[bookm]

At 5500 miles, I'm rebuilding the top end due to a burnt piston.

I have the full kit, ready to wrench, but I'd REALLY like to find out what the cause was.

I see no issues with the intake boot which would cause a lean condition. So I'm leaning towards an overheat issue.

I've noticed my temp gauge reads very cold... barely rises unless I'm putting along real slow through a tight, twisty trail, then it rises to normal.

So I'm wondering if maybe I'm getting no coolant circulation. Perhaps the engine is way-hot, but no hot water is getting up to the sensor.
I have the cylinders off and thought that by pulling the engine over slow several times, I should see the level of the coolant in the water jackets lower some. But it's not moving. It's staying flush with the block.

I have no real experience here, just using common sense.
Any thoughts on how to tell if coolant is circulating?

Thanks in advance.