High engine revs on start up

[CBX1000_imp]

I have some ideas, but first I’d like to do some battery checks. Yeah, I know, you did some.

You said the resting voltage is 12.8v. Thats a good sign. Now with the meter on the battery, turn on the ignition. What is the voltage now?

Do you have a service manual? The manual says, and the wiring diagram shows, that the meter gets two 12v inputs. One is present all the time, and the other comes in when the ignition switch is turned on. The needles should sweep then. Could be an intermittent somewhere in the ignition 12v to the meter. It may be you have to open the meter and reseat/clean the connectors.

Why it works after started I don’t know yet. To me it indicates there isn’t enough voltage to operate the meter while under load but when the alternator comes up all is good. But then I wouldn’t expect the starter to have enough power to spin the engine but not drive the meters.

But one problem at a time. Check the voltage with ignition off, then on and tell us what the drop is.

Thanks for your input. I measured voltage today & get 12.45V with ignition off and 12.05V with ignition on. I know there's a difference now in the resting voltage to what I measured a few days ago however at that stage I had just taken the battery off the charging tender.

I had saved this procedure from an old post.

Honda CB1100 High Idle Problem
* Warm up the bike to get normal operating temp and idling
* Ignition OFF and remove the key from the ignition switch
* Disconnect both battery cables from the battery terminals, the negative cable first
* Cover both battery terminals with a plastic bag/rag to prevent accidental cable to terminal reattachment
* Join both cables (- &+) together for about 10 minutes. If the battery cables are too short, jumper wire can be used
* Reconnect both cables back to the battery terminals, the positive cable first, then the negative.
* Ignition ON, wait until meters sweeping is completed 2-3 sec, start your bike and observe idling.....

Thanks for this. Let me re-iterate- I do not have a problem with the engine idling too high- the idling is normal at all times whilst the engine is warming up & once it's warm. The problem is the momentary very high revs when hitting the start button...& it happens intermittently

[Charlie Bravo_imp]

I once accidentally twisted the throttle once when I started it up, and it jumped into life with what sounded like a mini explosion that made me jump too. Since then I turn on the key, pause for a few seconds, then touch the start button with one finger, not touching the throttle grip at all.