Got the dreaded engine cut off symptom

HuskyGabe

fast rider
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Jun 19, 2021
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Oakland, CA.
Alrighty, I’ve got a little over 400 miles on the clock and have begun to experience the common engine cutoff upon downshifting. Has anyone found a solution to this yet? I’ve read mixed results on the forums indicating the eradication of the cutoff symptom after getting the initial 600 mile service ECU update/reset. An additional question is if anyone knows if the Coober ECU upgrade rectifies this engine stall issue? I’m thinking of getting this upgrade after the initial 600 mile service. Any info would be appreciated.
 

Geeves32

contributing rider
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Aug 3, 2021
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Michigan
21 model just got back from dealer its a intermittent problem even after the check up. Fix: pull in clutch and restart on a role.
 

Vintage Veloce

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San Diego
I have yet to experience this.
What are your revs in the destination gear when this happens? Does it happen at "higher RPMs", say above 3k in the destination gear?
Sometimes I wonder if some of the problem is just unfamiliarity with larger single cylinder engines. They do have a propensity to stall if you downshift at lower RPMs. A multicylinder has other cylinders pushing the crank around...
 
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HuskyGabe

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Oakland, CA.
I really can’t say what rpms it happens, only that it does when down shifting. I hate to be vague but I can say that the RPMs are not high. Maybe around 3000 or less. Hard to say with a non numerical, digital tachometer. I know we have RPM bars, but when downshifting, I’m more cognizant of the road than of what RPM bar I’m in.
 

Vintage Veloce

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I do think some definitely do have a problem that may cause stalling when downshifting, so you do want to check on that.
The slipper clutch really should really eliminate any harsh downshifts, but it's worth a moment of self checking:
It IS easy to stall a single cylinder bike when downshifting at low RPM. It is something to pay attention to on your next ride and consider. If it stalls on a smooth easy downshifts with matched revs and a smooth clutch release that's more likely to be a bike problem, but if it stalls on a harsher downshift at low RPM... well, maybe try adjusting your technique a little and see if it still happens. I stall my dirt bike doing that regularly.
 

BISavage

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I had someone explain this to me one time awhile back; when the clutch gets pulled the bikes ecu switches maps to the "clutch pulled" map.

There are alot of factors involved which is why some do not experiance it as often as others.
 

Vintage Veloce

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Yeah, I'm not saying there isn't a technical bike problem on some bikes.
I'm just noting that as someone who owns four 4-stroke single cylinder motorcycles, they are easy to stall on downshifts.
I'd hope the 401's slipper clutch would solve that for most people. But like I said, could be a real technical problem.
 

BISavage

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Yeah, I'm not saying there isn't a technical bike problem on some bikes.
I'm just noting that as someone who owns four 4-stroke single cylinder motorcycles, they are easy to stall on downshifts.
I'd hope the 401's slipper clutch would solve that for most people. But like I said, could be a real technical problem.
Absolutely agree, its not 401 specific, its 4 stroke single specific.

Would like to point out though that Coober makes their ecu to dial in the performance of the engine's ignition & fueling, for each gear; a side effect is that the downshift stall thing goes away... or so I have heard.
 

Vintage Veloce

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I think what happens is this...
You pull in the clutch and the engine runs fine with no load.
You let out the clutch and the suddenly loaded engine turns over at an unpredicted speed and the fueling/ignition may fail to ignite the charge. At low rpm, this single misfire is enough to stall the bike.
It's a tough technical problem.
 

travistravistravis

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Jan 13, 2021
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Oregon
It's happened to me several times well before hitting 1k miles. I can't remember a single instance in the past 200-300 miles. I blamed it on the clutch switch at the time.
It would happen just from pulling the clutch in while coasting (3,4,5,6 gears, over 20mph, pull clutch in - dead).
 

joeprez

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Oct 16, 2020
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USA
Sometimes I wonder if some of the problem is just unfamiliarity with larger single cylinder engines. They do have a propensity to stall if you downshift at lower RPMs. A multicylinder has other cylinders pushing the crank around...
Mine still does it (2019 401 Svart), and I believe it may be what you wrote... it only happens to me when downshifting at lower rpms and when the clutch is engaged (if I downshift without pulling the clutch lever, it doesn't happen). So now I rev match in my downshifts and problem solved (still get a stall now and then). I will tell it to the dealer in the next service anyways, maybe try to have the ECU reflashed by them.
 
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HuskyGabe

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Jun 19, 2021
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Oakland, CA.
This is all great info. Thanks to everyone who contributed. I’ll be getting my 600 mile service done this coming weekend then looking into getting the Coober ECU mod and see what comes if it. Hopefully this takes care of the issue.
 

joeprez

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Oct 16, 2020
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This is all great info. Thanks to everyone who contributed. I’ll be getting my 600 mile service done this coming weekend then looking into getting the Coober ECU mod and see what comes if it. Hopefully this takes care of the issue.
Very interested to see if it solves the problem. Do you need to do any other modifications (air filter box? exhaust?) or programing when adding the Coober ECU?
 
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