My G650x-Challenge keeps blowing fuses (F) when starting hot.
New battery, all terminals and connections checked and cleaned, Starter relay and starter switch swapped from another XC with the same results.
Any ideas much appreciated

Unless you want to trace the wiring loom and find where its shorting out (i am guessing a wire is earthing somewhere) then you have to take it to a bike electrician and get him to find where.

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Shortcut could also be in the ignition lock.
Not so easy to borrow this from your friends bike, but worth a try.
Works only if there is no immobilizer in the locks!

An old trick is to connect a bulb instead of the fuse to the fuse-socket(T-connection).
The job for the bulb is to limit the electric power, so you can start your bike.
You are now able to check the cables (pressing, bending....), when your fingers find the fault, the bulb changes its brightness.
Darker means cable is ok now, brighter means shortcut.

Be carefull, bulb will get HOT

Good luck

This happened on mine after I added some bits, I forget what. It seemed to blow the headlight fuse every time I braked. My rear pads were low which confused the hell out of me how that could be related.
In the end it turned out to be the wiring loom running down the left side of the headstock into the frame. I must have pulled or trapped something and the wire had bared against the frame so every time I turned hard left (pulling in to park, etc) I was popping a fuse. It may be something as simple as that so if you've done any work check there first and look for all the obvious things, broken or frayed wires touching.
It was a daunting task for me and a hell of a relief when I found that was all it was.
F is diagnostic plug, starter relay and indicators, right? Have you checked you're using the right value fuse? I think that was the same one that went on mine. I thought it might be my brakes but that was a red herring. I can't imagine why a fuse would blow when starting hot though.
I hope your is just as easy. Good luck.

I know this is a very old thread, but I'm just having the same problem and a quick Google found this thread which although it doesn't quite offer the solution at least got me going again!

So, I'm just back from the Hard Alpi Tour on my X Challenge - what a ride!

Had some issues with the XCh blowing Fuse F... pretty much every couple of hours at one point!

It started 90 minutes into the trip as I pulled on to the Ferry at Dover and the bike just cut out, engine, lights, display, everything. I thought my trip had come to a sudden end before it had even begun, but a quick Google over breakfast (which found this thread) and special access to the car deck allowed me to swap the fuse and had me going again and I was able to ride off in to France.

As the bike got hot, riding down the Paeage to get the miles done, it would blow the same Fuse F while standing at toll booths, fuel stops etc with the engine running waiting for the others. Then as we went on I'd turn off to let the engine cool for a minute or two at these stops but the bike would blow the fuse as it went through its diagnostics when I turned it back on.

Then, on one occasion it blew as I was riding down the motorway! Wasn't especially hot, hadn't turned the bars or anything. However, with a pocket full of fuses from service stations I eventually made it to the start of the Hard Alpi... where it blew just as I was about to exit Parc Fermé! Not a great start!

Over the course of the rally which took me just over 23 hours I blew a load more fuses – I set off with a bag of 10+ and had just 2 left when I finished. It was a mixture of blowing when hot while standing, blowing when I turned back on after a few minutes off (although it would usually be ok if I left it off for more than half an hour or so), blowing once when I kicked the sidestand up (although that may have been coincidental) and one time it blew in the depths of the night in the middle of nowhere with nobody else around as I was descending a steep trail in the pitch black - engine off, lights off, everything just cut out! Scary!

However, after the Rally and for the next 3 days trail riding and 2 full days back home over some great Alpine passes and a load of dull Paeage it didn't blow a single fuse!

I'm going to have to strip the big Touratech tank and everything off to give it a proper clean as it's caked in Alpine mud and crud, but does anyone have any ideas where to look initially for what might be causing the issue?

Quite tricky as there wasn't much pattern to when it would blow. My thoughts were that the big TT tank was restricting airflow to maybe the starter relay (which operates off that fuse), the reg/rec or maybe even the ECU under the seat. Then again it may be as simple as a cracked/bared wire that I'd shaken into a position where it was shorting whilst laning before I went away and shook back out of the way whilst doing the HAT!

Any advice on where to start would be good!