Kohler Knocking

[Anonymous Poster]

I'll give it a shot. It's definitely inside, hard to pinpoint where with the shrouding on and all. But sounds like somewhere in the cam area.

And now, since I had the coil wire off and was doing some cranking to listen, I seem to have lost spark! Very weak when I ground the plug electrode against the block. What did I do now?!? But first things first - find out where the knock is!

 

[normde2001]

At TDC both valves should either be closed, (power stroke), or exhaust open on exhaust stroke. I had to look back thru the posts to see that this is a flat head so it can't be the piston hitting a valve. I would wait another day and see if Bruce, the guru that runs the other forum will have a crack at it.

 

[Anonymous Poster]

Sounds like a plan. When you rock it back and forth so one just starts opening and the other closes, is when I hear it. I pushed my thumb against the top of the piston, felt nothing. Pushed down on the valves, and you can feel it there. Funny thing is, I held both valves open with screwdrivers, and you don't really hear it. And you don't hear it when the piston is at the bottom of its stroke. It's almost like the valves aren't long enough, and they get slammed by the cam lobe? I think I'm going to open it back up tonight and see what's going on inside. This engine does not have balance gears, it's a 2-piece cam with the compression release lobes.

Thanks for all the help!!

 

[normde2001]

"It's almost like the valves aren't long enough, and they get slammed by the cam lobe"
You may be on to something there. You said new valve seats were installed, could they be wrong seats or not seated properly in the block? Do you have any specs. on how far valves open, or valve clearances?

 

[Anonymous Poster]

The valve seats were ground at 45 degree (no seats to install), and the minimum lift for both intake and exhaust is .318". Haven't checked this yet. Took the cam cover off the side of the block, and you can see the cam and exhaust valve ... the knocking only occurs between the intake stroke and the exhaust stroke. It doesn't happen between the compression and power stroke.

 

[Anonymous Poster]

well that makes it 100% in the valvetrain.Can you see the cam lobes acually loose contact?I would double check that you have correct valves while you have it open,the guy did sell you the wrong piston.If the cam looses contact visibly you have a problem.I can't remember avr. tolerances but it's in the thousandths.

 

[bgott]

" the knocking only occurs between the intake stroke and the exhaust stroke. It doesn't happen between the compression and power stroke."

Are your valve guides secure? It sounds like your guides might be floating with the valves. 3.0 Mitsubishi engines used in Chryslers had a problem with this. They came out with a valve guide with a snap ring to cure it. Those engines would knock to beat the band when they dropped a guide. Does it have to warm up to knock? The first couple of engines I had this problem with came in with timing belts out, no start. I would hang a timing belt and start it and they would run five or so minutes and start knocking. Both customers had been driving the cars with the knock for a while.

 

[normde2001]

Maybe you have something like what's happening in this thread. If the seats were ground, the valves have to be shortened accordingly. If this was not done, or done improperly.......

 

[Anonymous Poster]

Thanks for all the help on this one! I haven't taken it fully apart yet, looks like it's time to do that. I think I remember seeing specs on how long the valves should be. I'll check that out, and also if the tappets are actually losing contact with the cam. I would think if that is happening, wouldn't I hear the contact on each revolution instead of every other? As I rotate the crank, the guides do turn so maybe they are indeed floating.

Unfortunately, it looks like today is dedicated to working on finishing "her" shower installation ... lol!

I'll post back with what I find, and many many thanks!

Jeff

 

[normde2001]

The valves only open on every "other" revolution, (ehhaust, intake), the other "other" revolution is compression, combustion, valves stay closed.

 

[Anonymous Poster]

If the valestems are to long the valves shouldn't close fully wich would show in a compression checkor visibly,can't remember if you did that(crs).this could also cause spring binding which is a horrible noise.within reason tops of stems can be shortened.if valves are too short they can be seated deeper within reason.your machinist buddy would be the best one to decide that as he can see it.that is if either of these is the problem

 

[Anonymous Poster]

Sorry, my brain was fried. Of course it won't knock between the compression and power stroke! Like you said, they're not opening! Thanks, Norm! They sure do look like they're closing all the way. Unfortunately, I'm going to have to delay it a couple days, got the "honeydo" list to finish up. I'll let you know what I find.

Thanks!
Jeff

 

[Anonymous Poster]

Well, I finally had a chance to get back to this guy, thought I'd let you know what I found out. Ended up taking the engine to a local Kohler expert to have a look-see. I figure if he's worked on them for 30+ years, he can figure it out! He took out the crank, cam, and valves. Checked all the specs. The only thing he found was the crank end-play was on the low side, between .004-.005" (same thing I found also). Spec is .003-.020". The only thing he did was put in another shim for the crank, and button it back up. It's been sounding good for 8-10 hours now. Maybe that's all it was. He wasn't too concerned with the slight knocking when rocking the flywheel back and forth, said he's also seen that and that wasn't causing the hard knock. I guess if it ever starts again, I'm going to load up the tractor and take it to him to listen to.

Thanks to all those who helped me out on this!