Why is my bike running at full throttle?

[tris27]

I just rebuilt my carbs and put electronic ignition on my 1973 cb750.  I just fired it up and it is running @ 6000 rpms on idle and leaking gas from the overflow tubes on carbs 1 and 3.  Any ideas on what I might have missed or screwed up putting the bike back together?  Thanks,

tris

[Pretzel-2]

What height did you set the floats? Did you bench sync the carbs with a paper clip? It sounds like 1 and 3 are overflowing do to incorrect float height or sometimes the bowl gasket can squish out and cause the float to stick, Did you replace the float seats? The high idle is because your slides are too high, pull them off and check them from the motor side, insert a paperclip and lock them all down. Put them back on the bike and use the the big thumb screw to back them down to 800rpm or so. make sure the idle screws are 1.5 turns out and see how that runs.

[Firehawk46064]

zip on over to www.hondachopper.com ... they can help ya!
(specialize in the older cb750 K SOHC model bike)

[John B]

You say that you rebuilt the carbs. Did you replace the needles and jets? Sounds like 2 of them are stuck, or the floats on 2 carbs are hanging up. Did you take the carbs off the rack? if so I think that  you'll need to sync the carbs. Set the idle back with the set screw on the top of the rack.  I've been going thru the same mess with a '74 CB 750 that I've had for 30 years.

John B

[rm56-2]

Yes I agree with pretzels logic, Two of your floats are not set right. Either the tang is not closing the main fuel needle and your bowls are overflowing out the tubes. Or your main fuel needles are sticking open. You did set the float levels at 23mm right? Also as he said screw in your idle speed screws all the way in and back them out 1 1/2 turns, that a good starting point. Lastly with your air filters off check to make sure the carb slides are closing all the way. And make sure you put the slide in aligned with the notch on the slide and the pin in the carb body. Check the throttle cables and return springs for correct "feel". 6000 rpm wow, hope you shut it down quick?

rm