!977 cb750k carbs

[hood624]

I have a 77 cb750k the bike runs good idling no problem except after riding it a week or two it will foul the plugs i know this means i am getting to much fuel but at the same time you can be riding and get on the gas and when you hit around close to 5000rpm it will cut out like someone cut the fuel off does this mean there so much gas that it is just not able to burn it or what i not sure what i need to do if i need to mess with the air fuel mixture or what any help would be good and the carbs are syni to the main #2 carb

[TOOLS1]

It does sound like a rich condition, but there are some questions. What color are the plugs? What type of exhaust? What type of air cleaner, and do you know what size jets you have?
TOOLS

[hood624]

the plugs are black from things i have read it say to run the bike at a constant speed then pull clutch in and shut the bike down and remove the plugs to check for the right plug color is that right or not i always been told not to pull plug in a aluminum head so you dont mess the treads up but it has pod air filters  and i going to tear it apart to find out hte jet size should it say what size it is or how do i know but another thing i noticed was in the top gear if i try to accelerate it wont just have to barley give it gas until it gets the motor turning fast enough  to get in a higher rpm

[Lucky 1]

Sounds like the idle jets are clogged.
Also have you checked the accelerator pump system and spray nozzle function?
If you are running pods and aftermarket exhaust and has not been re jetted then it will never run right.

I think this is way over your head.


You can pull plugs in an aluminum head but you should let the engine cool down a little first.
ALWAYS, ALWAYS start the spark plugs by HAND when putting them in.


Never use a rachet and socket to start the spark plug.

Do not worry about plug chops until you have done everything else, and it is very close to running right.
Then think about plug chops.


REmove the carbs.
Put in new float needles.
If they are all metal use a new seat and new needle.
Measure the floats exactly like the book shows you.

Remove the idle jets and use a #10 electric guitar string to clean the idle jets. Then use carb cleaner and compressed air. Look through them. Make sure you protect your eyes.

If you are using pods and aftermarket exhaust put in #42 idle jets.
Raise the slide needle by lowering the clip ONE notch.

Remove all 4 mixture screws and make sure the o ring is not damaged or distorted.
Put them back in and set all 4 ,one turn open. Make sure they all have a spring and washer.

Put in #120 main jets.

After you have the carbs on sync the idle on all of the carbs.

[hood624]

i got the carbs pulled today the accelerator pump is working its putting fuel through all four carbs and checked the main jet and it has #110 in all four and it has #35 for idle jets do you think that putting in the 120 main jets and 42 idle jets will fix my problem or what i new to this and i appreciate all the help i can get

[hood624]

the elevation where i live is 1500ft

[hood624]

i got my jets in and for some reason they sent me the wrong slow idle jet they sent me a jet of size 30 jets and 120 high speed the bike will not run properly like this right there would be to big a jump in jets i new to the hole  jetting carbs any help will be grateful  

[Lucky 1]

You will need those #42 idle jets with pods and aftermarket exhaust.
You will need to raise the slide needles by LOWERING the clip one notch.
Put in those #120 main jets. Good insurance against lean condition at WOT.
Mixture screws open 1 turn.
Make sure those mixture screws have the washer ,spring,
and O ring. Make sure the O ring is in good condition.

[Lucky 1]

#30 idle jet will never work. Send them back.
Someone needs new glasses.

[hood624]

yea sucks to have to wait another week to get them but what can you and i dont think the needle has the clips in the 77 cb750k its a washer made on it from what it looks like

[hood624]

how do i raise the needle on the 77 there a fixed has no adjustment like other casrbs i have seen

[Lucky 1]

Does the needle just have one clip on the needle?

If so you have two choices.
One choice is to put washers/shims on the needle to raise the needle.
The other choice is to find some 1976 or 1977 needles that ARE adjustable.

IF you go with the shims you will need vernier calipers to accurately measure them.
If you add one .020-,.022 thousandths shim and it sits on top of the pocket in the bottom of the slide,
that pocket is .012 thousandths deep so it will raise the needle a total of .032+ or - and that is qbout 1/32
of an inch. PErfect.

IF the shim/washer sits down inside the pocket in the bottom of the slide then you will need to have two shims that equal .032 thousandths. Make sure the shim does not get stuck in the needle holder.

But you have to raise that needle if it has pods or stacks and aftermarket exhaust.
Otherwise the throttle response will be very poor when giving it quick throttle.

[Lucky 1]

That is because it is too lean in the midrange.
So by the time the needle is raised up high enough, THEN it can be using most of the main jet.

[Lucky 1]

That is because the 1977-78 models were these EPA models, but the new non adjustable needle may
not have been changed or a previous owner took it.

[Lucky 1]

Did you actually see the gas squirt out of the brass nozzle in the intake of the carb???

[hood624]

yes took the intake off and made sure that the accelerator pump was pushing fluid out of all four of the carbs but here is my problem i bought the carbs online and they had been rebuild and chromed out very nice and its almost like the accelerator pump loses its prime after it has been sitting for an hour or so therefore is the tab that moves the stem of the accelerator pump supposed to be touching

[hood624]

Is this what i need to buy

http://www.ebay.com/itm/1977-HONDA-CB750-CB-750-CB750K-KEIHIN-CARB-CARBURETOR-JET-NEEDLE-F2051E-/290937712671?pt=Motorcycles_Parts_Accessories&hash=item43bd3d301f&vxp=mtr

[hood624]

the ones in the bike say 15A

[hood624]

got everything in today and i set the needle at the middle setting i got the air screw at 1 turn out and it  got black smoke coming out of the pipe do i need to set the clip down one or what on the needle

[TOOLS1]

What RPM is the engine running when the black smoke is coming out?
TOOLS