Kohler Knocking

[Anonymous Poster]

HUGE lesson learned here - always check the parts you received. I was sent the wrong piston and ring set. I never checked them out when I got them, I just took it for granted and installed them. So I've been running the engine on an undersized piston assy!! That explains the large ring end gap. I'm getting them exchanged, no physical damage was done to the block, and the supplier was very apologetic and helpful to get me the correct ones, including the new rod for no additional charge. These things happen, and I could have averted it from the beginning by double-checking. This has definitely been a learning experience for a first-time rebuild!

Thanks to all those who helped out with advice!!

Jeff

 

[normde2001]

Sure had me scratchin' my head. Should go smoothly now.

 

[bgott]

I was going to to throw "undersized piston" in there, too, but I couldn't see how it would run ten hours before knocking!

 

[Anonymous Poster]

Ok. I need help before I pull out what's left of my hair! I got this thing put all back together, everything torqued correctly, rod on the correct way, everything was checked and double checked while doing it. Everything was lubed up really well, poured about a teaspoon of oil on top of the piston, made sure it was lubed up well, go to start it up ... cranked a few times, started up, ran about 10 seconds, and started knocking!!! What in the world am I doing wrong??? The bore was checked with bore mics, got the correct parts, I'm at a loss!! New key on the crank, the flywheel is not loose ...

Anybody got any ideas??

 

[Anonymous Poster]

are you 100% sure its the engine? I've heard outboards knocking,put stethascopes on them,swear it's in the power head,and be in the lower unit.Did you ever check the valve guides?If it's a bad knock in the piston/rod assembly you don't have to tear apart to check.Pull spark plug,put screwdriver in plug hole,turn to tdc,turn back 1/4",hold flywheel,push down on piston w/screwdriver,any movement; trash.I don't think this is your problem.Could a valve be binding up? Is this an overhead valve engine?If it is is piston slapping valve?Referring to post on head gasket thickness.Could be a weak valve spring causing valve to float.

 

[Anonymous Poster]

The spark plug is offset between the piston and valves on this engine, not over top of the piston, so I can't do the screwdriver trick. It sure does sound like it's inside the engine, though. A hard, sharp knock. Sounds like someone whacking it with a hammer, actually. I think I'll do the stethoscope trick while someone cranks it over. Head gasket is the same thickness. Before I put the head on, I made sure the piston wasn't coming up past the top of the bore. It's not an overhead valve engine, and the valves seem to move fairly good. They were replaced in the rebuild also.

Thanks for the help! It sure was a disappointment when I fired it up last night!

 

[normde2001]

I honestly believe you are asking the wrong guys /forums/images/graemlins/confused.gif. These guys are the "pro's" and have probably seen your problem before and have better suggestions.

 

[normde2001]

I read your post over there, Jeff. That oughta' work if anything will. Those guys are good.

 

[Anonymous Poster]

Thanks, Norm. We'll see what happens! I can hear it a bit by rocking the flywheel back and forth when the piston is at TDC, could this be a valve? I just can't believe that a valve could make such a loud knock.

 

[Molerj]

I've been reading your post both places. Being that you can hear the knock by rocking the fly wheel you should be able to narrow down to where it is coming from. Maybe by removing the head & rocking it back & forth you can see what is happening with the valves & piston.