Showing RPMs too high

[moguster 9]

Hi,

 

Recently bought NC750S 2015.

And just now noticed that dashboard shows way too high RPMs than it really is.

Is there a way how to calibrate it? Or any other solution available?

[Xactly 5,501]

An interesting one; I don't recall that issue arising with an NC.

I used to have a Moto Guzzi. One evening I started the engine and rode off and was alarmed to discover that the engine appeared to be revving much higher than usual (about double) according to the rev counter, yet the clutch was not slipping nor did the engine appear to be running faster than normal in any gear. Weird. 

It turned out to be that on switching the ignition on I had started the engine a little bit too soon, so that the ECU diagnostics had not completed the self-test before the engine was started.

The rev counter needle on that bike has no stops at either end. As the diagnostics had not completed the needle range had not been calibrated, hence the fast reading and slow needle reaction to changes in revs.

The cure was simply to ensure that next time the bike was used the diagnostics should be allowed to complete. Simple solution.

Obviously on the NC there is no needle as the rev counter is not an analogue display, but it is possible that the same calibration procedure needs to be followed - just a guess really. 

I suggest you try disconnecting the battery for a while, reconnect it then ensure that the diagnostics complete before starting the engine. It might work; it might not but in that case I don't know what else to suggest.

Do let us know what happens.

[elbee 754]

Once on my ER-6N I rode through a colossal downpour and for about a week afterwards the rev counter was all over the place. After about a week some sensor or contact finally dried out and all was fine.

[Dan German 896]

Out of curiosity, how are you measuring the “correct” rpm, and over what range?

[moguster 9]

6 hours ago, Dan German said:

Out of curiosity, how are you measuring the “correct” rpm, and over what range?

For example: when engine is in working temperature - it shows ~2500rpm, driving at 60km/h in 5th gear it shows 7000rpm. And i it allows to rev way more even it is reaching scale limit.

Motorcycle had small crash and I'm wondering maybe one of sensors is not in correct position, or something similar...

[moguster 9]

BTW does 2015 NC750SA should show gear in the dash? Asking because it doesn't show

[jeremyr62 2,605]

Are the front and rear sprockets the correct size? Yes think it should show the gear selected. Is the SA a DCT or manual?

[moguster 9]

7 hours ago, jeremyr62 said:

Are the front and rear sprockets the correct size? Yes think it should show the gear selected. Is the SA a DCT or manual?

Sprockets sizes are correct. It is manual.

Showing too high rpms not only when driving, but also when standing.

[moguster 9]

23 hours ago, Xactly said:

An interesting one; I don't recall that issue arising with an NC.

I used to have a Moto Guzzi. One evening I started the engine and rode off and was alarmed to discover that the engine appeared to be revving much higher than usual (about double) according to the rev counter, yet the clutch was not slipping nor did the engine appear to be running faster than normal in any gear. Weird. 

It turned out to be that on switching the ignition on I had started the engine a little bit too soon, so that the ECU diagnostics had not completed the self-test before the engine was started.

The rev counter needle on that bike has no stops at either end. As the diagnostics had not completed the needle range had not been calibrated, hence the fast reading and slow needle reaction to changes in revs.

The cure was simply to ensure that next time the bike was used the diagnostics should be allowed to complete. Simple solution.

Obviously on the NC there is no needle as the rev counter is not an analogue display, but it is possible that the same calibration procedure needs to be followed - just a guess really. 

I suggest you try disconnecting the battery for a while, reconnect it then ensure that the diagnostics complete before starting the engine. It might work; it might not but in that case I don't know what else to suggest.

Do let us know what happens.

Tried to disconnect battery, wait for 10 minutes and then connect...

Same issue...

[Slowboy 20,658]

Either sensor failing or a plug somewhere is not properly seated or dirty. Also worth checking the multi plug at the back of the instrument panel as that can corrode and cause odd effects.

 

interesting the Engine management light isn’t being triggered by an out of spec reading. I would be tempted to look at the instrument panel multi plug first.

 

A lot of body panels to strip off to get to it if I recall correctly.

[moguster 9]

4 hours ago, Slowboy said:

Either sensor failing or a plug somewhere is not properly seated or dirty. Also worth checking the multi plug at the back of the instrument panel as that can corrode and cause odd effects.

 

interesting the Engine management light isn’t being triggered by an out of spec reading. I would be tempted to look at the instrument panel multi plug first.

 

A lot of body panels to strip off to get to it if I recall correctly.

Thanks for advice, will check back of instrument panel.

[moguster 9]

4 hours ago, moguster said:

Thanks for advice, will check back of instrument panel.

Checked the multiplug, all contacts clean, connected firmly... anyone knows where is the other end of all these wires? Probably goes to the ecu, but where it is located?

[Xactly 5,501]

11 hours ago, moguster said:

Tried to disconnect battery, wait for 10 minutes and then connect...

Same issue...

OK; it was a bit of a longshot.

[MatBin 5,115]

1 hour ago, Xactly said:

OK; it was a bit of a longshot.

Hmmm, I wonder if it could be a battery issue, 2015 bike, original battery?

[moguster 9]

6 hours ago, MatBin said:

Hmmm, I wonder if it could be a battery issue, 2015 bike, original battery?

No, it is new battery

[EdG 72]

How much time and money do you want to spend?  Does the bike run OK?  If it does, ignore the display and enjoy the ride.

[Andy m 23,762]

The sensor is mounted somewhere on the crank, so base of the cylinder/clutch sort of area. 

 

It's an inductance type sensor so unlikely to read wrong, they either back off and read nothing or go open circuit. Follow the cable though, any sign of crushing damage? An intermittent short to another sensor will occasionally cause double speeding.

 

I'm also surprised the EM light isn't on, the display is just bling, the real purpose of the sensor is fuelling. What's the fuel consumption like? If it's doing 35mpg it could be something mechanical like the clutch.

 

An OBD reading of the measured RPM against a laser tach on the rotor or whatever is accessible on the crank end would tell you which side of the ECU the problem was.

 

The lack of GPI makes me want to follow the cable engine to ECU.

 

What was the damage when crashed? These sensors are amazingly tough, I've never known one fail due to a crash and known a few survive fires. It's mounted so deep it's unlikely to have seen any impact. The loom is far more likely. Buzz every core to every other, no double connections allowed.

 

The Guzzi mentioned is a different animal in that it includes the worlds shortest and most pointless CANbus. Computers wake up at their own pace. This is analogue, so just works. Guzzi saved a whole 18-inches of 12-core by going CAN ECU to display 😖

 

Andy

[Xactly 5,501]

1 hour ago, Andy m said:

The sensor is mounted somewhere on the crank, so base of the cylinder/clutch sort of area. 

 

It's an inductance type sensor so unlikely to read wrong, they either back off and read nothing or go open circuit. Follow the cable though, any sign of crushing damage? An intermittent short to another sensor will occasionally cause double speeding.

 

I'm also surprised the EM light isn't on, the display is just bling, the real purpose of the sensor is fuelling. What's the fuel consumption like? If it's doing 35mpg it could be something mechanical like the clutch.

 

An OBD reading of the measured RPM against a laser tach on the rotor or whatever is accessible on the crank end would tell you which side of the ECU the problem was.

 

The lack of GPI makes me want to follow the cable engine to ECU.

 

What was the damage when crashed? These sensors are amazingly tough, I've never known one fail due to a crash and known a few survive fires. It's mounted so deep it's unlikely to have seen any impact. The loom is far more likely. Buzz every core to every other, no double connections allowed.

 

The Guzzi mentioned is a different animal in that it includes the worlds shortest and most pointless CANbus. Computers wake up at their own pace. This is analogue, so just works. Guzzi saved a whole 18-inches of 12-core by going CAN ECU to display 😖

 

Andy

The honour of having the world's shortest and most pointless CANbus is shared by the (I think) last two years of the 865 Triumph twins. The two instruments on my Thruxton - speedo and rev counter were CANbus. Never made much sense to me.

[moguster 9]

Ok, found the issue...

Looks like this motorcycle had issue and someone replaced it's ECU...

And the ECU that is inserted now - is from NC700X. That's why it also does not show selected gear and fuel consumption...

Current ECU code: 38770-MGS-D11

[Andy m 23,762]

That'll do it! Glad you found it. 👍

 

Anything in the history to suggest it was stolen? ECU replacement is often after some scrote shoved a soldering iron through the case to defeat the HISS. Welding will do it too.

 

Andy

[Skidt 1,333]

Likewise, glad you’ve got to the bottom of it. 👍 

[moguster 9]

7 minutes ago, Andy m said:

That'll do it! Glad you found it. 👍

 

Anything in the history to suggest it was stolen? ECU replacement is often after some scrote shoved a soldering iron through the case to defeat the HISS. Welding will do it too.

 

Andy

History is clean, doesn't look like it was stolen.

Interesting if I will change the ECU to a correct one. How it would be with the key?

[Andy m 23,762]

15 minutes ago, moguster said:

. How it would be with the key?

The new ECU needs programming to match the key, otherwise it thinks you are using another bike's key to steal it and activates the immobiliser. Usually a HONDA dealer job because they have the access via their diagnostics.

 

Andy

[jeremyr62 2,605]

I’m just amazed it worked at all. 

[Xactly 5,501]

Glad you found the culprit.