JD LT155 Engine Problem

[jpsdeere]

I have a 2000 LT155 and the engine has started to vibrate/shake more than usual and is also louder than usual (or so it seems.) When I burp the throttle, it sounds as if there's some hammering from the short block. Runs fine at idle but again, loud and more than usual vibration at operating speed. This is with or without the deck engaged. Is there a counterbalance mechanism that can fail or something that could cause timing-like symptoms? Hard to articulate but trying to avoid a teardown or replacement. Leakdown test was good (10%) and crankcase is spotless. Part of me says run it until it dies but not in my DNA. Thanks for any thoughts/suggestions on how to proceed.

 

[jinman]

I would pull the PTO drive belt off and then start the engine to see if the vibration/sound is still there. The pulley can easily be grabbing the belt and causing a knocking sound.

 

[SandburRanch]

Check the motor mount bolts. They've been known to loosen or break completely.

 

[jpsdeere]

Belt is already off but will check the mounts. Thanks to both for the quick responses...will let you know.

 

[jpsdeere]

My apologies for the delay in following up but wanted you to know that the problem was loose engine mounting bolts. Of the four, 1 was missing and the other 3 were hand tight. The engine has never been out and while I did "shake" the engine early in the troubleshooting, it was not loose enough to see visible movement but certainly loose enough to vibrate when running. Bootom line is that it never occurred to me that the engine bolts would loosen or drop out over time.

Thanks again for the quick input on my request.

PS. The engine has never been out as the only dealer service in the last 11 years has been a couple of winter tune ups.

 

[saltymower]

I have a 2000 LT155 and the engine has started to vibrate/shake more than usual and is also louder than usual (or so it seems.) When I burp the throttle, it sounds as if there's some hammering from the short block. Runs fine at idle but again, loud and more than usual vibration at operating speed. This is with or without the deck engaged. Is there a counterbalance mechanism that can fail or something that could cause timing-like symptoms? Hard to articulate but trying to avoid a teardown or replacement. Leakdown test was good (10%) and crankcase is spotless. Part of me says run it until it dies but not in my DNA. Thanks for any thoughts/suggestions on how to proceed.

When the engine mounting bolts get loose or fall out the engine tends to move backwards. This can cause damage to the muffler making the engine sounds louder.

 

[Gator6x4]

If the engine mounting bolts are not loose or missing, a loose connecting rod bolt or nut will also make a knocking noise and cause the engine to vibrate. Most small engine use wire to secure the bolt or nut.