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cant get a steady idle

leo750k

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I am now getting ready to do the throttle drop procedure on my 1980 k model. Cant get a steady idle. Using the idle adjusting screw I can get it down to a fairly low rpm, and I think "that doesn't sound to bad" and then in about a min. or two, it starts surging up to over 3-4 k rpm. I adjust the throttle screw down to a decent rpm, and then in a min. or two it starts loosing rpm and dies. I seem to be stuck in a loop.
These are newly re-rebuilt carbs, and the first time I am attempting to to tune them since installation.
All advice is appreciated,
Thanks,
Leonard
 
Vacuum leak or sync issue. The leak shows at the rpm rising, then you artificially cut idle back for the leak which is not normal, then of course it dies, the throttle is then closed off too far.

One other thing...........if all that is occurring at cold engine warming up it is NORMAL. You only have a problem if the engine is doing all that at fully warmed up.

Explain what you mean by 'throttle drop', likely that is an error.
 
I was reading some of your responses in other posts, and am beginning to think I have never really had it completely warmed up. New to air cooled motors, have been scared to let it get to hot just sitting there. so how hot is too hot?
My mistake, it's "idle drop procedure" section 4-17, under pilot screw adjustment
Thanks for the help
 
I finally got it out for about a 20-30 min. ride today, temp here is 88 deg. so I know it got fully warmed up, and the idle was more consistent. But I could not get it to run over about 2k rpm, until I thought lets see what some choke will do? with the choke fully on I could get up to about 4.5k rpm. Then I stalled it at a stop sign, and realized that now my battery is dead too. push started it and rode home. looking into my charging right now, but i could still use some advice on the carbs.
 
Carbs will seem to give trouble until main power is correct, the engine won't rev low on volts.

Idle 'drop' is an emission thing to set lower emissions ONLY, you are looking for the best idle you can get, which means NO drop. Most end up at 1000-1200 rpm idle hot. The better shape the engine is in due to rings and valves the slower it will smoothly tick over at idle. Leaky valves make the engine more erratic at idle provided (the big one) the carbs are CLEAN, the number one problem with these since they are so complicated. I could write a 500 page book just on the pure idle to off-idle transfer these do, it is crazy the way Honda made those carbs.

Why I asked in particular about idle drop? Any drop doing that is lean, you want the mixture screws set slightly richer to best highest rpm at that idle speed setting. If speed is then too high lower it with main idle speed knob rather than leaning carbs out more, the idle will be much smoother that way. Use 2 or higher turns on the mixture screws, it lowers popping (pipe backfiring from too lean) at decel too.
 
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