Topic: 1974 cb 550 idle circuit

[detaildawg]

Hey all I hope all is well, I have a question.  I just cleaned out the carbs on the 74 550.  I replaced the air box with K and N pods, I rejetted the main to 105 and the slow jet to 42.  It runs great accept for when we put it on the dyno machine, the number 3 carb clogs up the slow jet and the carb goes full lean at idle in about a minute.  I pulled the float bowls back off and the slow jet is glogged yet again.   It is ONLY the number three carb. Any ideas would be greatly appreciated. 

Detail...

[BomberMann650]

Clean your fuel system and verify the float/fuel level.  Inspect float valve and seat for damage/wear that would jam the valve shut.

[Deltarider]

What model is yours? What carbnumber? The year is irrelevant as it tells us nothing. You could have a sticking float needle and try a fuel additive like Seafoam. Is the vent tube of #3 open?

[Bankerdanny]

If it is a 74 it can only be a K as the 550 didn't come out until 75.

If the slow jet is actually clogging then you need to replace all your fuel lines including the ones that connect the 2 pairs of carbs

[Deltarider]

If it is a 74 it can only be a K as the 550 didn't come out until 75.

How are we supposed to know?

If the slow jet is actually clogging then you need to replace all your fuel lines including the ones that connect the 2 pairs of carbs

Nonsens. That could mean a lot of unnecessarily work. Slow jets can actually clog by residues of gas that have hardened (lighter fractions having evaporated) and rarely do so by dirt. The 2 pairs of carbs are not even connected, but each pair of carbs has its own fuelline. The fuellines from the tankpetcock to the T-joint that feeds 1+2 should be 18cm and the one to the T-joint of 3+4 should be 30cm. Ideal ⌀ 5,5mm. Guaranteed good flow because no kinking. Inline fuelfilters are to be abandoned. They do more harm than good.

[BomberMann650]

Amsoil Quickshot cleaner does handsfree cleanouts rather well.  It won't leave a massive cloud of smutz in the air and you won't have to wait overnight.

[RAFster122s]

Petcock can have debris issues or the tank.  Need to check the petcock screen and your tank for rust and debris and changing the fuel lines is a good idea on bikes new to you.  Honda oem fuel line is of thinner wall construction and will fit through the carb rack's openings.  Be careful with the T fittings between carbs, they have been broken before. 
The screen in the petcock fuel bowl can fail or fall apart on 74's oval petcock mounting a pair of screws to mount.

[Bankerdanny]

I meant the 2 carbs, not the 2 pairs.

How would we know what? He says he has a 74 550, there was no 74 550F, there was only a 550K.

People often don't replace the connector hoses when replacing the others because it's a pain in the ass. The clogging issues could be gunk from old gas in the carb itself,  it could also be rubber bits from the old bit between the 1 and 2 carb.