Cb550 Carb Issues

[rcollins09]

Hey guys, I very rarely post just troll in the backgrounds and soak up knowledge and pervious experiences from people. Im just about done renewing my fuel system on my 76 cb550f super sport. The gas tank liner started flaking apart and rust was clogging my lines, filter, so on. So i cleaned the tank, relined and painted it. Did new fuel lines filter and so on. I also took the carbs off and saw they were a little dirty. So I completely dismantled them down to every little bolt. Cleaned them and am putting them back together. Don't worry I know what Im doing putting them back together. My question is as I am rebuilding them Im going to add a 4-1 exhaust and pod filters or velocity stacks, haven't decided for sure. But I need to know what actions to take to tune them. My stock jets are 100 (Main) and 38 (Slow), After some research I figured out I would need a 110 (Main) and 42 (Slow). Is there anything else I need to do to tune them? I hear people talking about shims and I don't really understand what they are shimming? The needle that goes through the center of the slide? To raise it up more? I also saw the notches on the c-clip on that needle and left them where they were on the second to highest notch. Do I change the location of that also? I have the carb Sync gauges once they are back together along with a float height tool. I just need to figure out how to set them up for the new setup.

Sorry for writting a book, just wanted to get all the details out there so whoever helps me has the right info.

Thanks,

Ryan

 

[forcefanajd]

As far as my experience with cb550's goes, I had a 550f with velocity stacks and an open header and I didn't have to rejet, just dropped the clips for the needles one notch, bench synced them, vacuum gauge synced them and I was able to dial them in no problem. FYI, I was concerned about the same thing during my project and that thing ran like a raped ape.

 

[forcefanajd]

Keep in mind the bike had a header when I got it so it may have been rejetted before I got it (I can't recall) but I don't think it was

 

[rcollins09]

How do you determine if you need to move the clip on the needle? and what exactly does that do. I know it moves it higher or lower into the float bowl….so that lets it get more fuel if its lower in the bowl?

 

[forcefanajd]

(l)ower the needle = lean )(r)aise the needle = rich

needle position is just used for the mid throttle range, i was just telling you what i had to do to get mine dialed in. (i tuned mine wit a wideband o2 sensor and it took all of 20 minutes to pretty much figure out what i needed to do to get it dialed in)

make sure you bench sync them before you do anything.

 

[d9canada]

+1 to previous info, especially bench sync is all important. Start with the settings you had and go from there. You will know if it's flooding or too lean by the way it runs and by checking the plugs if you don't have a sensor.

Remember too that it's important to ensure your valves are set perfectly first or doing the dynamic sync is useless. One other thing, I hope that tank had the filter screen removed before you coated it? Make sure you use an external inline filter and ensure you have good flow out of the line with the petcock set to either 'on' or 'reserve' before connecting to the carbs. Sometimes, even when all is OK with the tank, you can get an air lock in the line.