Sunday, May 27, 2007

Carb Rebuild

Picked up two carb kits for $25 each, and the correct main jets for another $6 each, for a total of $31 per carb. Now, instead of topping out at fifty-five, I'm shifting into fifth at fifty. She makes sixty at just about 5900 rpm, seventy at about 7k. Acceleration is better too. Hot damn.

Right Carb

The rebuild kit for one carb. Had to buy a separate main jet as the one in the kit was 115, and I needed 105. Not that I would've known that, but Charlie hooked me up.

Disconnect the air filter, throttle cable, and choke linkage. Remove the carb, stuff a shop towel in the intake to keep anything from getting in.

Removing the diaphragm/slide assembly (after removing the top cover and diaphragm return spring).

Removing the float bowl.

A view of the float bowl, floats, jets.

Removing the primary and secondary main jets and the holder. Just pull on them with your fingers.

Main jet holder, needle jet, primary and secondary main jets. To remove the main jet holder and the needle jet which are under the primary and secondary main jets, you reach down through where the diaphragm/slide assembly was and press them out with your finger or a toothpick.

After removing the above.

Pressing the float assembly pivot pin out with a toothpick.

Removing the float needle.

Unscrewing the float valve seat retainer clip.

Not shown: remove the float valve seat by grabbing it with needle nose pliers. I used a shop towel to protect it from the pliers. Then remove the 'pilot jet' which turned out to be just a little rubber plug. Under that was the slow jet which just unscrews. I don't know why Clymer's says to push out those two, because there's no pushing involved. Also remove the idle mixture screw and spring, and the float bowl drain plug. Then use a pair of needle nose pliers to reach down inside the diaphragm/slide assembly and compress the retaining clip. Just grab one side and pull in inwards instead of trying to grab both at once. Remove the clip, the little plastic piece, and the jet needle. Hit everything with carb cleaner and compressed air. Make sure to spray through all the little holes and passageways in the jets and carb body. Carb cleaner is nasty stuff, so if you don't have goggles use the safety squint.

Cleaned up, in the process of being reassembled.

Measuring the float height.

Pilot jet.

From top left: needle jet retaining clip, a silver thing and washer that I didn't end up using, main jet holder, primary main jet, o-ring, needle jet, secondary main jet.

The jets before pushing them in.

The hard part is over.

Jet needle retaining clip after bending it to match the old one below it, plastic thingy, jet needle.

Reassembled diaphragm/slide assembly.

View inside the diaphragm/assembly. You can see the plastic thingy and retaining clip.

Float bowl and new gasket. Didn't bother with sealer.

Putting the diaphragm return spring in after putting in the diaphragm/slide assembly.

Nice clean carb back on the bike. It did leak gas through the overflow at first, but hammering on the float bowl with a screwdriver managed to unstick the float.

Left Carb

A view inside of the main jet holder and the needle jet poking up. They're to the left of the butterfly valve in this shot.

Inside the float bowl. Note which side/hole of the primary and secondary main jets is facing out.

Cleaned and reassembled.


  1. Hey Darth.

    I'm glad I found this. I just rebuilt my carbs (72 cb350.) I believe the carbs are identical to yours. I used the same kit, and couldn't find a place for the "little silver thing and washer" either.

    I didn't use a manual, I just tried to figure it out. Now I have a leaky carb on the right side. I suspect it's the gasket because when I saw the gaskets that came with it, I assumed they gave me the wrong ones, because they were round, and not the pentagon shape of the float bowl.

    Was I supposed to just force the circular gasket to conform to the pentagon shape?

    I ended up using my old gaskets that were in it, because they were the right shape, although they both were torn.

    I appreciate any help you could give me.


  2. Nice writeup, Thanks for the info!

  3. Great job! Thanks for the help. Just completed a successful carb rebuild.

  4. Well done I do lots of these but you did a nice job.

  5. That`s great man. I have 1968 cb 350, but i dont have the original carbs. Im looking for that carbs. Anyone can help me??



  6. Thanks for the detailed pictures, this will surely help when I tackle my carbs. Charlie's Place did all the maintenance on my bike for the previous owner of my bike and I have the same air filters on my bike. Have you found that this effects your air-fuel ratio? and did you have to adjust your carbs because of this? My bike would only run w/ choke on so I decided to clean carbs... but i thought it might also have something to do w/ the air filters throwing everything out of whack...

  7. Need carburetor help! Trying to clean a carburetor on 1970 Honda CB350. Having trouble getting what I think is called the "Needle Jet". I just can't get it to come out. I'm worried that I'm going to damage it if I fiddle around with it too much trying to force it out with needle-nose pliers. I sprayed carb cleaner on it and left overnight, but it's not budging. Any advice? Can I just bang it out and go buy a new needle jet to replace it with? Do they sell them individually or do I need to buy a whole kit? All other parts are in workable condition. Thanks!

  8. where do you buy the o rings....Honda prices take your breath away.... John

  9. What air filters did you put on that? I have a 73 and want to do the same switch.

  10. Dude. You're Awesome. Thanks for posting this.

  11. Hello Great post, I recently "restored" a 1973 cb350. Today on the way into work, i was going about 55mph, and out of the blue, just started to loose power, I'm thinking the carbs need to be cleaned or its running too rich from the new pod air filters similar to your i also have installed.

  12. Hello just picked up a 1970 cb350 my carbs might be bad because it drops fuel out the bottom of the bowls. thought it was the floats stuck, had someone check them. any recomendations? Nice bike btw looks clean!!!!!