Topic: 1978 cb750 needle valve question.

[Snider1970]

I have a '78 cb750.  Carbs 1&2 leaking like a seive but 3&4 are dry as a bone.   I did a clear tube test. 1&2 just keeps going up.  3&4 have nothing.  Removing the bowls confirmed it.  Checked the floats and everything looks right.  The are all set the same and open and close freely. 
That being said, if I am having float needle issues on 1&2 could that prevent 3&4 from getting fuel?.

[HondaMan]

I have a '78 cb750.  Carbs 1&2 leaking like a seive but 3&4 are dry as a bone.   I did a clear tube test. 1&2 just keeps going up.  3&4 have nothing.  Removing the bowls confirmed it.  Checked the floats and everything looks right.  The are all set the same and open and close freely. 
That being said, if I am having float needle issues on 1&2 could that prevent 3&4 from getting fuel?.

Up to a point, yes: the 1-2 side fills first on those PD carbs, due to the slight hydraulic advantage they have from the single-tube filling method that was used on those.
Once you get the 1-2 side to fill up and stop sucking up all the gas, then you'll get to work on the 3-4 side! Think of it as on-the-job training?

[madmtnmotors]

Cheap float needles will behave that way. Honda float needles work best, K&L float needles are a close second. I've had el-cheapo aftermarket rubber tipped float needles fail in less than a week. The alcohol laced fuels turn substandard rubber to goo...

[newday777]

I have a '78 cb750.  Carbs 1&2 leaking like a seive but 3&4 are dry as a bone.   I did a clear tube test. 1&2 just keeps going up.  3&4 have nothing.  Removing the bowls confirmed it.  Checked the floats and everything looks right.  The are all set the same and open and close freely. 
That being said, if I am having float needle issues on 1&2 could that prevent 3&4 from getting fuel?.

Welcome to the forum Snider1970
Did you get this leaking straightened out?
What float valves are you using in your carbs?
Have you cleaned your carbs with an ultrasonic cleaner and made sure the fuel ports are all clean inside the carbs?
Did you bench test the carbs on a rack(make one from 2x4s) and use a aux testing fuel tank before mounting them on the bike insuring they aren't leaking and have proper fuel flow to each bowl and level?
Are you using the stock PD42 carbs?

I've been reading through all of your posts and noticed that you haven't been doing follow up replying back to some of your posts topics you've started. Leaving them open unfinished like that doesn't help others that read them looking for answers to their questions when they find them using a search. Be sure that you complete your threads with your findings and fixs you do to get your bike running. It is how forums work for everyone. I'm not trying to give you a hard time, just trying to help you learn and grow through your project.