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Yes, that appears to be the stepper hose.
Valve adjustment could be a contributing factor...
A stepper motor‘s mission in life, is to adjust the mixture to set idle speed.A malfunctioning stepper is more likely to produce a fluctuating idle speed, than a roughness as such. I would simply leave the electric plug hooked up, but blank off the air feed and witness the result. If your stepper is being wrongly commanded, or simply sticking, then the electric servo will still malfunction, but the air/fuel ratio will not alter in unison.This will leave you with an idle at incorrect speed, but should not continue to fluctuate.Have you balanced the TB’s and set the idle balance by the correct method ?I trust your sacred screw has not been molested ?
I think the right hand hose with the split is the tank vent line to the tip over valve. As Steve has mentioned a proper tune up is due, Valve adjustment could be a contributing factor also throttle body balance and tps and self learners reset. When balancing the TB's , only one air bleed screw should be opened on the side with the highest manifold vacuum. A quick search on tuning the moto guzzi 8v will get you all the info needed. Also check your airbox and filter to see if there is an abundance of oil in there . If you have been running the oil level to the full mark on the dipstick , it is a possibility , The 8v's will expel oil out the case vent until they find their happy level. On mine it seems to be about two thirds up the dipstick range.
The hose w/black arrow goes into the airbox, red arrow(same hose) goes to stepper. Disconnect black arrow end from airbox to spray cleaner into end.Silicone spray will lubricate the stepper for better operation.If you undo the intake rubber snorkels hose clamps, you can remove airbox a bit back enough to clean the TB's. I do mine every 10K mi and it always runs smooth.After 19K mi I would think you need a tune-up.
By “rough”, do you mean surging like this does for 30 seconds when cold ?https://youtu.be/Li8qvFVuAJ8
I see your bike is an 8V.Norge/Sport/Griso/Stelvio……?I would have the airbox off, remove the stepper motor and spray the internals with penetrant while actuating the key. You’ll see and hear the stepper whirring as it activates.Get some carb cleaner in there, or better still install another if you can borrow a known good one.Check the connections on the relevant temp sensors on your motor, you may be getting poor data to your ECU when cold.Check all the hoses and clamps on the plumbing around the stepper.Again, if you temporarily block the air supply to your stepper, you’ll be able to see if the symptom disappears or changes.Or you could unplug it for the test.You see, the stepper is the sole means of adjusting the idle rpm, it does so by operating a small servo motor within the body, which turns a threaded needle which operates in an annulus….(small hole), very similar to a needle and jet in a carby.The engine has a target RPM and the ECU “knows” if the revs are above or below this value, it commands the stepper to raise or lower the needle, altering the idle mixture and therefore RPM.You have not fully clarified if your idle is “rough” or “pulsing”.Yes that’s my V85.I did a thread a while back called “V85 facelift”, outlining the steps I took to get it to where you see it now.https://youtu.be/W9ulUhJgVwk
Check you air bleed screws to make sure only one side is open. They are a brass ,5mm allen screw in the bottom of either TB facing downward . They tighten clockwise to close. Not always does one need to be open but never should both be open. My 8v griso's tb's balance out with both closed as long as the valve gaps are spot on. As Huzo said, make sure all the hoses are in good shape. Also, don't be afraid of Guzzi diag as it is a wonderful and necessary tool to home service a FI guzzi. There is an excellent tutorial on its use here: You will need it to check/ reset your TPS and self learning parameters as well as checking for diagnostic fault codes stored in the ecu. and a lot more including checking stepper function. https://wildguzzi.com/forum/index.php?topic=96957.0
I have the pulsating idle at the first start up of the day, especially if the bike has sat for a few days. What does this mean?It is much more aggressive than that video posted. It smooths out within about a minute if I just let it warm up and then it's good for the rest of the day.
I’ll bet my left one that it’s being commanded by the stepper.Now maybe the stepper is over compensating and allowing the revs to drop too low, then the ECU realises and commands the stepper to open….But by a bit too much.Which then over revs the idle.So…The stepper closes the needle but a bit too much…The target rpm figure is being missed by a couple of hundred each side, until it zero’s in on the correct figure and trims out the highs/lows.Just a guess of course.If I wanted to, I could pull the plug on the stepper while it’s oscillating and I’d know immediately if it’s stepper generated.But I choose not to care..By the time I’ve scratched my butt and put on my gloves, it’s settled down predictably.
Not that I’m suggesting you do this as I don’t know where you live(real cold climate), but the stepper motor was giving me similar trouble on my 07 Norge and I kept it wired up and installed rubber caps on the stepper motor. On cold NY days it took a little while to get it warmed up, but end of problems and this was about 12 or so years ago.
Yes mate.It’s just a normal V85 with some bits taken off and thrown in the bin and a couple of altered bits added.I’m sometimes asked how I got it looking like that….I just cut away the bits that didn’t…
Pete Roper, who many know of, has suggested that the bike is busy purging it's charcoal canister which is loaded up with evaporative when it's parked in the heat.