NT700V Engine cuts out below 3000 rpm

goldwingrider

Joined
Oct 22, 2015
Messages
10
Location
Billingham, England
My 2010 NT700V has developed a problem when hot, if you let the revs drop below about 3000 then the engine will quite often cut out and die, if I keep the revs above 3000 then it seems to run OK.
The MIL light does not come on when this happens.
I'm thinking the crank sensor might be failing??
 
Cheap and easy first ports of call are the spark plug caps (change to NGK) and also all the wiring connections in the area of the ECU (clean and reattach). Could also be the crank position sensor as you suggest but this is often accompanied by erratic starting as well. Do one thing at a time!! Happy hunting........
 
Tough one. Usually, ignition problems, unless having to do with mechanical advance, do not show up in this manner, ...if asking the bike if it has any codes stored isnt helpful, then I would just guess fuel. But I still wouldnt rule out ignition.
Certainly doesnt hurt to run the bike in a blacked out situation and look for arcing.
Does one plug look different than another?

I am no expert on spray patterns of old injectors. Maybe one has issues that are masked when the gas is flowing fast. Wild Arse guess.
 
I fitted new plug caps (NGK) and HT leads, spark plugs a couple of months ago so I they should be OK.
I fitted a new crank sensor today and the bike runs OK at tickover but I won't get a chance to ride it for a couple of days so I am just hoping that the new sensor has cured the problem !
 
goldwingrider said:
I fitted new plug caps (NGK) and HT leads, spark plugs a couple of months ago so I they should be OK.
I fitted a new crank sensor today and the bike runs OK at tickover but I won't get a chance to ride it for a couple of days so I am just hoping that the new sensor has cured the problem !
Click to expand...
I wonder what would happen if instead of opening up, a sensor shorts partway out? Not enough signal until higher crank speed?
 
goldwingrider said:
I finally got the chance to take the bike out for a ride today, about 140 miles on a mix of roads and it ran perfectly so it looks like the crank sensor was the problem.
Click to expand...
Interesting. I wonder if any of our Euro friends have experienced this? I am still liking my theory, barring any dirty connectors.
In an old magneto, the speed at which the magnet passes the coil determines the strength of the spark. Motorcycle or lawn mower.

In this case, if say 30 percent of the windings were shorted out, then the faster the engine turns, you get to a point where the generated pulse is large enough to work the system.

The only fly in my ointment is that the engine computer has historical memory. In other words, once the engine starts, the computer sees the relationship between the crank and cam position sensor. You could actually remove the crank position sensor once the engine is running.
That leads to an intriguing possibility. Suppose at low rpm, the sensor was sending out ghost signals? I got nothing. Let's hope yours stays fixed!
 
Might be interesting to have a good resistance/impedance reading of the old sensor and a new one. This would need the correct test equipment to do. Still may not show anything since it is kind of an intermittent failure.
This doesn't follow the common sensor failure mode of failure to start at a gas stop or other inconvenient location.

Arknt
 
ARKNT said:
Might be interesting to have a good resistance/impedance reading of the old sensor and a new one. This would need the correct test equipment to do. Still may not show anything since it is kind of an intermittent failure.
This doesn't follow the common sensor failure mode of failure to start at a gas stop or other inconvenient location.

Arknt
Click to expand...
Correct. Mine blew a code, and it followed the path that all bad sensors take...intermittantly open, which of course doesnt kill the engine...but the engine wont start till the sensor cools and re connects the break.
This is a failure for an SAE engineer to investigate. I have litterally fixed thousands of police two way radios. Portables and car radios and base stations, etc. We used to say there were only 10 things that broke on any given model of radio for 95 percent of the failures. It was those last 5 percent that were head shakers. Sometimes, we did things that fixed the problem, only we didnt know what we did...like accidently exersising the contacts of a conntector or module.....
 
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