...Sparkplug. I'm really hoping this is the last motorcycle question I'm going to be posting here. Long story short I have a really bad problem with overheating. To the point where the coolant is boiling over into the reservoir tank, and out onto the ground.

I've tested the entire cooling system for blockages/leaks. I've tested and replaced the thermostat. I've replaced the fan temp switch; the fan works great now. There are no air bubbles of any problematic apparency in the system, I'm using the correct coolant, the water pump is functioning exactly as it should, the radiator cap doesn't seem to be leaking, and it hisses when I depressurize the system when its hot.

In short, I believe the entire cooling system is functioning as it should.

But I'm still overheating and boiling coolant.

Blown head gasket is a no-no. No white smoke from the tail pipe, and the oil wasn't milky.

Onto the spark plugs! I've heard that running too lean can cause the engine to overheat. So naturally I yanked the spark plugs out of my bike. After I'd discarded the unimportant parts (i.e. the rest of the motorcycle) I examined the spark plugs. But I can't 'read' them definitively to assess weather I'm running lean or not. Here are some photos:


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These are still new spark plugs. Only about 100-150 miles on them total. Although I did get the bike up to some pretty high revs riding it. I'm just curious if that little layer of white at the tip is indicative of lean running.

Also it seems 'reading' spark plugs is kind of a redneck way of telling if its running lean. But if it is running lean, wouldn't it be as simple a fix as turning the air screws a little tighter?

Any ideas that you guys could throw my way I'd really appreciate! I suppose the air filter could be the next thing to check. I'm running under the assumption that the jet sizes are stock. Maybe I should check that too...