Topic: 77-78 cb750K carb differences and parts interchangeability

[timdhawk]

So i have a set from both years. One is all prettied up and ready to go, the other not so much. Other than the return spring and stock jetting differences, I am wondering, as an example, if the slide from one can be used in the other. There are some subtle differences such as weight (material?) and one is chrome lined and the other is not. They are the same diameter. More specifically can the adjustable needle (and/or the slide) from the 77 be substituted into the 78 for more tuning ability since the needle on the 78 is fixed? Or, are the subtle differences enough to make the carbs light years apart?
Thanks.

[Johnny5]

I thought the only difference in these two carbs are that the needles have notches on the 77 and the 78 doesnt.

[timdhawk]

I thought the only difference in these two carbs are that the needles have notches on the 77 and the 78 doesnt.

That is true. There are others like the ones i mention above, like the slide weight and material, return spring, etc..
My biggest wonder was is if the needles could be swapped from the 77 to the 78 and if that would help the tunability of the 78. I hear other years discussed where moving the clip on the needle helps tune the carbs but the 78 is SOL without the movable clip.

[dtmmil]

You can swap just the needle, or you can swap the whole slide over. I have done both and had good luck. The slides your talking about are a composite type slide, I don't believe all the 77s had them, some were chrome, some were composite. I had 78 carbs, I removed the return spring and put the 77 spring and arm on so I could run a different spring on mine, I run a single cable throttle so its just a pull and no push.