Topic: Compulsive Carburetor Questions Re: '76 CB550F

[TwoTired]

I have a 1976 cb550f. as far as i can tell all internal carb jets and needles were stock except at some point someone put 100 mains in. all the orings were shot so i ordered a set a carb rebuild kits, i in return was given the d26 needles in a kit for the 500/550. with all parts replaced and the jet needle on the same middle 3rd groove the bike is hitting a flat spot at 6500- 7000rpm. i am willing to move the needle 1 more down, richening the mix. however im not sure if this is because i have better seals with the orings, were before i may have been running richer from leaking around the oring, or because i have been sold the wrong kit for my bike. ill double check all the numbers when i get home

Is your exhuast system and air filter stock?  Carbs were tuned with these factors in mind. 

d26 needles are NOT Honda part numbers.  Did you compare/measure the old needle's dimensions with the replacements?

What was wrong with the parts that were in the carbs originally?

Cheers,

[sophisticat]

1976 Honda Cb550f all stock expect, mac 4 into1 exhaust, Uni foam pods, Dyna 3.0 ohm coils and Dyna Graphite coil wires. I was sold K&L rebuild kits for my bike, Part # 18-2422, labeled for a 74-77 CB550k. Stock Keihin jet needles were 273004, set to 2nd from leanest clip, with the 4 into 4 exhaust i had to move the clip to the middle position 1 clip richer. The rebuild kit came with 100 mains, 38 idle and D26 jet needles. Also the fuel mixture screw was hollow with a cross drilled hole, different from the solid stock one i have. With the changes to the bike, and the carb rebuild, I placed the D26 jet needle on the middle clip and it feels lean. the biggest difference i noticed between the stock needle and the D26 needle is the taper. The stock needle is a longer more narrow taper. The D26 is a shorter wider taper. Im not sure if I got sold the wrong kit or not. I'm taking it to a local shop tomorrow, I think it will be worth the labor to have them do the jetting.

TT do you have the information and or a copy of the shop manual that shows the stock carb 069a's specs and stock needle clip position.

[TwoTired]

The stock settings are in the a chart in the carb FAQ.
However, the settings for a Mac 4 into 1 and uni pods will in no way be the same as stock config for an F model.

The stock settings were tailored for the stock induction/air filter, and a far more restrictive 4 into 1 muffler.

Essentially, you modified the carbs to that of 022A carbs for the K.  The slide needle should in the 4th clip position for that configuration.  I've no idea if that will fine tune your situation, having custom exhaust and an air induction engineering change.

Good luck!