Easy idle mixture circuits clean.

ck_516

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I received a 1978 CB750K from a good friend of mine. It had sat for 19 years. 12K miles, looks like brand new.
I got everything OK, except the idle circuits. It was HARD to start and would not idle for anything.
So, I removed the fuel line from the tank petcock, drained the float bowls then closed
the drain screws..Used a very small metal funnel (Ebay) and placed it in the end of the fuel line
and filled the carbs with Sta-bil Green (marine) until the fuel line was full. I opened the idle mixture
screws to 4 full turns out. I let it sit for 48 hours. Then, I hit the starter with choke on and throttle closed to
create maximum vacuum. Did that 4 or 5 times for about 10 seconds each. Topped off the fuel line with
Sta-bil green. Let it sit another 48 hours. One more shot with the throttle closed and choke on.
Then drained the Sta-bil from the float bowls, reattached the fuel line to the petcock and turned on the go juice.
Reset mixture screws to 1.5 turns out each.
Hit the starter button and the engine started right up with a good idle. The accelerator pump even works, now.
Your mileage may vary. Hope this may help someone.
 

Steve 750

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re easy idle mixture circuits clean

I received a 1978 CB750K from a good friend of mine. It had sat for 19 years. 12K miles, looks like brand new.
I got everything OK, except the idle circuits. It was HARD to start and would not idle for anything.
So, I removed the fuel line from the tank petcock, drained the float bowls then closed
the drain screws..Used a very small metal funnel (Ebay) and placed it in the end of the fuel line
and filled the carbs with Sta-bil Green (marine) until the fuel line was full. I opened the idle mixture
screws to 4 full turns out. I let it sit for 48 hours. Then, I hit the starter with choke on and throttle closed to
create maximum vacuum. Did that 4 or 5 times for about 10 seconds each. Topped off the fuel line with
Sta-bil green. Let it sit another 48 hours. One more shot with the throttle closed and choke on.
Then drained the Sta-bil from the float bowls, reattached the fuel line to the petcock and turned on the go juice.
Reset mixture screws to 1.5 turns out each.
Hit the starter button and the engine started right up with a good idle. The accelerator pump even works, now.
Your mileage may vary. Hope this may help someone.


This idea is a real hit for you, your confidence and qualifications on this carb model is quite remarkable. Knowledge means a lot on these carbs. I have had to learn these carbs also. I found that installing a inline fuel filter means a lot for these carb models. I am in the process of vapor blasting a set of carbs for my 1978 Honda cb750k. From what I know about these carburetors float settings mean a lot, because these engines were set up to run lean and warm up is a big deal. Once these bikes are warmed up they perform well, but the idiots that decided that fuel with crap a hol was a good idea. They know very little about the subject. So remember keep your bike loaded with a good additive like Sta bil or Chevron Techrolene. I surely love my 78 750k very much and they are becoming very valuable because they were the last year of the SOHC engine, they were also the best looking 750 for the 10 years they were made. Enjoy this machine they will run well if you are devoted to doing the maintenance, be sure to ride with confidence and desire. But most of all drive defensive additude to safety and you will have years of enjoyment.

Thanks
Steve Colville
 
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