CB500 K carbs (Fouled plugs)

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Hi from Canada,

I have gas leaking from the air box. What can I do????

First, carbs were cleaned and set to original specs, installed a MAC muffler 4-1, original coils, new spark plugs D7EA, new battery, main jet are 110. It starts up pretty well but very rich. It'll only start with the choke wide open.

My questions are:

What can i do to adjust the carbs so it run leaner? How do i move the needles? How do i bench-synched them with the drill bit method.

Any help would be greatly appreciated.

Dan from Canada

-- Dan Savage (ds2624@hotmail.com), May 07, 2002


Hi Dan,

no time for a lot of rambling so here's what i have to add:

- my 76 cb550 has got K & N individual filters and a CB650 4 into 1 exhaust system (MAC i think)

- with the original 100 main jets it ran quite rich - yeuch!

- i changed to the next size down - 98's. only $5 each from Honda including a new o-ring. a good deal i thought.

- bike starts and runs fine now, though i haven't dared to look at the plugs yet. i still get a bit of black smoke when i rev it, but the smell of a rich engine is not so easy to detect now.

what part of canada are you in? i'm in vancouver.

bye, mark

-- Mark Robbins (arialex9@hotmail.com), May 31, 2002.

You can adjust the main needle setting so the main needle sits lower in the main jet. Start by removing the slides from the top, removing the bracket from the slides, and withdrawing the needle from the slide. The needle is held at its height by an 'e' clip. If you move the clip to a higher notch, that will lower the needle and reduce the flow of gas throughout the range. I would recommend going with a smaller jet, because a 110 is awfully large, even for the MAC muffler. Try a 105 and see how that works, adjust the needle to fine-tune the jet. Nick

-- Nick Lenarz (n9viw@yahoo.com), August 13, 2002.

Hi Dan, Sorry for the late response, but I just found this forum. Several years ago I bought a 77 CB550K that had been sitting for four years with gas in the carbs. The gas had totally evaporated and the residue had formed fairly large cristals in the float bowls. The first thing I did was clean the carbs (I thought). The bowls would fill and not leak but the bike would only run on full choke, and very rich with lots of black smoke. As soon as I let off the choke the bike would die. So, the idle circuit was not working and the full choke was forcing the engine to suck gas up through the main jet. I had removed the mixture screw, spring, and "O" rings (mine also has tiny rubber "O" rings at the base of each mixture screw, applied a xylene/toluene carb cleaning mixture to all of the idle circuit passages and blown the passages out with compressed air. The beast would still not idle. My pilot jets were still plugged. I could tell because when I used a piece of vacumn tubing to blow air with my mouth through the pilot jets they were plugged (I could hear no air going through). Although every manual ever written says to never use a wire to clean jets I used the high E string from an extra light set of guitar strings to clean the pilot jets. This is the only wire I have found small enough to go through these jets. The string size is .008 and a full set can be purchased for about $4 from any music store. After I removed the blockages in the pilot jets (the smaller tube that extends down into the float bowl in front of the main jet) and again blew out the entire circuit the bike starts very easily and idles beautifully. Good luck!


-- Junkman Frankenbiker (everett@on.aibn.com), September 21, 2002.

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