CV16S new vibration at high speed, low load

Scotts 1642 tractor. Probably underpowered for my hilly yard.

Recently the sound of my engine changed, and I've noticed increased vibration. But, its a little strange. At idle/lower speed, engine seems normal. At high speed with mower engaged, seems fairly normal. At high speed with lower load (no blades engaged, driving back to shed or towing a garden trailer), that is when it sounds wrong and vibration is higher than normal. At high speed parked, cowl open, I can see more "shake" in the engine than I remember.

The last time I used it before noticing this problem I was mowing high grass/weeds, and a few too many times it started stalling from the load.

I'm puzzled at what might be wrong. If I messed up the connecting rod or crankshaft, wouldn't the vibration be bad regardless of load?

I would appreciate any guidance. I've never opened up a Kohler engine before, but have worked on some tecumseh engines way back.

I struggle with whether to stop using it before problem gets worse, or just keep going. Engine does blow some smoke at startup when hasn't been used for over a week.

I've started contemplating replacing it with a Briggs Intek 19hp, but the exhaust would need rework since that is a side port instead of bottom port. I don't have skills or tools for making my own pipes.

First, tighten all the bolts that hold the engine to the mower. While you are under there look at the belts and pullies. That is where I would start.

Well, I should have listened. Check the engine bolts.

I put this off, the vibration was less pronounced at times. I was starting to think it was belt/transmission, as I had lots of problems with that a year back.

Today when I went to start it, engine was shaking wildly, literally moving. Which is odd as when I put it away last, I thought the problem was not as bad.

So, I check the bolts. 1 tight. 3 missing! one of the three couldn't be replaced, looks like it sheared.

I replaced the two missing bolts, huge improvement. Almost back to normal again. Now I get to figure out how to remove the sheared bolt, i suspect that will be miserable.

If you can post some pictures of the sheared bolt.
Is it broken inside the hole?is there some sticking up?

Scrubcadet10 said:

If you can post some pictures of the sheared bolt.
Is it broken inside the hole?is there some sticking up?

Click to expand...

its broken inside, feels like about about half way in from the poker I was using. I also suspect the exposed threads are damaged, as I can't get the new bolt to start threading at all (loose). Until I pull the mower deck and belt guards, I can't get a good view of it. This of course was the least accessible bolt on the frame.