2018 RC390 Stalling (Yes, I know it's a common issue and I've searched)

acruhl

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(Reviving this)

Ok, I have my own story here but I want to clarify something:

Stalling at low engine speeds is totally different than stalling due to an electrical problem (such as sidestand sensor or spark plug wire). They really don't even belong in the same thread. Decide which problem you have and follow that path.

Riding somewhere at wide open throttle or near it and the bike cutting out suddenly or sort of stuttering is almost certainly an electrical problem. Loose ground on the battery, loose spark plug cable, failing sidestand sensor, something like that. This is a very common thing for racers to experience as they modify the bike for racing. Been there, done that.

Stalling at low RPM as you close the throttle coming to a stop is almost certainly a fueling/mixture problem, or some other thing the ECU can't handle to keep the engine running. This was very common in the carburetor days.

I'm highly skeptical that adjusting the valves would affect this problem unless they were way, way off. It's much more likely that you inadvertently solved it with all the stuff you have to do to take the bike apart and put it back together. But I'm willing to be educated on that one. I suppose the minute changes in cam timing and lift due to out of tolerance clearances could cause some airflow changes. (3 out of 4 of my valves were tight when I checked them at about 800 miles. Adjusted with shim kit from Amazon - more in the valve adjust thread.)

I had the stalling at low engine speeds issue happen after I put on a Yoshimura 3/4 exhaust, K&N air filter and new NGK spark plug. I assumed the bike is now way too lean for the ECU to deal with it and I need a tuner of some sort to bring it back. But it magically fixed itself after I rode to high elevation and the temperature warmed up. When I put my finger in the exhaust I get no black on my finger for example.

I'm exploring my tuning options. Guessing I will need the bigger injector too.
 

Xquzme

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Hello, new to the group and my son and I have a 2016 KTM 390 RC.

We recently did the valve adjustment for the 16000 Km's (Canadian Model) I am having the stalling issues when gearing down as well and hard start once the bike is warm. All the valves needed some adjustment ( all tight) so we replaced the shims and checked clearances. We were able to get the gap's within spec. While in there were replaced fuel filter, air filter, oil and filter, new plug.

We got the bike running off cold no issues but once warm she is a bitch to start. We tested the battery and found it was weak so we replaced it thinking there was low current for start up. Unfortunately, that didn't fix the issue.
Now I am thinking maybe cleaning the throttle body and testing the injector.

Thoughts?
- Do I try cleaning throttle body?
- Do I take it in to get mapped or scanned?
- Could the injector be an issue?
- Is my valve adjustment the cause?

The bike road well before the valves were adjusted so I kinda think that maybe the culprit. I also think the ECU needs to readjust due to the new clearances.


Any thoughts would be appreciated. I have a 16 year old that is itching to ride this thing but it isn't reliable or safe to ride on the road.
Thanks

Todd
 
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ReidMcT

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One thought not yet mentioned in this thread: Get a better spark plug boot. One of our sponsors sells them. A forum search should yield the specifics for you. I installed one and it stopped an occasional stalling problem that was starting to develop.
 

acruhl

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Yeah I was going to say put in a new spark plug for similar reasons.

Temperature related stalling is almost certainly mapping - a lean condition in the case of heat. If you mix that with bad spark, then there you go.

Could be the EGR or some other sensor as well.

Remember, these are cheap bikes. This stuff can and will fail.
 

yana

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Ok. Just found this topic after a google search of: KTM RC390 stalling. I had this yesterday, second ride on my 'new'(to me) bike. Its a 2018 model, 6200km on it.
It was warm (fan was running 20 seconds ago when I had to wait at an intersection). I drove on, geared up upto 4th I think, that had to brake for 2nd gear turn and it stalled. (I mightve been in first accidentally, Im still getting used to it) at low speed. (10km/h maybe dunno). First I thought it was me, not pulling the clutch soon enough, but now Im not so sure anymore.
It has standard exhaust etc. Its all standard.
I do tend to blip the throttle when downshifting. Im used to that from the 2strokes. Does that have an affect?
Ill look at the cluch lever adjuster. Only thing I can do myself.
 
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