinder and scored a cylinder wall, but there's SFA you can do about that except o/s pistons and a rebore: if it runs OK then leave it alone. The flaps are to avoid extreme vacuum with the choke closed, this can suck a ridiculous amount of fuel from the carb and cause flooding.

I don't recall which way the flaps hang. If they block the throat with choke off you could remove them, but I doubt this would really cause much trouble anyway.

[Zora]

Bodi - Thanks for the advice. I ended up drilling the pins out and taking the flapper doors off. I'm not too worried about cold starting as it doesn't get real cold here in SoCal. Two carbs are done but the other two will have to wait until next weekend.

~Z