1979 Honda CB750K Idle Problem Sticky Throttle

[ross1zac]

I recently bought a CB750K, the person who sold it to me knew the bike hadn't run in a couple of years and thought the carbs may be the problem. I am mechanically inclined so I removed the carbs and installed a carb kit on the bike. The bike runs and idles great but when you give it throttle the rpm's stick at 4000. I have lubed the throttle cables and the mechanism on the carbs but it still sticks at the high rpm's (the throttle itself returns immediately, so i do not believe its the mechanism or the grip). I also found that if I choke the bike it will bring the idle back down. This leads me to assume its a vacuum problem. I do not see any cracks in the boots connecting the Carbs to the heads. I am out of ideas any help is greatly appreciated

[cbRider]

Try spraying starting fluid on the rubber carb connectors to the engine.
Also check that the choke returns completely to the off position.

[ross1zac]

I have tried that, there is no jump in the rpm's when i do it. The choke is returning completely also.

[cbRider]

ross1zac, the carbs are the most troublesome thing on those bikes until you get them set up right.
Make sure there is some slack in the cable when the throttle is closed.
Did you balance the carbs. The linkage between the carbs is also critical. Make sure the slides move up and down freely and the air box needs to be in place if you are using one.
When I work on mine I remove the gas tank, put it on a table or work bench near the bike and run a long piece of fuel line to the carbs so I have good oversight of what I am playing with.
I had to take mine off three times but now it purrs like a kitten. (I wonder how long)
Good luck and be patient, you'll get it right. Sometimes we overlook the little things.

Karl

[dylansdad022102]

about your bike getting stuck at 4k. its probably your vacuum slides are sticking on varnish or dirt. pull the tops off your carbs and clean your needle slides as well as the inner walls. lube with teflon spray or atf fluid. you will be suprised at how much better your throttle responce becomes.

[ross1zac]

The slides were cleaned with carb cleaner when carb kit was installed. The carbs are dirt and gum free.
I am really lost and have no idea what else to check. I did a spray test at all the boots and there was no change in my idle.