If your lights are dimming its due to voltage drop. Due to a drain which the circuit can't support or a bad earth. Try it with the engine running.

Some USB devices can perhaps pull more juice than KTM intended.

I'm not sure it's that. This happened when it was plugged that one time and ever since even when nothing is plugged in.

The time display disappearing is just weird too, I mean why not the odometer or trip readings too as they all display in the same part of the screen

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Gremlins. You need an exorcist.

My money's on aliens

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If it is doing this permanently rather than intermittantly, then possibly age related.
Car instrument panels can show similar symptoms; IIRC, some Nissans had a habit of losing the digital clock display or parts of the electronic numeral display(s).

TPS? Wow, forget your bike had one! Hope it's the source of the problem!

IIRC, KTM instrument clusters are KNOWN to go bad for no obvious reason. So you may be on the hook for a new one and I believe they are very expensive.
:(

If you remove it ... you risk messing with wiring and screwing up CDI as a lot of the wiring goes through the CDI, so I'm not sure you can just unplug it and throw it in the bin ... but there may be a way, if you know how.

If the cluster has gotten WET ... you may try drying it slowly in the Sun (FACE DOWN!) for couple days. Never face LED display directly into Sun ... this will ruin it for sure ... and that could be what's happened to yours. :oops2:

Good Luck! :D

yeah, but it can't be a coincidence that both things (screen fade / disappearing clock) happened at same time as using the accessory power socket for the first time. I read somewhere that a fuse could have gone or that there might even be a watch battery somewhere on the cluster for the clock but not convinced has haven't seen anything in the manual about that. Will check the fuses though.

Incidentally the clock DOES reappear if I hold both the Mode and Set buttons while ignition off, then turn on again. I can reset the clock and it works fine while I'm riding but it goes away again next time I turn off lol.

It's definitely running better, much more lively than it was. Will keep monitoring and will check what the fuel consumption is doing. Hoping it was just a combination of all these things plus $hitty maintenance from the previous owner (not forgetting the incompetent work from the KTM mechanic..)

[QUOTE=mollydog;525951]TPS? Wow, forget your bike had one! Hope it's the source of the problem!]

The early technology used in digital displays is possibly at the heart of the issue.
+ you don't know the history of the machine - for instance, water entering the display could have short circuited some of the electronic "mother board".

Certainly, we are talking herein about electronics, not electrickery.
Computer mother boards have built in "button batteries" (that maintain memory functions while not powered up by any other means) and modern CANbus machines that have ECUs may also contain such technology; I doubt that the 640 has this and your handbook doesn't mention such?

I had a 2008 990 that has the same "Tonka toy orange" display and never had issues with that; I also had a 2003 Nissan car which had part of the digital display missing especially within the clock digits; some of the latter worked and some did not. There were other things of more importance however.

Well clock issue is formally resolved - found 2 blown 10A fuses (no 2 & 5). Works fine now :) - all fuses were checked a while ago though so guess something blew when the accessory socket was used

I took the opportunity to check the sprocket sizes today as have been meaning to make sure they are standard - but interestingly they're actually 40T / 16T. The rear should be 42T right? Its not in great condition (the front is totally fine though..) so will replace with a 42. Any ideas how the 40/16 combo would affect the performance?

You need to check the tech specs for the original information for the bike.

A bigger number of teeth at the back will lower the gearing overall, for increased acceleration and lower top speed, all else remaining the same.
Your existing combination is vice versa.

Great news on the dash display! :thumbup1: Easy, simple fix!

I'd look up standard sprocket sizes and go with that to start. 16T front sprocket seems BIG to me. If you cruise highway over 70 mph a lot then maybe OK, but for general riding, light trail riding, lower gearing will feel stronger with crisper acceleration.

15T/42T may be the way to go. Remember, one T change at front equals "around" 3 T at the rear. So sounds like your bike was geared quite HIGH.

Less vibes may be why PO did this, as your bike has some of the worst vibes of any bike I've ever owned (over 50) ... although my Duke ll was really not bad. (Man, wish I'd not sold that one! doh)

KTM rep said the Duke's dual exhaust calms vibes. No idea how he came up with that. But compared to my 640 dual sport, the Duke felt like a Lexus.
bier

If replacing fuses brings the clock back then you likely have a short in the system... Most likely areas to check are the cluster wrap harness of wires that are zip tied to the dash support bar and the wires that run to to the accessory outlet... Check the wires where they bend as they come out of the harness for abrasions to the shielding and check that they have not rubbed raw against the dash bar... Check the wires for the same where they go to the cluster plugs on the right side dash support strut... Another thing to check is the soldered terminals inside the ignition keyswitch as they will sometimes pop loose and cause erratic electrical problems.. To get at the keyswitch you have to remove the base by taking out the 2 phillips head screws and then pry and pop the base apart as it is a slip fit plastic sleeve.. Once apart you will be able to see if any terminals are broken and resolder them back to their posts...

I still have all the original electrical components on my bike at 210,000+ km but have had to fix worn wires and such on several occasions... Sometimes the buttons stop working on the speedo.. When that happens I remove the faceplate and spray electro contact cleaner in at the same time working the buttons, this bit of a wash always restores the function of the buttons..

16/42 with a 110 link chain is the OEM standard gearing for this bike and works well for all around riding... A lot of guys that do a bit more technical riding will go with the 15/42 that Mollydog mentioned... As KTM uses flip around axle adjuster blocks you can drop 2 teeth on the countershaft or rear sprocket without having to shorten the chain... A word of warning, do not buy the OEM aluminum sprockets, they are crap and last about 7000 KM... Instead ask for the KTM steel sprockets which last 3 times longer or go with aftermarket steel sprockets...

I run 17/45 or 17/44 on my bikes which is close to stock gearing but allows a slightly bigger bend radius to the chain giving it a little longer lifespan.. With the bigger bend radius the chain also rubs a slight bit less on the rub block so that lasts longer too... This gearing requires a 112 link chain... I run this gearing all the time for all types of riding, in the real tight tough stuff slipping the clutch is my low gear...

That is good strategy to extend chain/sprocket and rubbing block life! :thumbup1:

On some bikes its hard to go with a BIG front sprocket because of clearance issues. (DR650) I can go up ONE T but no more. Going to a tiny front sprocket to achieve lower gearing also has it's problems (i.e. rapid front sprocket wear, rubbing block wear)

The beauty of your set up is if you get into technical conditions you can simply pull over the put on a 15T front sprocket. 10 minutes later you've got Mountain Goat low gearing! bier

Quality aftermarket sprockets are the way to go to save a few bucks.
JT sprockets (Thailand) are pretty good in my experience, nearly as good as OEM. As said, Steel only!