I have a 1990 Kawasaki 4X4 Bayou 300 cc. The engine runs fine except when engine is under no load (just driving or letting off the gas when slowing down).

Then it has a knock in it. It did not do this until now. I had it at two different dealers, and they have no idea what it is, and they are not that interested in tearing it down to find out. There is not a lot of use in this machine and should be in great shape. Is this going to blow up? Any idea what this could be?
Thanks
Land King

 

Hard to tell w/o hearing it. I find it hard to believe a reputable dealer would not know. I test frove machines at the dealer that did exactly that.

A loose piston would probably be louder when cold and not so bad when hot, that is not what you said. I dunno, maybe it could sound like that.

I don't think the valve train could do that, does not matter about the load.

A worn rod bearing might do it, loose wrist pin bushing in rod probably would not do that.

Air cooled engines with loose head bolts make a funny dull popping sound that's louder the harder you press the gas. Does that sound familiar? You could see soot between the head and cyl.

A loose/stripped spark plug usually makes hissing sound.

Are you sure the timing isn't advanced and you are not ust getting an ignition knock? Try higher octane.