Topic: Should CB750K4 carbs have brass or solid plastic floats?

[Holden]

My '74 CB740 K4 has carbs with plastic floats.  I want to make sure these are stock so that the stock float heights spec applies.  When did Honda switch from brass to plastic floats?

Thanks.

[Johnie]

The K4 is plastic. My K1 had the brass so I guess the plastic came in after that sometime.

[Holden]

Thanks for the info!

[Johnie]

The old brass are leak prone. Plastic hold up better.

[HondaMan]

My '74 CB740 K4 has carbs with plastic floats.  I want to make sure these are stock so that the stock float heights spec applies.  When did Honda switch from brass to plastic floats?

Thanks.

The plastic ones were phased in by the New Factory on the latest K1 bikes. By the 3rd month of K2 production, all were plastic. The brass have one slight advantage when racing: their weight and bouyancy is such that they let the float bowl run a little deeper, as if the plastic ones were set at 24mm instead of 26mm. This improves WOT performance a little bit, but makes the bikes tend to leak from the float bowl gaskets when on the sidestand with the petcock on.