Carburetor rebuild

2015-07-02 23.02.44

Rebuilding carburetors a carburetor for the first time is a lot like having sex for the first time.  You pull off the cover and find a whole bunch of parts, tubes, and pieces that you’ve heard about before and maybe even seen some illustrations in textbooks, but the moment you start prodding around you instantly feel like you missed a step and you’re in way over your head, and that carburetor knows it.  All your friends are going to laugh at you when they find out you tried to stuff a secondary jet into the idle jet hole.  Compounding this difficulty is the fact that Honda used at least three different carburetors during the 4 production years of the CB/CL350, so online information is often incomplete and unclear.

 

2015-07-02 17.19.41

 

And oh yeah, it’s filthy down there.  Note how the old float bowl gasket is actually flattened and bonded to the groove of the float bowl.  This is the reason that gas was seeping out of the sides of the carburetors before I took them off of the bike.  2015-07-02 17.19.34

I used a set of K&L carburetor rebuild kits to rebuild my carburetors.  They contained the right replacement parts for the primary and secondary main jets (#68 and #105), needles, float bowl gaskets, and float valve assemblies.   I was afraid that I’d crack the ancient brass floats if I attempted to pop out the float hinge pivot, so I never got down to the float valves to replace them.  I really wanted to replace the slow jet from the left carb, but the kit had the wrong size jet included.

When you remove the three jets, you should be able to see straight through the primary/secondary holes to the throat of the carb (two larger holes on the left), but not through the slow jet hole.  This is because the slow jet feeds fuel through a passage that makes a turn towards the outlet side of the carb where it lets out just on the engine side of the throttle plate.  2015-07-02 23.02.57

 

So I didn’t get a chance to replace the slow jet or float valves, and because I didn’t detach the floats, I didn’t soak the carb body in carb cleaner.  I did set the float levels by eye.   I also pulled the slide and replace the needle.  In hindsight, it probably would have been a good idea to lubricate the slide with some WD40 or something as well.   I just didn’t think of it.

 

2015-07-02 23.12.44

There are three passages that connect to the area under the diaphragm.  I am not sure what these are for, and I did not clean them either.  I will likely have to do that in a future rebuild.

I painted the top covers because they were rusty and disgusting, and then reassembled the carbs.  I installed them on the bike and sync’ed the throttle cables.  The bike started right up.

I am finding that the bike has lost the problem it had before of holding revs after the throttle is closed (probably due to cable synch issues), and that power is greatly improved.  Tuning was still not possible however because the idle screw on the left carb doesn’t seem to have any impact on the idle speed of the bike.  I will probably have to tear that carb apart again and thoroughly clean the idle jet and/or idle screw.  Hmm.

Much like my first time having sex, I did pretty much what the books told me to do and conquered some of my fears in the process, but I ultimately left the job less than satisfactory and will need to do another job to really clean things up.

 

 

 

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