[RedDevil]

Spark plugs. Spark plugs? Spark plugs.

When I bought my old new to me Nissan Almera I first had a test drive and it did well.
When I took it home it was awful. It lurched and held back and was impossible to hold steady.
So I took it back to the dealership and let them investigate.
Turns out they had cleaned the engine block with a high pressure hose, then removed all the electric leads, dried them and put them back where they belonged.
One or two of the spark plugs remained wet and shorted...

I had loose spark plugs on at least two of my bikes. Improper gap width. Lead bridge, charred over, oiled over.
If I suspect a misfiring issue now I pull the spark plugs one by one and check if they look clean and do spark when properly grounded.
Judging the state of the engine by reading the spark plugs solved about half the issues I've had over time.