IAC Valve knowledge

Is this already known? If so, please let me know and I will delete the post.

I am new to the 961 and was struggling with getting my 2015 961 Commando SF to idle.Acheiving an idle required throttle input to start and constant throttle attention to get it to a point where it would idle after 2 minutes or so.
Endeavoring to find a solution that didn't involve a new ECU or re-engineering the fuel/air system I took apart the IAC and started poking around when I noticed that the IAC Plunger was no where near long enough to actually impede air flow through the attached air port even with the bike running.
My "solution" was to plug in the IAC motor.
Turn on the bike but not start it.
Watch for the IAC plunger to extend the 10MM or so (that seems to be a preset limit).
Then unplug the IAC with the bike still on but not running.
Turn off the bike.
Plug in the IAC motor and again watch it extended an additional 10mm or so.
At this point the plunger is within reach of the port to restrict airflow at the next extension of the IAC plunger.
Unplug the IAC Motor with the bike on but not running.
Turn off the bike with IAC unplugged so the plunger doesn't retract on turning off the bike.
Re-assemble the IAC motor and port and remount it to the bike.
Once mounted in the plunger extended (twice) position the bike fired up and idled as one would expect. i.e. no need to touch the throttle to start or maintain idle.

I haven't seen where this is discussed previously on the forum and thought I would reach out to see if I have discovered something previously unknown or simply fell out of the boat to "discover" water is wet.

Again, if this is a known "thing" with the bike let me know and I will remove the post to eliminate any confusion.

Thank you, all of the tips and tricks posted through out the forum have been incredibly helpful in getting this bike running again.

Interesting discovery. The IAC has been discussed here before but more in the context of why it doesn't work rather than how does it work. Some have found that blocking it off is better and others have no Issue.

I was surprised to see that it didn't seem to be discussed previously. I was more surprised to see that Norton apparently installed the part without setting the "starting" position for the IAC valve.
But with that said I have no previous knowledge of IAC valves or anything more complex but I do OK smacking things with a wrench until they make sense to me.
I failed to mention in the previous post that my discovery came the 4th time I took off the IAC and stared at it. Edited inspiration is always better than the straight facts.

NonSequiterRex said:

Is this already known? If so, please let me know and I will delete the post.

I am new to the 961 and was struggling with getting my 2015 961 Commando SF to idle.Acheiving an idle required throttle input to start and constant throttle attention to get it to a point where it would idle after 2 minutes or so.
Endeavoring to find a solution that didn't involve a new ECU or re-engineering the fuel/air system I took apart the IAC and started poking around when I noticed that the IAC Plunger was no where near long enough to actually impede air flow through the attached air port even with the bike running.
My "solution" was to plug in the IAC motor.
Turn on the bike but not start it.
Watch for the IAC plunger to extend the 10MM or so (that seems to be a preset limit).
Then unplug the IAC with the bike still on but not running.
Turn off the bike.
Plug in the IAC motor and again watch it extended an additional 10mm or so.
At this point the plunger is within reach of the port to restrict airflow at the next extension of the IAC plunger.
Unplug the IAC Motor with the bike on but not running.
Turn off the bike with IAC unplugged so the plunger doesn't retract on turning off the bike.
Re-assemble the IAC motor and port and remount it to the bike.
Once mounted in the plunger extended (twice) position the bike fired up and idled as one would expect. i.e. no need to touch the throttle to start or maintain idle.

I haven't seen where this is discussed previously on the forum and thought I would reach out to see if I have discovered something previously unknown or simply fell out of the boat to "discover" water is wet.

Again, if this is a known "thing" with the bike let me know and I will remove the post to eliminate any confusion.

Thank you, all of the tips and tricks posted through out the forum have been incredibly helpful in getting this bike running again.

Click to expand...

The IAC has been covered in numerous other posts, and the reasoning for blocking is discussed.

The problem with the IAC is that the ECU supplies the voltage, not the IAC itself. If low voltage is present, the IAC will actuate improperly, which causes poor starts and poor running. With a fully charged battery and a good start, the IAC typically isn't an issue.


We have worked on numerous bikes where the IAC isn't blocked, and with a lithium battery, the system works great(and using a typhoon).

I would also caution plugging and unplugging the IAC from the ECU. Good way to short out the ECU

This technology is from the 1990s, so it's not perfect.

As far as I’m aware, the IAC valve is a solenoid controlled plunger which is either fully open or fully closed - is that a correct assumption?

cliffa said:

As far as I’m aware, the IAC valve is a solenoid controlled plunger which is either fully open or fully closed - is that a correct assumption?

Click to expand...

No , There are steps in between full open and full closed. Usually its not full open Idle would be high.

TonyA said:

No , There are steps in between full open and full closed. Usually its not full open Idle would be high.

Click to expand...

Tony, I think in another thread you said that you removed a small amount from the face of the IAC housing to enable the valve to close properly. How did you determine that it wasn't fully closing?

comet said:

Tony, I think in another thread you said that you removed a small amount from the face of the IAC housing to enable the valve to close properly. How did you determine that it wasn't fully closing?

Click to expand...

It was Idling too high. I had set the throttle valves to be almost closing with 0 throttle . I had the bike idling good this way with the IAC installed. What finally made me remove it was the tendency for the bike to kill at abrupt stops. It was as if the IAC couldn’t keep up .

Maybe it needs to be lubricated? This was something we had to do on the Ducati Sport Classic when I owned one. Spray some WD40 in where the plunger is. I'll admit though that I've never had the Norton one off the bike so I cant tell if its exactly the same set up but might be worth a try

speirmoor said:

Maybe it needs to be lubricated? This was something we had to do on the Ducati Sport Classic when I owned one. Spray some WD40 in where the plunger is. I'll admit though that I've never had the Norton one off the bike so I cant tell if its exactly the same set up but might be worth a try

Click to expand...

Not a valve issue. We tried multiple new ones, and with lots of electrical engineering, it was always the ECU, the voltage, and the wiring that caused the issue. Never consistent

Bin it, block the crossover, never ever look back.

Seriously.

Gojuu said:

Bin it, block the crossover, never ever look back.

Seriously.

Click to expand...

Just to clarify is that for all ECUs? I have never had an idling issue with my 2017 CR but obviously there is a lot of discussion about unbalancing the cylinders across that crossover pipe...

So if the IAC the cause of the occasional hi idle all I need to do is block it ?
And the only difference would be to idle using throttle for a few seconds when the bike is first started?
Do I need to reconnect those O2 sensors afterwards?

Clive said:

2016. Just to clarify is that for all ECUs? I have never had an idling issue with my 2017 CR but obviously there is a lot of discussion about unbalancing the cylinders across that crossover pipe...

Click to expand...

I have been told that the OMEX ecu does a better job of driving the idle motor than the SC does. I have never had an OMEX , my bike had the SC . This may be one of the reasons Norton went back to OMEX in 2016. At the time my choice was between upgrade to OMEX from Norton or get the Delta 400 from SCS. It was an easier upgrade with SCS .

speirmoor said:

So if the IAC the cause of the occasional hi idle all I need to do is block it ?
And the only difference would be to idle using throttle for a few seconds when the bike is first started?
Do I need to reconnect those O2 sensors afterwards?

Click to expand...

You can keep the O2 sensors in place and continue using them. Yes set the idle screw when engine is hot and use a lock nut on it. You should block the passage between , this is the best way .

Does anyone remember the size/diameter of the allen screw that adjusters the idle? My iac has been blocked and my set screw is set in a good spot. So I’m hoping to add a nut over the screw and not have to throw it out of adjustment. Hopefully this makes sense?
Thanks!

Is blocking the IAC and blocking the crossover 2 different things?
Anyone got pictures of what they've blocked?
Heading to the garage later and want to get my ducks in a row.

Charlotte said:

Does anyone remember the size/diameter of the allen screw that adjusters the idle? My iac has been blocked and my set screw is set in a good spot. So I’m hoping to add a nut over the screw and not have to throw it out of adjustment. Hopefully this makes sense?
Thanks!

Click to expand...

M3 or M4 one or the other.

TonyA said:

M3 or M4 one or the other.

Click to expand...

The nuts were easy to find at Ace Hardware store in stainless steel. It helps to get a slightly longer set screw to give you more length to work with. These were also available at Ace Hardware store .

speirmoor said:

Is blocking the IAC and blocking the crossover 2 different things?
Anyone got pictures of what they've blocked?
Heading to the garage later and want to get my ducks in a row.

Click to expand...

Two seperate sets of actions - widely covered; do a thread search on ‘idle’.

Start here, where iwilson provides images of blocking the crossover that will clarify.

Thread 'Idle problem solved'
https://www.accessnorton.com/NortonCommando/idle-problem-solved.27459/

Good luck, and document what you find mate - no doubt it will help the next owner to have a go.