Topic: 72 CB500 initial carb settings

[Goofaroo]

I am combining parts from two sets of carbs to make one nice set of 627B carbs. I am finally done cleaning and sorting and ready to begin reassembly. I have looked at the manual on the home page and this site  http://www.motorcycleproject.com/motorcycle/text/specs.html  and I get a bit different information. In addition, I have some slight mods to account for. I would appreciate any advice to get me very close to correct first try.

I will be running a Mac 4-1 exhaust and will possibly shorten the baffle a bit.
Factory air box with a foam Uni filter. I am missing the air box cover right now but hope to find one. All other specs as far as timing, valve adjustment, etc. will be set to stock. The only other change I may make once I get it running is Hondaman's ignition mod.

The specs that I have found show 100 mains, 40 slow jets, 22mm float height, 4 on the needle. Does the 4 mean 4th groove from the top?

I have both 100 and 110 mains available. I live at 1300 ft so factory sea level settings generally apply. I know that on most modern bikes I have owned they have generally come lean from the factory for emissions reasons but I'm not sure if that rule applies to a 72 model. Any advice that might save me from dismantling these again would be greatly appreciated.

My best guess would be to install the 110 mains, and cross all fingers and toes. This guess is based solely on the change from the stock exhaust and air filter.

[Deltarider]

I know that on most modern bikes I have owned they have generally come lean from the factory for emissions reasons but I'm not sure if that rule applies to a 72 model.

Certainly not to a 72 model. I'd start with #100.
My 500 [ED] originally has #78 main jets and still is on the rich side at WOT. Originally ours had the needleclip in 3rd groove.

[Goofaroo]

Thanx for the reply Deltarider. From what I've been able to find out you have the 649 carbs which weren't available to us here in the states. I have gotten no other response but I'm snowed in today so I thought I'd start reassembly. Unless I hear otherwise, I'm going with the 100 mains, 40 slow, and needle clip in the fourth groove from the top. Any opinions on the needle position would be well received since it is such a pain to remove these slides once the carbs are installed.
Anyway, my new question is about the slow jets. The picture below shows the two versions that I have removed from my two sets of carbs. Obviously they are completely different although both are #40s. Any comments or suggestions? I'm guessing that the one on the left (longer one) is the factory part and the other is from an aftermarket kit. I am planning to clean and install the ones on the left unless I hear otherwise but some reassurance would be welcomed.

[Deltarider]

The one on the left is the original. Check if it's clean. You should be able to see through it, but the hole is very small indeed (0,4 mm). You can leave it overnight in some carb cleaner. Carefull with cleaning, the hole is easily widened. So, use a copper strand wire.
The carb settings in the American Honda Company booklet confuse me and are certainly not known here.  

[Goofaroo]

I kind of figured they were so I cleaned them up along with a few other brass pieces. I've had this K&L jet cleaning kit for at least 20 years and it has been invaluable.

I've been surprised that not only can I not find any decent info in the Honda manuals but nobody on the site has chimed in. I figured putting a Mac exhaust on a CB500 and running the stock airbox had been done before.

I'm thinking about using the 110 mains since I have replaced the paper filter with foam and will be running the Mac pipe. They are also factory jets and the set of 100s I have are aftermarket. Not a big deal to change them later if I need to. I am however really hoping that my needle clip position is correct. I have plenty of other things to do to this bike without having to completely dismantle the carbs again to change the needle position.

[Scott S]

   Start with the 100. I'm running the exact same set-up as you: CB500, Mac 4-1 and Uni Filter in the stock air box.
  Needle on the 4th setting. Runs great.
  The stock slow jets (the bigger one of the two pictured) solved a TON of carb tuning issues I had. Just set everything up as you described, bench synch them and give it a shot.