50HP Honda knocking problem

[MattInFL]

I've got a 1999 50HP Honda that has suddenly developed a metal to metal knock sound. The sound is coming from the block, seemingly where the #1 or #2 rod bearing would be. It's louder when the engine is hot, volume and frequency increase with RPM and you can hear it in neutral or in gear. The Honda mechanic took a very quick look and dismissed it as normal for an engine with some hours, but he wouldn't listen to me when I told him it started "suddenly" and gets louder when the engine is hot. Compression on all cylinders is in spec and within 2psi of each other, the engine burns absolutely no oil, the valve train is all quiet and an oil analysis comes back as normal. Has anyone with Honda experience seen this before and can you offer me any tips? I suspect a rod bearing, but the oil analysis was normal which left me confused. Is there anything else in that area of the block that could make noise? I'm afraid to use the engine as it is now.

 

[Skinnywater]

Re: 50HP Honda knocking problem

I recommend you get a second opinion.<br /><br />If it is as you suspect, a rod knock, you can verify this simply enough.<br />Remove all the spark plugs. Remove the plastic cover over the flywheel. Rotate the engine by hand to bring each piston individually close to TDC.<br />While each piston is close to TDC, rotate the flywheel by hand clockwise and counterclockwise back and forth a few degrees. While doing this you may be able to actually hear or feel the play or clearance between the rod bearing and crank. With careful observation of the piston you will be able to visually observe this play through the spark plug hole.<br /><br />It's possible that a broken or loose connecting rod cap bolt would'nt give you an adverse oil contamination report.<br /><br />It would be nice to have a legally prepared repair order by the mechanic stateing that this was normal. So when on your next trip at 5500 RPM the rod blows through the crankcase. He will be legally obligated to pay for the crankcase.<br /><br />However this goes, please keep us informed.