Topic: Idle Jet Sizes #42 or #45 or something else?

[neurotoxin312]

I notice that my 76' CB550 bogs down when accelerating up until about 3000 rpms, then its hauls ass. I was told to increase the size of my idle jets by a mechanic. I am currently running K&N pods and a Mac 4-1 exhaust. I've been having a hard time trying to understand the meaning of the jet size numbers. I believe (not 100% sure) that I have a stock #42 jets on my carbs, I purchased #45 jets over the weekend in hops of making my mixture a little more rich. My question is if a #45 jet is larger than a #42? and Could this actually solve my problem of bogging down in the beginning or is this to much of a jump in jet sizes?

[flybox1]

those numbers are hundredths of a millimeter.
.42mm,  .45mm, etc.

im not 100% sure that your mechanic knows what he's talking about 
what do your plug deposits look like on a clean set of plugs after a short idle?
when was the last time YOU cleaned your carbs?
did you pull and inspect each jet for a number, and if it was clogged?
is your emulsion tube clean and clear?
stock exhaust? stock airbox/filter?

[neurotoxin312]

cleaned my carbs very recently with compressed air although I did not pull and clean the slow jets (I should have). I do not have a stock exhaust, its a MAC 4-1 and running K&N pods.

From what I hear usually installing pods mean that you have to have a richer mixture both Idle and Main jets?

[flybox1]

typically, yes, you'll need to go richer, but will you get the right result if your pilot jets are clogged? 

[neurotoxin312]

True. But I soaked the carb in carb cleaner and blew out every orifice with compressed air. I'm sure I should have gotten any gunk if it was there. Also, according to the PO the carb was rebuilt last year.

Do stock 76' CB550 come with #40 idle jet stock? Perhaps #45 would be a little too rich.

[Stoli]

Start with the 5th posting in the following thread and go from there:

http://forums.sohc4.net/index.php?topic=103861.0

[flybox1]

True. But I soaked the carb in carb cleaner and blew out every orifice with compressed air. I'm sure I should have gotten any gunk if it was there. Also, according to the PO the carb was rebuilt last year.

Do stock 76' CB550 come with #40 idle jet stock? Perhaps #45 would be a little too rich.

your choice, but i'd want to be sure my off-idle boggy condition wasnt just a crap clogged pilot jet, or a poorly set mixture screw.

[neurotoxin312]

How do I set the mixture screw properly?

[flybox1]

well, there is a stock setting, but you are far from stock, so, and IIRC, the mixture screw controls air on 550 carbs, you'll have to start from there, and adjust it based on how a new set of plugs look after a short idle under a fan. 
let your plugs be your guide.
if plug insulators are white, turn the screw IN to make the mixture richer.
if the plugs are black, turn the screws OUT to make it leaner.
make only 1/4 turn adjustments until you get it.

Might be a good idea to download the shop manual from this forum, if you havent done so.  Links are in the FAQ section