Topic: carb question 74cb550

[kmaslowski]

I just purchased a 74 cb550 in need of some major carb work. Pulled them apart to clean/rebuild and found a mess, homemade float pins in 2 of the 4 carbs, busted tower where the float pins goes into, lots of varnish etc etc. I found a set of carbs on ebay for a 75-77 cb550F and not sure if i can use them. They look identical to mine. 2 questions: 1) can i use these 75-77 carbs on my 74 cb550k?  2) if the jets etc are different in the 75-77 carbs, can i just get a rebuild kit for my 74 carbs (i have) and install it?  Thanks, any help is greatly appreciated!

[Lars]

You can buy replacement kits all the time on eBay. Only part not usually in those kits, is the brass pipe which the needle goes into. You get them from your Honda dealer.

Replace all the o-rings, including those on the two T-parts into which the two fuel lines are attached. Also replace the fuel lines if they are old and a bit stiff.

If your stud is broken, where you bolt on the floats, you have a more delicate problem. Not sure if you can weld them on.

You have most likely a CB 550 K model, the carbs to a F model will fit on and the bike should run. I have heard, but never measured, that one of the differences is the length of the manifold, a bit longer on the F model. Should give a better mixture of air and fuel and make the engine run stronger. IF this is correct, you might have a little trouble fitting the airbox rubber tubes on the carb, it is pretty tight in that area as it is.

Lars

[kmaslowski]

Thanks for all the great info guys! I have my original intake manifold I can use with the F series carbs, looks like the carbs should bolt right up to it.
I came acroos a site selling NEW carbs for 749.99 dollars, a bit much to spend but I found it interesting that they do specify the same carbs to be used on a 75-77 F series bike. Obviously which leads me to believe I should be ok. Thanks again, really glad I found this forum, it's going to prove to be invaluable. 

[Lars]

Love to hear that - we are invaluable. Tell my wife!!!!!!!!!!!!

[kmaslowski]

Update on my progress. Carbs from ebay came in, soaked em in gunk, rebuilt using the rebuild kits I purchased. Only issue was float pins were really stuch on 2 of the 4 carbs, while removing 1 pin, broke the float pin tower  That will teach me to stay up til 2:00am working on it! I did jb weld it, drilled a hole in the center of the tower as well as in the body so the jb weld could form a "pin" and help hold it. Bolted carbs back on and fired it up! It runs relatively well. Only issue i seem to be having is idle isnt consistant. I snap the throttle and sometimes the idle comes back down to normal. other times it's idling higher rpm, etc. I know it's not in throtle binding or anything like that. Just cant seem to get the idle worked out right, but otherwise runs great. Replaced points/condenser and timed last night and runs better, but not perfect. Does this sound like a potential air leak?? Any thoughts on how to test for a air leak??  Anybody know what the normal operating temp is? I have an infrared temp guage and in showing around 210 or so depending on where you point it. Thanks!

[Caferacernoc]

Engine not consistantly coming back down quickly to idle usually indicates the carbs need synching.

[ryder60]

Synching is a must after a rebuild like yours.