® CB350F myths, quirks and tips

  • Myth: The CB350F is jetted rich from the factory and either the float level must be leaned or the jetting. Not so. This fallacy is perpetuated on forums, so beware. Even after 5,000 foot elevation, the engine is rich by only one main jet size, requiring a change from a #75 to a #72 main jet.

  • Tip: It is well known by now that the Cruzin' Image big bore kit for the CB350F has a piston ring problem. The rings are soft, and if the installation itself (through improper machining) doesn't result in the engine burning oil, the rings wearing excessively by within just a few hundred miles probably will.

  • Tip: There is richness potential in the carburetors' needle jet and jet needle. These are high-wear parts and meter most of the fuel delivery. Thus many CB350F carbs being fifty years old and with some attendant mileage are operating rich and there is no solution because Honda is out of these parts.

  • Quirk: Like all of Honda's 70s fours the CB350F has an aggravating 180 degree throttle.

  • Tip: This however is easy to fix and yields a welcome benefit.

  • Quirk: The CB350F intake manifolds are not all the same. The center two are different from the outer two.

  • Quirk: These carburetors are prone to corrosion more than any other Honda carburetor, with the damage occuring mainly at the main jet tower. This is critical because the main jet must seal at the end of the tower, and when it does not, this is another potential source of operational richness.

  • Quirk: A good quirk this time. The CB350F is blessed with the only fast idle mechanism of the 70s fours, if you don't count the CB650.

  • Quirk: The o-ring that seals the main jet on this carburetor is not available from Honda or from any of the usual sources. Or any source for that matter save one, a company that sells only to shops and not to the public. It makes a difference.

  • Tip: It is ridiculously easy to stop front brake squeal on this model. But it is not done in any of the ways that folks talk about.

  • Quirk: These engines typically have very low cylinder compression due to defective valves with as little as 8,000 miles. This is not difficult to fix however and even to prevent. But until it is done don't expect good performance.

  • Tip: Too much is made of the typical Honda voltage drop of 2 volts at the ignition coil, with the addition of relays advocated to overcome this and supposedly improve ignition performance. Maintain the ignition system properly, service the harness connectors, adjust and service it skillfully, and do the same with the carburetors (the parts most affected by the drop), and you can ignore the quite normal 2v drop.

Last updated June 2023
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