Might wanna also check out this thread geared specifically for the 390adv:

https://www.advrider.com/f/threads/390-adventure-owners-thread.1450567/

There are 700+ pages there, so you'll want to use the search function!

Do you know if they adjusted the clutch when it went in for its first service? Could be that its just not quite happy with where its adjusted. I'd mark the clutch cable's setting at the lever, then start moving it in or out to see if that helps the quickshifter to operate properly.

I too have a 390, its a '20, also installed a tip and Fuel-X (Pro for me) for the exact same reasons, incredibly white plug, (I have pics of the bosch after replacing with an NGK, that new plug made a big difference in the way it ran too), and I also have the quickshift installed. For me, its always felt "notchy" when shifting up and down, but no issues with it misfiring. It definitely cuts throttle between shifts, so if the clutch cable does nothing, I'm thinking something in the electrical portion of the quickshift is misaligned, perhaps loose, or something has been thrown out of whack inside the transmission.

Curious to hear what you find out about this!

 

Looks like you have the almost exact same issue that I have. I did some digging around and the answer to this issue has been sort of vague. Some talk about chain tension and adjustment, some talk about cush drive rubbers not sitting tight enough. My issue has gotten worse and the gear shifts feel incredibly hard as soon as the oil reaches a certain temp. The bike in itself is not overheating, but about 45 minutes into the riding the bike, you feel the oil viscosity changing and your shifts change a bit in feel and it gets hard and it has a notch.

I feel there is an issue with the chain tension, electrical issue with the quickshifter and some clutch adjustment issue. All these three done perfectly I feel will solve the issue. I am trying to get my hands on a service shop manual and I am haven't been successful yet. I shall work on this when I get one! Will keep you posted!

p.s. you have the had the most relatable scenario to my experience yet.
Thanks for the link, will check it out.

 

I got a adventure 390 rally edition and I've clocked around 2000 miles on it now. I moved from a 2013 Duke 390 to this and I really liked my previous bike . My first thoughts of the Adventure was it was super comfy to ride and the suspension once setup for my weight and road conditions was epic. However, I did feel the bike was running super choked and I felt the fueling was really bad, especially on the lower RPM's. Here started my troubleshooting on a brand new bike (Yikes)

1. I installed a FuelX module on the bike. I decided to do this after checking the plug on the first service, it was sparkly white. The bike was running extremely lean (I live at an altitude of around 1000m above sea level and the temperature here is usually between 77-90K). This is on a stock bike from factory, without any mods. I understand they need to meet modern emission norms, but running an engine this lean is straight up criminal if you ask me.
Anyways, after installing a FuelX (lite) module, the fueling became much better and the low end response and a major lean spot was covered with appropriate fuel going into the cylinder.

2. I got rid of the resonator and installed a exhaust with a mid-pipe from Red Rooster Racing. The design of the mid pipe is fairly straight forward and the end can is also well built. This change brought about a huge difference in the power delivery and behavior of the bike. Low RPM torque was instantly there, the throttle response became much much better and the bike started breathing freely. Really pleased by this change in my bike. I understand that this makes the bike leaner but I did inspect the plug after riding the bike for about 500 miles and the FuelX seems to be compensating for the change adequately.

Coming on to my problem, the quickshifter on the bike has been giving me problems probably after a month after getting the bike. Initially, the gear shifts on the bike were smooth and trouble-free with clutch upshifting and using the quickshifter. After the first service, the gearshifts, especially the upshifts became notchy and the quickshifter had a mind of it's own. Upshifts on the quickshifter became jerky and performed well only at high RPM's.

A couple of days ago, I finished adjusted the chain tension and did basic chain maintenance and now the quickshifter refuses to work at any RPM and the bike is misfiring at lower RPM's, almost as if the ignition kill from the quickshifter module is getting actuated randomly.

I switched off the quickshifter and everything is fine. So I have isolated the issue to the quickshifter. Now I need to know what I can do with either the quickshifter, gear lever or the shaft to make things work perfectly.

Any inputs appreciated.
Thank you!

I dont think this will help, but the only problem I have had with the quickshifter occurred after I adjusted the gear change lever position to accommodate adventure boots and new footpegs. My adjustment left to much gap between the boot and the lever, and I think there was something about my timing of the change. Upshifts were a bit hit and miss, especially in the lower gears.No missing at low revs though. Maybe check if the bike shop has adjusted the lever position. Only other thing that comes to mind is check if they used the correct oil, maybe the clutch plates are sticky.

 

They have adjusted the lever position and I didn't even ask them to do it. I got it back from them and I asked the guy why they did it and they said "since you had quickshifter issues, we thought this would help".
They gave it back to me with the quickshifter not working at all! I had to go on a ride the next day and I said **** it and have been riding it with the quickshifter off ever since.

I recently visited the dealership and the met the senior manager, he came by and said I will have to leave the bike at their shop for maybe 2 days and they'll fix it, I think it's a very bad idea.

I feel I should work on my own bike instead of trusting these guys here.

 

My '23 890 ADV R, quickshifter good at first, later becoming stiff and balky on upshifts . I basically just won't use it as much as I could. It can't be a good thing. It's at the dealer for other service, they told me they performed a software update. I don't know what it's about. I had not mentioned the quickshifter, not trusting of this dealer to tear into it. Sorry, mine is not a 390, but thought I'd mention anyway.

 

Apex Motorsport in Colorado Springs has a excellent service department

 

Thanks, good to know about Apex. My bike is still at Strictly Powersports in Pueblo West awaiting service to replace a leaking valve cover gasket.