High engine revs on start up

[Cormanus]

If you wait until the gauges finish sweeping and the fuel pump cycles the high revs shouldn’t occur.

[CBX1000_imp]

If you wait until the gauges finish sweeping and the fuel pump cycles the high revs shouldn’t occur.

Well that's just the problem; sometimes the gauges don't sweep at all until I press the start button & only then do they sweep fully together with the engine revving high for a moment.

I suspect that this is going to be a difficult issue to resolve...

[Cormanus]

May well be, CBX1000. Can you just time it to the fuel pump cycle? You hear that pretty clearly.

[CBX1000_imp]

May well be, CBX1000. Can you just time it to the fuel pump cycle? You hear that pretty clearly.

The fuel pump cycles every time I switch the ignition on (except when the kill switch is on, which is correct) so that appears to have no bearing on why the gauges randomly don't sweep & then produce the high revs on start up.

[Cormanus]

Sorry to belabour this, CBX1000, but, if you turn on the ignition and wait until the fuel pump cycles but the gauges don’t sweep, do you get the high revs? Or do you get the high revs only if you hit the start button before the fuel pump finishes cycling?

[CBX1000_imp]

Sorry to belabour this, CBX1000, but, if you turn on the ignition and wait until the fuel pump cycles but the gauges don’t sweep, do you get the high revs? Or do you get the high revs only if you hit the start button before the fuel pump finishes cycling?

The answer to the first part of your question is yes- I get the high revs without the gauges sweeping even after the fuel pump has cycled. As a rule I only hit the start button once the fuel pump has cycled- the cycle is actually pretty quick....essentially by the time you've turned the ignition on & then got your hand back to press the start button the pump cycle is already done

[Cormanus]

Right. Thanks. That one’s way beyond my pay grade, I’m afraid. It’s an odd thing to happen.

Maybe one our seriously knowledgeable members can help.

[Karidis]

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.....

[peterbaron]

The above procedure is known as ECU residual reset.
I use this method very often.
This may help permanently if no other hidden or intermittent problems occur or after replacing an electronic component.
Sure, it's good start and costs $0
In this particular case, when the engine is hot and at operating temperature, I would wiggle the TPS connector and watch the rpm.
Do one step at a time and start with wigling the TPS connector/3 wire

[Lord Popgun]

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.