1978 Honda CB 750K rejetting the carbs

[billy]

is there an amp.sequence for the tree fuses  on my 78k? anyone know  i'm loosen battery power after  30 40 miles.

[TOOLS1]

Your bike is not charging.
TOOLS

[skrivan]

i was hoping to re-start this thread relating to re-jetting....what is the process?  pull carbs off, change the jet, see if it's better?  if not enough improvement pull it off again and go up another size (or back to original)?

also---is the 'pilot adjustment' performed while the bike is running and done with a short screwdriver and really small hands?  i assume the 4 screws under the carb are the pilots.  is this the fuel mixture?  i really only see the 4 screws under the carb and the bigger throttle stop screw.  thanks experts.

[cdaiscool]

Im dealing with those pilot screws right now. You run the bike, adjust to the target rpm, then adjust or down a little bit until rims change a little. Then use big screw to go back to target rpm, and repeat. Do this for all 4 carbs.

Then after that, you have to sync them using a vacuum gauge.

As for rejetting, you just put the new jets in and hope its good. Do this until you find a good match.

[skrivan]

so.......no science?  i like that.  just go until until it feels good.  that synch thing is harder without the tool.  i might end up buying/making one but that does seem like something i'll use once and then hang on the wall.

[skrivan]

so.......no science?  i like that.  just go until until it feels good.  that synch thing is harder without the tool.  i might end up buying/making one but that does seem like something i'll use once and then hang on the wall.

[cdaiscool]

Its rudimentary at best. I wouldn't say its too great of a way to tune something.

[Lucky 1]

Actually he was just telling you what he thought.
Is was very good advice. Free.

There is no re jet kit for the 1978 CB750. Mostly for later model vacuum operated carbs.
There are jet "kits" but you pay mostly for the dynojet dyno run certificate worth $100.
But if you do get a dyno test and any adjustments need to be done it can cost up to $300.00

You will not get those pods to work right unless you get some 1977
carb slide needles.

My suggestion is this.
Pods.
exhausts?
idle jet #42.
Mainjet #120
Needles one step up from stock (Compare the 1978 and 1977 needle to determine position)
mixture screws 3/4 turn open

There is another forum member working on this problem now,(Brewesky)
except he has a stock airbox with 4 one inch holes drilled in it.

The stock airbox only had 3.7 square inches of intake area.
The airbox was like a giant choke.
The carb openings added up to 10.67 sq. inches of intake.
So only about 30%of the air.

The pilot air screws are now called mixture screws. they do the same thing except one controls the air by moving the slide up or down and the "mixture screw" controls the fuel by limiting vacuum over the idle jet.
That is what the little holes are for in the push in style idle jet.

Make sure all 4 mixture screws are the same amount as close as possible.

The very last step is syncing the carbs and then you do not adjust the mixture screws.
You remove the top of carbs #1,#3,and #4. Use a 8mm wrench to loosen the locknut controlling the up and down movement of the carb slide. Vacuum should be about 10-12Mg vacuum.
#2 is non adjustable. That is the "master carb." IT has the accelerator pump.

[Lucky 1]

Best solution is to get some CR racing carbs that ARE fully adjustable... About $700.00