I've done due diligence and searched the forum, including Mothman's epic post about replacing his thermostat and fan (that guys posts were epic), but as a mechanical noob I thought I'd ask for a quick check to see if I'm in the right direction;
The bike has been running the fan a lot since before this years NVM, to the point that I took it to my local mechanic for a once over and to buy a litre of coolant to top up the expansion tank. We checked the rad and it was full, so technically it was not low but somewhere along the line it lost about 300ml of coolant (the amount I topped it up with).
Since then the bike has done some hard miles; NVM, Scotland, Isle of Man, London a few times and a camping weekend in Cornwall. Mostly fully loaded and near full throttle.
On the way back from IoM I got drenched and the bike started farting and burping. Stick coils and spark plugs replaced and while I was at it also removed my non-functioning Scottoiler and did the vac port mod on the throttle bodies.
Since then the bike ran well. A bit more backfiring on throttle off than before and occasionally the FI light comes on if I'm cruising on very low throttle at 65-70mph which it has always done since I had the SP Engineering stubby fitted (too much exhaust flow leaning the mixture more than the FI can handle perhaps?).
This weekend riding up the M5 approaching Weston, doing some naughty filtering in warm weather the temp warning light came on at above motorway speeds. Pulled off at the next junction, rode her a mile to the garage at low speed to try and get some heat out of the coolant.
What I Saw
No coolant loss, no dribbles under the fairings, no gurgling from the expansion tank. Weird! I thought the temp warning came on at 115ºc?
Took off the side fairing, couldn't see any dampness around hose clamps or the rad cap..nothing obvious.
Took off some more fairings; spotted a frayed wire at the 5'o clock position on the clutch cover (figured this might be a cam sensor? - wrong!). Dunno, but frayed cables are never good so cleaned it with WD40, wipe with alcohol wipe and rewrapped in electrical tape. Perhaps a grounded signal was upsetting the timing? Nah, it was running fine, good enough to overtake everything on the M5 anyway.
Oil looked OK, bit dark for 3k mile old but given how much work its done nothing out of the ordinary. No creaminess, no particles, foamy gunk. So hopefully not a head gasket gone.
Here's what I'm thinking.
1. Thermostat failed
2. Temperature sensor failing, sending wrong signal, ie. saying hot when its not
3. Temporary/intermittent pressure loss - rad cap, hose clamp, somewhere really awkward
4. Lean mixture/injection/timing issue
5. Failing water pump/mechanical seal
Am I looking in the right direction? Anything obvious I've missed