Need Help DCT acting weird

GabrielCS

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Hi guys,

I own a NC750X 2017 which I've been happily riding so far.

A problem occurred recently with my DCT: it won't at times go into drive when it's in neutral or in neutral when it is in drive (I'm not reving it).
For example, this may occur when I stop at a red light and the bike is still trying to go with the brakes pressed, if I press the N button many times it may go intro neutral but if it does it wont easily go back into Drive.

This occurred after this winter I was caught by surprise by a winter storm and had to deposit my bike with a quarter of a tank filled (I know, bad). It stayed on that tank for about 2 whole months.
When I tried starting it the bike was exhausting short burst of smoke and could not properly start (it would just turn off). I thought ok, needs new fuel.
I refuelled it and after a while the engine started working as usual. I also changed the oil afterwards but the problems appeared before that.

I stumbled upon a DCT reset while trying to fix this, it seems to help but won't last for long.

I would really appreciate any advice here as I'm stuck. Other than that the bike seems to function perfectly well ( gear changes also).
 

TacomaJD

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I wouldn't think storing for 2 months would really be long enough even with 1/4 tank of gas to cause problems running. Strange. I've let bikes sit that long at times without cranking, not even on a tender, fire right up and run without issue.

Ditto on the battery, maybe it dropped voltage over the storage period and either needs a good trickle charge or replaced?
 

670cc

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Have you checked your battery as a. Low battery can cause DCT problems.
Rocker66. Now there's a name I haven't seen in a while. Welcome back!
 

GabrielCS

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Sry for late reply.
I got back on the bike recently as I abandoned it cause of bad weather.

I don't think it's the battery as it starts easily. I seem to have the DCT problem every time I get on the bike, but along with the warmer temperatures the bikes seems to respond more "normally".
It still gets stuck in D or N but not as often.

I'll be getting it at a dealers next week, I hope they can sort it out. I'll post here if I find out anything new.
 

Madison Sully

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When I had a Can Am Spyder with auto transmission (paddle switches), it had problems that ultimately were due to the transmission oil filter being slightly blocked. Not enough oil pressure to change gears, apparently. Due to this experience, any time I change oil on my NC700 DCT I change the transmission filter too.
 

Doc True

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Sry for late reply.
I got back on the bike recently as I abandoned it cause of bad weather.

I don't think it's the battery as it starts easily. I seem to have the DCT problem every time I get on the bike, but along with the warmer temperatures the bikes seems to respond more "normally".
It still gets stuck in D or N but not as often.

I'll be getting it at a dealers next week, I hope they can sort it out. I'll post here if I find out anything new.
The transmissions on these bikes are overly sensitive to voltage drops. The voltage in the battery may be too low to operate the transmission even if the bike starts normally. It's very common. I would replace the battery before I took it to a mechanic if it were my bike.
 

lootzyan

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... I would replace the battery before I took it to a mechanic if it were my bike...
Please, do not confuse unnecessarily. When the engine is running, the alternator provides 100% electricity. The battery is being charged during this time, so it cannot affect the operation of DCT or other electrical components.
 

lootzyan

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...this may occur when I stop at a red light and the bike is still trying to go with the brakes pressed, if I press the N button many times it may go intro neutral but if it does it wont easily go back into Drive...
This can happen if the engine idle speed is too high. Have you not noticed a deviation in engine idle speed? Check correct throttle operation, PGM-FI. This is important for proper DCT clutch operation. Also faulty operation of DCT clutch engagement is possible.
 

HarveyM

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Sometimes a clutch calibration helps. See here-


At least it's something you can do before the dealer sees it.
 

GabrielCS

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I just went to the Honda dealer yesterday, they said it might be because of the DCT sensors (it has 3 on the right side, next to the DCT filter cover).
I went on and explained it happened all of a sudden after getting the bike out of the garage and that the problem tends to go away with warmer weather.

They then suggested, rather than opening everything up, doing an oil change and seeing if that would help. So they changed the filters and oil and afterwards performed a "re-learn of the speeds by the DCT" or something like that.

Afterwards the speed change felt a lot better, and the bike seemed to still have the problem but not as bad: it would still pull me sometimes when stopping at traffic lights, but as soon as I would hit the N button it would go into neutral, that did not happen before, and then if would press D it would go into drive. So the only problem it has right now it seems it that it still pulls me after a complete stop.

The dealer suggested I drive a few more hundred kms and see how it goes from there, they said it may be some junk left over from the last oil change and it may clear itself up (pretty weird as the oil was new, but they were "aftermarket" oil and filters).
 

lootzyan

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... it would still pull me sometimes when stopping at traffic lights...
Could they measure engine speed at such a moment? This is important for diagnosing the problem. In this way they could determine if the problem is faulty throttle operation or a problem with the clutch linear solenoid valve or clutch oil pressure. The clutch is still engaged. The clutch should disengage when the engine speed falls below approx. 1450 RPM. (They should know).
 

davidc83

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I just went to the Honda dealer yesterday, they said it might be because of the DCT sensors (it has 3 on the right side, next to the DCT filter cover).
I went on and explained it happened all of a sudden after getting the bike out of the garage and that the problem tends to go away with warmer weather.

They then suggested, rather than opening everything up, doing an oil change and seeing if that would help. So they changed the filters and oil and afterwards performed a "re-learn of the speeds by the DCT" or something like that.

Afterwards the speed change felt a lot better, and the bike seemed to still have the problem but not as bad: it would still pull me sometimes when stopping at traffic lights, but as soon as I would hit the N button it would go into neutral, that did not happen before, and then if would press D it would go into drive. So the only problem it has right now it seems it that it still pulls me after a complete stop.

The dealer suggested I drive a few more hundred kms and see how it goes from there, they said it may be some junk left over from the last oil change and it may clear itself up (pretty weird as the oil was new, but they were "aftermarket" oil and filters).
Sounds like the dealer did a DCT calibration as mentioned in a post above..... when the bike attempt to pulls you at a stop, have you noticed the RPMs increasing? If so, could be stuck throttle cable,,,either at the throttle or on the engine casing...
 

670cc

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Yes, as already mentioned, take note of the engine speed at idle and see if it is at the spec of around 1200 RPM and steady.

As for the dealer telling you it may be junk in the oil that may clear up later, they are just telling you something random in hopes you’ll go away and not bother them with a problem they don’t understand.
 

GabrielCS

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The RPM is higher if the bike pulls me, but I guess that's "normal" if the clutch is engaged, if I hit N when the bike is pulling, RPM drops suddenly.

As for the DCT learning thing I don't know if the dealer performed the usual DCT calibration as mentioned above, will ask next time I'm there. I did do it a couple times before myself, but with limited success (it would be better then after a while get worse).

Now I thought the exact thing when they said there was some junk or whatever in the old oil (that they were BS-ing me), but after I rode for 10 km it did feel a lot better (even if the bike pulled at a stop I could press N and it actually worked, then I could press D and that also worked).

I will keep you guys updated with how thing evolve; unfortunately due to pandemic lockdown I can't ride that much.
 

670cc

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The RPM is higher if the bike pulls me, but I guess that's "normal" if the clutch is engaged, if I hit N when the bike is pulling, RPM drops suddenly.

As for the DCT learning thing I don't know if the dealer performed the usual DCT calibration as mentioned above, will ask next time I'm there. I did do it a couple times before myself, but with limited success (it would be better then after a while get worse).

Now I thought the exact thing when they said there was some junk or whatever in the old oil (that they were BS-ing me), but after I rode for 10 km it did feel a lot better (even if the bike pulled at a stop I could press N and it actually worked, then I could press D and that also worked).

I will keep you guys updated with how thing evolve; unfortunately due to pandemic lockdown I can't ride that much.
The idle RPM being higher when the “bike pulls” you doesn't seem normal. The clutch engaging shouldn’t increase the RPM, rather I think the RPM increasing engages the clutch. Perhaps the clutch is engaging because the idle RPM is advancing due to problem with the bike‘s idle control. We have had a few cases reported where the idle control unit has behaved erratically. Since RPM drops suddenly when you go to N, it doesn’t sound like a tight throttle cable is causing it.

Keep us posted.
 

lootzyan

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No, this is not "normal". Clutch must be disengaged at idle RPM.
Just like in a simple CVT transmission (small scooters mostly), where the pulleys/clutch engagement/disengagement is mechanical, depending on the engine's RPM, in this DCT transmission the clutch engagement/disengagement is hydraulic, through the linear solenoid valve, controlled by PCM.

(I did not notice that I repeat after 670cc)
 

GabrielCS

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Update:
The bike seems to be running better the more I ride it (i.e. the number of odd dct misshaps per ride is going down). I have now experienced rides without it happening even once.
That being said the DCT still locks up after I accelerate heavily (with high revs), but the only effect is that it will pull me at a stop afterwards, as soon as I hit N it will go neutral.

Unfortunately, I'm still under 100 km ridden since I got it back as I work from home during the pandemic and don t get to go out much.
 

lootzyan

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Sorry to say, but chatting here in the forum will not help you much. What you need is an experienced, knowledgeable technician in an Honda authorized dealer workshop with Honda approved testing equipment. What happens to your NC is quite uncommon.
 
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