OK so I did a little tune up on my 95 GSR with high miles. I changed the plugs, cap, rotor and air cleaner, yadda yadda. I had a little trouble with the plug by the timing belt since this new Bosch plug had a nicked thread and it became really tough to turn on the way in. I spent some time threading in and out an old plug, backing it out and cleaning the threads each time. A new plug then was properly installed.

So the car fires right up and within about 3 seconds its HAMMERING! WTF? I'm not saying that the bearings were perfect but it was running good and wasn't hot or anything certainly not hammering. Its kind of a light hammering but more than a valve tick or tap.

If you are losing a connecting rod bearing could it fail this suddenly? Is it possible some crap fell into the plug hole or something fell into the intake when I changed the air cleaner?

I like this car and might drop the oil pan to see what is up with the con rod bearings. If one is running out I could buy some time by replacing the bearings.