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Old Faithful Gets What She Deserves—New 350A Carbs Dipped and Clean

August 18, 2012

The New Carbs and Components Out of the Dip and All Clean

 

I was successful in obtaining a matched pair of 350A carburetors on eBay for $51. Here are the carburetors and associated bits and pieces after an overnight dip in Berryman's "Chem-Dip" and thorough blasts of air from the compressor to make sure that not only the fuel passages are clear, but also the air passages. (You can buy that gallon can of dip, and it comes with a strainer basket inside, at any auto parts store for less than $40.) The critical bits, such as the float needle tips and the seats were polished using a Q-tip and "NevrDull" wadding and a little StrongArm for lubricant. The diaphrams proved to be in good condition with no pinholes or tears. I was careful to keep the diaphrams well away from the carburetor cleaner.

 

The 350As are fairly rare as they were only used on the very early CB350s with the "hot rod" cam. My 350 is a very early bike and has the cam, but I discovered when I started working on it that someone had substituted a 3D carb for the right-side. Of course, getting the bike to run properly with a 350A on one side and a 3D on the other, both being jetted completely diffferently including the air jets), proved almost impossible. I ended up pulling the 350A from the left and replacing it with a salvaged 3D. 3Ds were all I could find at the time so I compromised and rejetted both to approximate as closely as possible the fuel settings of the original 350A carbs. This worked pretty well, but now with the matched set of 350As the bike's fuel system will be back to original.

 

The Rare 350A Carburetor. The carb model numbers can be found here and are often very faint.

 

For the first time working with these Keihin CV carbs I was able to get every last bit out of the bodies, including the jet nozzles, which sit just under the jets. It is critical to get these jets clean because the very tiny holes on the side of the bodies can be plugged very easily.

 

All the Jets, Nozzles, and Other Bits from inside the Carburetors.

 

The one set of nozzles I have never had any luck getting out of my other carbs were the nozzles in the left foreground in this picture. I was able to coax these out of both 350A carbs. Unfortunately, the one's screwdriver slot is broken. (The nozzle doesn't screw in; the slot is just to enable you to wiggle the nozzle back and forth to loosen it, after which you push it out from the venturi.) I at first thought I could pull one of the others out of the other carbs (I have several CV carbs) and replace it with one that still had a good slot, but after much work getting another whole one out without damaging it, I noticed that the 3Ds had extra lines of holes 90 degress to the ones on the 350As. They were not the same and not interchangeable, so I will resintall the less-than-perfect one I had taken out of the new 350A.

 

You can see here the broken screwdriver slot on the nozzle. This should not affect performance, so it will go back in.

 

Next, I will buy a new set of gakets and o-rings for both carbs and reassemble. My cousin has agreed to repaint the tank, fork covers, and side covers, so they will go out to him in Plymouth, Indiana, soon. I also have been reasearching rechromers and think I have found one near Miami (Thanks, Bob!). I need to call them and get an idea how much all that will cost, once I sort out what goes and what stays.

 

Cheers,

 

Road Dog

"Ride Your Own Ride"

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October 26, 2018

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