Anyone know what this knocking might be?

[Undorh2o]

Drove home from work in the morning just fine and went to start her up 12 hrs later to hear this sound. Gets worse hitting gas.
https://vimeo.com/186040711


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[Peanut Butter]

Sounds like a dropped valve. Take a solid piece of wood, like a dowel rod (broom handle), and put it to exhaust exit and to your ear. It will help you pin point what cylinder it is. Now you can do a pressure test for lower end, etc.

 

[gert]

its shaking around like its running on 3 cylinders and your knock sounds like its at half speed of the motor which would indicate a valvetrain problem. Like Peanut said, a compression test will tell you pretty quick which cylinder to look at

 

[Peanut Butter]

Like Peanut said, a compression test will tell you pretty quick which cylinder to look at

Dowel Rod - old school, sorry.

 

[gert]

Dowel Rod - old school, sorry.

I have heard of it before just not with a dowel, I have seen it with the stethoscopes


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[hagar]

I've heard carbon knock sound that bad.
Not as common as it used to be with better gas/oil additives...but your description of how it started makes it a possibility. Piece of crud falls off valves rests on top of piston/valve seat.
You have nothing to lose,...rev it up and empty a can of combustion cleaner down the throat....let it sit a while....then fire it back up.

Unless you have already figured it out.