Engine Shutting Off

naveed

Member
I have about 600 miles on my 2017 RC 390. A couple of days ago the engine shut off in traffic in second gear with clutch pulled in, the bike started back when I release the clutch. Today, I just started the bike to warm and it shut off after a minute of idling. I was wondering if this is normal or there is a problem with the bike.
 

isaac_

New Member
I have about 600 miles on my 2017 RC 390. A couple of days ago the engine shut off in traffic in second gear with clutch pulled in, the bike started back when I release the clutch. Today, I just started the bike to warm and it shut off after a minute of idling. I was wondering if this is normal or there is a problem with the bike.

Start by checking your connections. Ensure nothing came lose.
 

Tom

New Member
Screw that! Take it to the dealer before touching anything. You need to have the 650 mile service performed anyways.

If you bought a lemon, its best to start documenting that stuff ASAP.
 

mattv

Member
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I don't think it's uncommon for high compression singles to do that occasionally. I've had it happen. Definitely doesn't hurt to have a dealer look at it though. I would get concerned if it was a regular occurrence, but not the occasional idle shut off. I think I've had it shut off in low speed traffic twice in the ~3000 miles I have on it. Mine also has an exhaust, intake, piggyback, etc, so I can't reliably blame the bike for it.
 

John390

New Member
both my bike and the 17 demo I rode did this. The demo repeatedly and mine only a couple of times. Its not only annoying, but it could be very dangerous if it happened at the wrong time.

I am thinking its from the super lean maps, but I am not sure.

Both bikes did this when I was shifting from 3rd to second. As in, approaching a corner, or a slowdown in traffic. Clutch in, throttle to idle, downshift, it stalls. Mostly its hard to start again too, and when it does start, it runs poorly for a second or so.

Any info on this would be greatly appreciated. I am an auto service tech and also fiddle with high performance stuff on the side, so I know my way around machinery. I don't like this being unsolved.

Just had a thought.

I wonder if the clutch is dragging. Pull in the clutch, and downshift, but if the clutch isn't fully releasing, the drag on the engine when the lower gear meshes, combined with a high compression single cylinder and lean mixtures?
 

KneeDrachen

New Member
Mine did this twice the day I picked it up 2 days ago and just did it again this AM. I'm assuming it is a lean running condition as I had a SR400 that never did this.
 

KneeDrachen

New Member
Both bikes did this when I was shifting from 3rd to second. As in, approaching a corner, or a slowdown in traffic. Clutch in, throttle to idle, downshift, it stalls. Mostly its hard to start again too, and when it does start, it runs poorly for a second or so.

EXACT same thing with my 2018
 

KneeDrachen

New Member
Make sure there is still about an inch of dead spot in the clutch pull. Also verify the cable tension spring on the case cover is installed correctly. It looks like the arm of the spring could easily slip from the side of the case cover due to a lact of any detend or holder. See https://www.rc390-forum.com/forum/engine-and-technical-discussion/1308-clutch-spring-pop.html

by "dead spot", do you mean free play? My lever as set up has zero slack in it as set up from the dealer, 130 miles on it now.
 

Tom

New Member
The term "play" can be confusing, as the clutch levers allow you to move the lever past the normal resting position (away from the handle bar), which can be confusing if not described in detail. By dead spot, I mean that from the clutch lever's normal resting position, there should be an amount of no resistance until the clutch lever starts to tension exponentially, meaning the clutch is actually disengaging. The manual calls for 1 to 3 millimeters of play or as I call it dead spot.

Now, this is the important part. Our clutch levers have adjustments from 1 through 5 on the silver dial. Most people mistake this for comfortable length of pull, and wrongly determine it as a "set and forget" setting. While the "5" does set the clutch lever closest to the handle bar, and "1" does the opposite, these setting have nothing to with what is most comfortable to your delicate little hand. They are in-fact setting the actual engagement/disengagement level of the clutch, and are to be used to compensate for the thermal expansion of the clutch assembly. (KTM's ready to race philosophy, but built with cheap parts)

You can test this by setting the dial to "5" and using something to tie the clutch lever so that it is at the maximum pull on the handle bar. Next, use a marker to draw a straight line down the coils of the exposed spring located on the top of the clutch cover. Next remove your Macgyver-ed clutch lever pulling device (string or zip-tie) holding the clutch lever at max pull, and set the silver dial to the "1" position. Now pull the clutch back and look at the line you drew on that spring. Not so straight anymore, is it?

There should always be a dead spot in your clutch pull no matter what the dial is set to. You will still see the spring and actuating arm on the clutch cover move during the take-up of this dead spot, but there will be very little resistance in the pull. If you choose to take most of this dead spot out, do it while on the "1" setting on the dial.

If your clutch lever, is truly as you say with zero slack or dead spot, then you are actually not fully engaging you clutch with the lever out in. Meaning, as your motor and clutch plates warm up, you are dragging the clutch plates even though you think the clutch is fully engaged. This in turn causes more friction, and more thermal expansion, to the point that there is enough grip left between the plates to stall the motor even though things seemed "normal" when the friction plates were cool.
 
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KneeDrachen

New Member
Adjusted free play at the lever end while on the "1" setting, and same thing, died on my shifting from 3 to 2. I've noticed if I excessively blip the throttle (more RPM than I normally would) during the downshift, it helps prevent the engine from stalling or if I downshift at a higher RPM and let the slipper clutch work its magic, it also helps.
 

Tom

New Member
Nah, that looks exactly as mine does. From your last description it sort of sounds like it could be a bad 02 sensor. At this point I think the best next step would be to take it back to the dealership and let them replicate and troubleshoot the issue.

Sorry I couldnt be a better help, but I think pulling any potential codes from the ECU and checking/swapping the o2 sensor is something that should be performed on the dealership’s dime for a vehicle that is still under warranty.
 

Karfanatik

Active Member
Country flag
can you tell what was the issue? and how was it solved!
I had a brief moment of stalls under deceleration with the clutch pulled and no throttle. I quickly adjusted the clutch cable (not lever adjustment) and done deal. Hasn't done it since.
 
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