Honda CB750F -83 bad idle

Hi Group!

My Honda cb750f -83 idle dies after running about 1 minute. It fades
down and if I give a little throttle it goes up and fades again .. or
it goes up and stays up (over 2000rpm and increasing). Do you have
similar experience with your Honda and what was the reason or
correction for that problem? I've syncronized and cleaned the carbs
(but anyway it seems that 4th cylinder runs too rich). Is this
carburattor problem at all -or is it some elecricity related thing?
This problem occurs with both cold and warm engine. Any suggestions
please!

br, Jani

 

You may have a problem with a sticky float in that one carb and the
idle mixture is probably too rich. I've posted what to do hundreds of
times, but there's always a newbie asking the same question without
googling for an answer...

Look for "kaybearjr@aol +idle jet +EPA anti-tamper plugs"

All the Japanese motorcycles are generic, there are only two carburetor
manufacturer's supplying carbs to all the Japanese bikes, and both
manufacturers use jets that are almost exactly the same size. Those
Japanese bikes are appliances, you see one, you've seen them all. So
you don't need advice about some mysterious problem that only happened
to silver 1983 Honda CB-750's in a certain serial number range, you
need to understand how carburetors on Japanese bikes work and why it's
so important to keep the fuel system and the idle jets perfectly
clean...

If you understood the ignition system of your bike, you'd know that the
#1 and #4 spark plugs fire at the same time. One spark is at the right
time, it's on the cylinder coming up to fire on the compression stroke,
the other spark is a waste spark firing on the opposite cylinder's
exhaust stroke. If you had an electrical problem, it would appear on
*both* #1 and #4 cylinders, not just the one cylinder. And, electrical
problems will probably *never* make the engine RPM faster on a bike
with carburetors...

You probably didn't clean the critical port that is controlled by the
idle mixture screw. You can't get to this screw unless you drill out
the EPA anti-tamper plug. I've described how to do that about 100
times...

Dirty idle jets make the engine run too fast when you start it up,
because the mixture is too rich. The mixture from the idle jets plus
the mixture from the starting enrichenement valve have to be just right
or the engine will race up to 5K or 6K RPM with full choke on....

Then the engine will seem to be OK until it warms up and gets hot, and
the RPM will be too high, so you turn it down when you stop, and the
next time you start the engine from cold it idles too low, so you set
it back up again and you wonder why the carburetors are so
cantankerous, but you never bother to read up on how CV carburetors on
Japanese bikes work...

I've explained how CV carbs work at least 100 times, but somebody
always comes into the NG without doing any googling for CV carbs...

Try googling for "kaybearjr +CV carbs"