Hi Guys, My 2007 XT660X (37000kms), standard pipes, not modified. The engine suddenly sounds very muffled at cold startup after standing for a day or so. The bike also doesn't seem to rev through and engine dies and this morning didn't even start again after dying. It stood for a few minutes and started again. It feels almost like a 2 stroke when cold.. Like you have to rev it through, but for 5 - 10 minutes before bike has any power. It sounds like there is a build up of pressure or blocked passage inside from what it sounds like. I also noticed today at the same time there's coolant dripping from the weep hole at the bottom of the water pump. I get the impression that this muffled noise and water dripping is related... almost as if there's too much pressure somewhere inside. Excuse the explanation, but this is what is sounds like from a NOOB point of view. It's something I'm only experiencing recently. I'm worried about reliability at this stage and if I should look at Head gasket and not only water pump seal if the problem is coming from somewhere else. Coolant reservoir level not dropping visibly. Once the engine warms up the engine sound changes to a more open/ less choked sound and exhaust sound also sounds more open / clear...

Now non starting, engine swings. Error code 30 & 43 shows up. Lean angle sensor & Batt Voltage control error. Battery was charged overnight, but on Diagnostic D09: Shows battery voltage 0.0....? (with cut off switch in off position. When cut off switch in on position it shows 12.2, but sounds like fuel pump running until I switch cut off switch off, while on D09 in Diagnostic mode. D08: 0.6 (within range...) Engine swings fine, lights go on, etc..?

Spark plug is black & sooted, inner most part wet (fuel). Upon changing plug bike started, but doesn't rev through the range and jerks numerous times during the rev range in each gear. Only drove it for 1 km. Snorkel is removed, had decatted standard pipes on, now completely standard pipes. But seems like bike is running rich. Also quite heavy on fuel compared to other XT posts I read. I get the feeling I need to get more air, but many say it already runs lean from the factory and apart from snorkel removed it's pretty much a standard bike. The plug being fouled and being so black (7e plug) made me wonder if I should go one plug hotter, but with bike being standard I thought it's not justified and must rather find a way to make it run leaner.


Help/advice would be much appreciated.
Thank you