DCT gear box issue - honda NC750x

[Guest Bazinga]

Hi All

 

I'm new to the forum and not sure whether this has been already discussed but really hoping someone can help.

 

I have NC750X DCT 2013 that has been running super smoothly since I bought it (currently 32k miles done) until recently it developed a jerking issue when changing gears. There are actually 3 issues I've been experiencing. They're not happening all the time but at least twice a day every single day:

 

1. jerking movement when changing from 2nd to 1st gear. this happens in D, S and manual setting. Most of the time when I'm slowing down the change from 2nd to 1st gear would happen at around 11mph, occasionally the speed is already 11mph, then the jerking starts for few seconds until the speed gets to 9 or 8mph and that's when the gear would change to 1st.

 

2. when accelerating from full stop (either in D, S or manual) the bike stays in 1st gear and won't change up at all until I release acceleration a little bit. This issue is more common than the jerking movement. I understand that if you accelerate faster the bike will keep that gear for a bit longer if in D or S mode, but even when I'm in manual, flipping the gear up doesn't do anything until I release acceleration a bit.

 

3. slow response to gear changes. this mainly happens in Manual mode but occasionally also in D. I've always experienced a little bit delay in gear changes when the engine is cold, but after 3 minutes every gear was working again super smoothly. Now this issue happens even when the engine is hot. Sometimes there is a 3 seconds delay when trying to change the gear up or down.

 

I have searched the net for any related article but no luck. I've already done the DCT reset but that didn't make any difference. This is not service related as I actually had my 32k service done a month after those issues developed.

 

I have had though my chain and both sprockets replaced 1 month before 32k service and this is exactly when the gear box issues started. I have checked the chain length and rear sprocket (39T as per manual) just to make sure the mechanic put the correct one. Can't see the front sprocket but kind of trust him he put the right one. we both confirmed what he needs using NC manual before he ordered the parts. Could the chain and sprocket change be somehow related or just a pure coincidence?

 

I really hope you guys can help.

 

 

Thanks

[Guest machinman]

It definitly points towards the front sprocket, should be 17t.

Fingers crossed!!

[embee 7,288]

33 minutes ago, Bazinga said:

Hi All

………………………..

I have had though my chain and both sprockets replaced 1 month before 32k service and this is exactly when the gear box issues started. I have checked the chain length and rear sprocket (39T as per manual) just to make sure the mechanic put the correct one. Can't see the front sprocket but kind of trust him he put the right one. we both confirmed what he needs using NC manual before he ordered the parts. Could the chain and sprocket change be somehow related or just a pure coincidence?

 

First rule of any problem solving …………………… look at what was done just before the problem started. If all this had gradually got worse over a long time it would be a real headache to get to the bottom of it, if it started immediately after work was done then that points a finger.

It'd be a good guess to suspect the gearbox sprocket may be the wrong one. The 700 used a 16T and the 750 used a 17T. I don't know what effect that might have on the control system but before anything else at least eliminate this. 

I'm guessing you don't get any DCT system faults indicated in the display (bar across the middle flashing etc).

Have you checked the oil level?

The DCT has a temperature sensor (12) in the oil to accommodate the different characteristics as the oil gets hot. Check the connector on this for a start, it's in the vicinity of the gearbox sprocket so not impossible for this to be disturbed when doing work there.

 

 

Check the connector for the gear shift motor (6), also down near the g/box sprocket cover, and the angle sensor (7) which also sits there. Connectors down there can get oil/gunge from the chain on them. Clean inside the connectors with contact cleaner preferably, or WD40 at a push.

https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/NC/2014/NC750XDE/Engine/REDUCTION-CASE/71541/E_19/1/19298

Edited August 3, 2018 by embee

[maoleoin 12]

Definitely the front sprocket, I had a mechanic fit the wrong one, and accelerating it would hold gear until released just as you described. I only realised the problem when accelerating hard to join motorway after dawdling through city and A road traffic. Cue an argument with mechanic who has never seen my bike again once I got the sprocket replaced. The excuse was that the parts catalogue was wrong, and a lot of them are, but I think that a decent mechanic should have spotted the different size and queried it.  

 

Good luck with getting it sorted and do a reset after you do.

[Guest Bazinga]

Wow. Thanks guys for very quick response. So glad to know there are bikers there with great wisdom to share (unlike me).

 

I will definitely take it back now to the mechanic and ask him to show me the front sprocket (thanks machinman and maoleoin). All I did was told him exactly what parts I need assuming that he would order right parts.

 

If the sprocket is correct I will give him all the instructions provided by embee (thanks a lot).

 

I really appreciate it guys. I will get back to you with an update once investigated.

 

 

[Guest machinman]

Cool, keep us posted.

[embee 7,288]

It'll be interesting if indeed it is the gearbox sprocket teeth count on yours, as maoleoin described on his sounds exactly the same symptoms. This would indicate that the DCT does indeed use the wheel speed (ABS sensor) as well as the gearbox shaft speeds.

The bike road speed uses a sensor in the gearbox to send signals to the dash, and the DCT has speed sensors on the gearbox shafts. These would all correlate correctly regardless of the final drive gearing, it's only the wheel speed which would be wrong, and it's only the ABS pick-up which can detect this. Interesting.

[SteveThackery 3,090]

8 hours ago, embee said:

The bike road speed uses a sensor in the gearbox to send signals to the dash, and the DCT has speed sensors on the gearbox shafts. These would all correlate correctly regardless of the final drive gearing, it's only the wheel speed which would be wrong, and it's only the ABS pick-up which can detect this. Interesting.

 

That's why I'm still slightly sceptical that changing the sprocket can cause this.  (Mind you, absolutely happy to be proved wrong - it's a good way of learning stuff.)  It's hard to believe that the DCT would monitor the ABS sensors as well as the gearbox shafts.

 

Still, if it really is the case, then it could be tested by swapping the sprocket back and forth to confirm that the fault comes and goes reliably.

 

Edited August 3, 2018 by SteveThackery

[Guest Bazinga]

Hello All

 

I went to see the mechanic last weekend and we confirmed that the front (17T) and rear (39T) sprockets are correct as per manual. We have also looked at all connectors (mentioned by embee in the post above) - all clean, like new.

 

We've noticed though that the chain is very stiff so re-adjusted it with me sitting on the bike. (when previously adjusted while on side stand the chain looked fine but as soon as I sat on the bike it went stiff). We thought maybe somehow this could affect gear changes. Unfortunately not. When I went riding the next day I experienced the same gear box issues as previously : (

 

can you think of any other suggestions as what may be the issue?

 

 

Thanks in advance

 

[embee 7,288]

OK, absolutely basic stuff then.

What is the oil level? Check when warm, engine stopped for a couple of minutes, bike held upright, dipstick resting on the threads NOT screwed in, should be between the marks.

What oil is it using?

When was it last changed?

 

Have you checked the battery terminals are tight? Sounds silly but loose terminals can upset the voltage which the system might not like. Probably not this though. Is the bttery in good condition and is the charging voltage about right (something like 14V, under 13 or over 15 is out of spec.).

Check the condition of the big common earth terminal bolt on the frame just at the front left of the rider's seat. There are about a dozen earth wires coming to this point.

 

If all this is OK, next step I'd do is a DCT clutch initialisation. This is free, you can do it yourself, just follow the instructions TO THE LETTER, the engine must be hot when you do it. It's probably nothing whatsoever to do with anything, but it's free and takes a few minutes.

 

Check the condition of the connectors to the handlebar switch assemblies. They are located about 18" or so down the cables coming from the switchgear. I had a problem with tarnished pins in one of mine.

 

Check the condition of the connector on the back of the instrument pack (dashboard). These have been known to get poor connections and it can upset various things.

 

Next thing I'd check if I had to is the state of the shift motor and gear train (as in the parts diagram earlier). I've not heard of shift motors failing but I suppose there's always a first. You'd need a new paper gasket for the gearcase, which are stupid money, as it will very probably stick to the surfaces and break up when you take it off.

 

I'm still taking it that you don't get any check engine (MIL) light or get a bar flashing in the gear shift window?

[SteveThackery 3,090]

To add to Murray's suggestions: I think this is a hydraulic issue where one of the clutches is slow to engage. I would change out the oil and the DCT filter, using a good quality 10W-30 JASO-certified oil.  Do not use a 10W-40 - it won't hurt the engine but it's too thick for the DCT gearbox.

 

I would do this myself, regardless of when it was last changed, unless you changed it yourself and can guarantee that it's got the correct 10W-30 oil in it and a new DCT oil filter.  If a dealer did it, you can't trust what it says on the invoice.  It may not fix it, but at least you'll have eliminated that as a possible cause.

 

Obviously add this to the list Murray gives above - not instead of.  

[embee 7,288]

Checking/changing the DCT filter is a good shout. If that's clogged for some reason (not being changed?) it will upset the clutch engagement.

[Guest Bazinga]

Thank you embee and Steve for more suggestions. Apologies for not being responsive, I was away with a very limited access to internet.

 

To answer embee's previous questions: There is no 'check engine' light and I've done DCT initialisation few times already, which didn't make any difference.

 

Additional issue also cam to light last week. When initially the few seconds delay was happening from 1st to 2nd gear and 4th to 5th, now it started happening from N to 1st gear. I was basically waiting on red light with N engaged, then when green light came on I flipped the switch to D, I heard when the 1st gear became engaged (gearbox noise) but when I rev'd the bike did not move, 2 seconds later the 1st gear appeared on the panel, I rev'd and it then moved. a bit annoying especially when you try to leave the traffic lights before all the cars do.

 

In regards to the engine oil being the incorrect one, I had the oil changed (at least I hope I did) when I had my service done at 24k miles and there were no gear changes issues until 31K  - that's 7k miles without any issues, not a single one. But maybe the oil was never changed at 24k, or the filters. I tend to do my service at the 'John's of Romford honda'. I did my previous and latest (32k) services at the same place, so if they haven't changed it last time I would expect them to change it this time. To be clear the 32k service was done about 1 month after the gearbox issues have started, so at least I'm sure that those issues were not caused by the actual service.

 

Nevertheless, I will try every single of all your suggestions anyway (oil, filter, connectors, etc.) either this or next weekend, and I will keep you updated.

 

Thanks again for the advice. I really appreciate it.

[embee 7,288]

I'm wondering from what you describe whether it's the shift motor/reduction case gears moving slowly. Definitely worth a look in there if the problem is getting worse. If it is actually selecting the gears but doing it very slowly it could explain the over-revving, also the delay in being able to drive away after selecting 1st. I would guess the motor/selector has to return to the central position before the system will instruct the clutches to engage. Sometimes with electronickery systems it can still be the "nuts and bolts" which let it down.

[SteveThackery 3,090]

17 hours ago, embee said:

I'm wondering from what you describe whether it's the shift motor/reduction case gears moving slowly. Definitely worth a look in there if the problem is getting worse. If it is actually selecting the gears but doing it very slowly it could explain the over-revving, also the delay in being able to drive away after selecting 1st. I would guess the motor/selector has to return to the central position before the system will instruct the clutches to engage. Sometimes with electronickery systems it can still be the "nuts and bolts" which let it down.

 

Yes.  It is beginning to sound like it will need a proper investigation.  The challenge will by finding a mechanic who knows what they are doing.