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670cc

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If you adjusted the chain slack after the chain fell off the first time, then the chain fell off again, I suggest you stop riding the motorcycle and take it to a qualified mechanic for service. I suspect you are not following proper procedures, and I also worry you may not be using a torque wrench to properly tighten fasteners.

Drive chains falling off is an extremely uncommon event, and could put you in an unsafe situation.
 

TacomaJD

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If you adjusted the chain slack after the chain fell off the first time, then the chain fell off again, I suggest you stop riding the motorcycle and take it to a qualified mechanic for service. I suspect you are not following proper procedures, and I also worry you may not be using a torque wrench to properly tighten fasteners.

Drive chains falling off is an extremely uncommon event, and could put you in an unsafe situation.
100% agree. Carry it to someone that knows what they're doing before you get hurt.
 

lootzyan

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...Leave the battery disconnected overnight and see if it resets. ...
I have heard this "reset theory" over and over again and still wonder how someone might come up with such an idea? Reset consists in sending an internal instruction in an electronic device to return to the initial state according to program recommendation. How can this be done if the main source of electricity is disconnected? Some electronic devices have an internal battery, but I can assure you that NC's ECM/PCM do not. Without electricity, the ECM is as dumb as a brick.
 

mzflorida

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I have heard this "reset theory" over and over again and still wonder how someone might come up with such an idea? Reset consists in sending an internal instruction in an electronic device to return to the initial state according to program recommendation. How can this be done if the main source of electricity is disconnected? Some electronic devices have an internal battery, but I can assure you that NC's ECM/PCM do not. Without electricity, the ECM is as dumb as a brick.

I see how you could apply that logic and you're not necessarily wrong. I don't know if this is the case for the NC, but many chipsets have a preprogrammed function called a power on reset. If you ever had a laptop fault, had to remove your battery, then press and hold the power button as part of the troubleshooting process you performed a power on reset. When you restored power by replacing the battery and pressing the start button you told the laptop to check for faults in the program, write the correct instructions, if possible, detect faults and report any to the user, or start up and start performing. Some power on resets requires a complete absence of power, others run automatically every time the "on" switch is used. So the ECM may not have its processing ability when power is absent, but it still has its instructions that may force self-correcting functions after an absence of power. Depends on the chip, the application, etc. I have zero clue if the NC has that type of chip or program.

EDIT Brief version: The chip, after an absence of power, presumes that its program or programs caused the absence of power and has the ability to quickly rewrite the instructions upon power being restored.
 
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shinøbigami

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I’m having it towed to the dealership next week, I’m just trying to get it home, it’s a heavy bike and I live up a hill about 2 miles away from where it broke down and I already pushed it as far as I could, about a mile and a half. I’m sorry but I’m not paying $250 for a tow 2 miles away :(
 

showkey

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Think the disconnect the battery got started years back with OBD1 and OBDII cars and trucks. For many years the error codes would be erased or cleared with a power disconnect.
So common trick was ……disconnect the battery just before emissions testing to clear all the problems that would cause a test failure. EPA regulators figured this out and mandated that codes be stored on power down and only cleared by a scan tool or ECM clearing process as mentioned in the shop manual. Also modern cars need to actually run the emissions readiness tests to pass. This means the car has to driven some distance under very specific parameters to run all the readiness tests. Readiness test could be renamed self tests that prove the any specific system like EGR, misfire, EVAP is working.

So modern motorcycles followed with codes that do no clear with power down.
 

zo10000

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Hi
Maybe it's a bit late for this reply, but normally when the engine stops for whatever reason and you're in a high gear, it won't be able to come back to the 1st gear only you start to rotate the gears in the gearbox. This means that after you put up the chain you turn the ignition on, turn the kill switch to on and rotate the wheel until it goes back to the 1st gear.

Hope it helps you in the future.

Cheers!
Hey there, today my chain flew off the rear sprocket, it’s the 2nd time this has happened. The first time was about a week ago, immediately pulled over and shut off the bike, put on center stand and was able to manually rotate tire and reinstall the chain. Started her up and slowly coasted home, once I got home I adjusted the slack (which ended up being at max) and everything was back to normal. Sprockets look fine still but I’ll be honest, I never adjusted the chain before (new to motorcycling and learning maintenance as I go), so I’ve ordered a new chain. Anyways, as I’m waiting on the new chain, I’m still riding it as it’s my daily commuter and the chain fell off again, I’m going maybe 30mph but uphill this time. Repeat the same process and get the chain back on, however, this time the bike won’t start. In the display there’s a blinking line ( - ) where it would normally show what gear it’s in. No crank, no nothing with ignition on and holding brake and pressing starter. Anyone know of a way to reset the ECU on the DCT models? I’ve disconnected the battery for about an hour and still the same display and no response when I try to start it. The bike is a 2021 NC750XD with about 12k miles. Thanks in advance for any rep
 
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