Stepper motor acting up

Small update on this. The manual valve was not a very elegant solution and a new stepper was too expensive, so I decided to come up with my own solution.

I bought a thermal switch triggering at 60°C (NC) and put it in series with a 12VDC solenoid valve mounted on the pipe between the air box and the stepper motor. The thermal switch will be glued with thermal epoxy between the fins of the left cylinder.

Here is a schematics of it:
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I did quick proof of concept on the bike and it works well. I'm currently waiting for watertigh connectors and I have to determine exactly where I want to glue the switch on the cylinder so that the circuit is broken at the right engine temp.
I will post installation pictures as soon as I get the missing parts.

Btw could I completely remove the stepper and use the mounting holes to put the valve? Would that be a problem with the ECU?

If you disconnect the stepper it will trigger a service warning on the dash.

Mine acts up in some pattern of randomness that I haven't quite figured out. Would relative humidity mess with it? It seems like it sometimes hangs up on the first pause (stop sign, etc) of the first ride of the day, and more so when there is morning fog or precipitation. The rest of the time it idles as it should to the point where I've never worried about messing with it.

They get intermittent as they age. I doubt if RH has anything to do with it, certainly being "cold" would affect it. It will get worse, George.

Living in Texas, you could probably block it off all together, without issues, apart from a low idle from first start. Mine has been disconnected for 7+ years and even starts in temps as low as 0C (32F for you) - it might need a touch of throttle for 10-20 seconds, that's all. If you do block it off, don't forget to block off the spigot under the airbox.

Oz1200Guzzi wrote:

They get intermittent as they age. I doubt if RH has anything to do with it, certainly being "cold" would affect it. It will get worse, George.

Living in Texas, you could probably block it off all together, without issues, apart from a low idle from first start. Mine has been disconnected for 7+ years and even starts in temps as low as 0C (32F for you) - it might need a touch of throttle for 10-20 seconds, that's all. If you do block it off, don't forget to block off the spigot under the airbox.

Thanks Don. I will try that route.

Hi, regarding the opening of the Steppermotor, i have done this . You can lift it after removing the clampspring, then you can unscrew the "Motorpart" from the Valvepart. I have posted this in the Guzzienduro.org - Forum. I didn't reinstall the Stepper, because have purchased a new one for a still horrible, but reduced price.
Greetings from Germany in Springtime!

XU12 wrote:

Hi, regarding the opening of the Steppermotor, i have done this . You can lift it after removing the clampspring, then you can unscrew the "Motorpart" from the Valvepart. I have posted this in the Guzzienduro.org - Forum. I didn't reinstall the Stepper, because have purchased a new one for a still horrible, but reduced price.
Greetings from Germany in Springtime!

Hi XU12 !
I tried to connect to the Guzzienduro.org forum but topics cannot be accessed by guests
Would you be kind enough to post it here too ?

I am facing some difficulties with my stepper motor that seem to "partially" work only (I can feel it "resetting" when switching off getting from open to fully closed and re-opening afterwwards when !I blow in the tube connected to airbox) but it seems to not open on cold start-ups resulting into very low rpm's till engine warms up a bit.
Reading the Base + Control + Break values of Stepper motor in Guzzidiag shows that ECU seem to ask for valve to open (Control value rises to 100) but Base value remains unchanged whereas, to what i found, it should rise up.
Therefore, I think it can close  ...but it cannot open completely despite my attempt to clean ith with carb cleaner sprayed from airbox tube So, if it can be opened, I may then be able to clean also the normal to full opening range !

I found that you can get a replacement motor assembly off fleabay for a reasonable price but I haven't successfully managed to get it to clamp in position in the aluminium body; there's a serrated washer around the motor assembly.

you also have to swap over the brass plunger assembly with the plastic bullet plunger.

I think I have seen a picture of a full plastic version of the stepper motor (can't remember where)

Gave up in the end

Mine is a full plastic stepper "motor" if you are talking about the complete Idle Control device (My GRiSO is one of the last made in 2016).

In my case, the electrical motor seem to work but my assumption is that it can run from "default" semi-open position to fully close but it can fully open. So I am just wondering if the electrical motor can be removed to inspect what keeps the plunger from fully opening.

Evilgarfield wrote:

Small update on this. The manual valve was not a very elegant solution and a new stepper was too expensive, so I decided to come up with my own solution.

I bought a thermal switch triggering at 60°C (NC) and put it in series with a 12VDC solenoid valve mounted on the pipe between the air box and the stepper motor. The thermal switch will be glued with thermal epoxy between the fins of the left cylinder.

Here is a schematics of it:
[You must be registered and logged in to see this image.]

I did quick proof of concept on the bike and it works well. I'm currently waiting for watertigh connectors and I have to determine exactly where I want to glue the switch on the cylinder so that the circuit is broken at the right engine temp.
I will post installation pictures as soon as I get the missing parts.

So I finally had time to implement my idea to replace the function of the kaputt stepper by a solenoid valve.

I started by epoxy the thermal switch on the wall of the cylinder
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I then fixed the solenoid valve with a bracket between the stepper and its mount and tucked the connectors next to it.
[You must be registered and logged in to see this image.]

And plugged the whole thing on a switched output of my eastern beaver harness so that it does not drain my battery when the bike is off.
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I tested it yesterday and today and it works perfectly. I started the bike cold on a chilly morning (3°C) and it cranked up right away and settled at 1100RPM. I rode away and never had a high idle over the 2h ride. Today I repeated the test with 23°C and same again, no high idle when warm or rough when cold.  

It might be overkill but at least it's working as it should and it costed me less than 20 bucks.

Unless you use your bike in very low temps, less then -4 Celsius that I tend to experience I wouldn't worry about having the valve or stepper, I've not noticed any issues and you can always let the engine warm up for a bit longer should you wish. I think I must have had my stepper removed for the last 3 or 4 years and ride all year round.

I have some very cold mornings but it was more about a quick fix to have a bike setting nicely to that 1100 RPM idle whatever the temperature than worrying about it.

Let's call it a quality of life change

My idle was erratic so I plugged up the stepper motor and that solved it. Do I need to balance the throttle bodies and reset the TPS now?

Should be good, just ride...

Personally I'd rebalance the air bypass and probably higher rev balance as well, because presumably you've closed off both air feeds from the stepper (or blocked feed to them)??.

I'm not sure why (& can't be bothered to find out), but my GRiSO won't idle with the stepper feed blocked & I think would then have to have more bypass air to get it back to stable idle.

paulbrice wrote:

Personally I'd rebalance the air bypass and probably higher rev balance as well, because presumably you've closed off both air feeds from the stepper (or blocked feed to them)??.

I'm not sure why (& can't be bothered to find out), but my GRiSO won't idle with the stepper feed blocked  & I think would then have to have more bypass air to get it back to stable idle.

I blocked the air feed to the stepper without rebalancing and it seems to idle and run nicely. I'll check the balance though for good measure.

BrianD wrote:

Unless you use your bike in very low temps, less then -4 Celsius that I tend to experience I wouldn't worry about having the valve or stepper, I've not noticed any issues and you can always let the engine warm up for a bit longer should you wish. I think I must have had my stepper removed for the last 3 or 4 years and ride all year round.

Hey Brian,

What bike did you do this to? Did you do anything extra beyond plugging up holes and capping off ports?

I've got the Stelvio 1200 4V 2008 year and I'd like to clean the stepper motor. Due to really hard access to this part in Stelvio, is it possible to clean stepper motor through other pipe (which I circled on the picture). It is connected with LH airbox spigot. I will be grateful for your help [You must be registered and logged in to see this image.]

First question is has your bike been rollerised and if not how many kms are on it?

Second question is how has the bike been tuned? And by whom? Did they know what they were doing?

Oh, and we are more than happy to try and help Stelvio owners. In fact if we can we'll try and help anyone....

Thank you for fast feedback!  [You must be registered and logged in to see this image.] Yes, I've already done by myself the rollerization with "C" set. Valve clearances are adjusted, 0,10 mm inlet and 0,15 outlet. TPS is reset. I'd like to do also TB balance, but I'm waiting for new manometer. I've also upload the Beetle map for Stelvio after rollerization and GPR exhaust without catalyzer.

The main problem is after the rollerization idle is too small, around 800-900. It slightly increases when warming. But it's not higher than 1000. So idle is a bit rough. As I know, idle depends on proper stepper motor working and well balanced TB's. Correct me if I'm wrong.

I've read about fast method to clean the stepper motor via pipe from airbox, but only accessible pipes in Stelvio 2008 (european version without carbon canister) without completely dismantling everything are two ones on the bottom of airbox (closer to the engine compartment). One of them (RH) is going to the front of the frame, and the LH pipe (circled in the picture) is going to the stepper motor. Is it proper place to use carburetor cleaner?

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Hey Adobe! I have a Stelvio and recently cleaned out a pretty bunked up stepper motor. Mine is a 2014 8v, but I think it should be similar enough.


The first picture could work. The second pictures would not because it would dilute the carb cleaner to basically nothing by the time it got to the stepper motor.

I did it through the top by flipping the battery around and using a metal straw. This allowed me to spray some in, let it sit, then run the bike while spraying some in (and revving the engine up so it didn’t die). I’ve attached pictures.

Worked well for me! Good luck!

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Thank you for your answer and help! But unfortunately the 2008 year airbox is different and the stepper motor is not accessible when you disassemble the battery and its rubber support. It's only possibility to take off the cover mounted by 4 screws.

Ok, I solved the stepper motor access problem in Stelvio 4V 2008. Just remove the airbox. [You must be registered and logged in to see this image.] Applied a large amount of cleaning agent and started the stepper motor. Thank you for your help!