LT150 knock on start and when throttling up

[boutym]

Yesterday I was out in the yard and heard a loud clammering like a wood chipper tossed a blade. Didn't think much more about it until my neighbor a couple houses up the road and asked if I could come look at his LT150. Got there and he started it and it had a loud repetitive knocking like a rod knock except that after start up it went away. However pushing the throttle up the knock came back until the engine stabilized. Oil looked good and no outward signs of a problem. Still has power and starts easily. The knock is a loud metallic knock like hitting the motor with a ball peen hammer.

 

[Richard001]

Yep, sounds like it's a rod on it's way to heaven.

Any chance that he had the air filter off and dropped something into the carb?

Richard

 

[tomplum]

It wouldn't surprise me if the engine is loose. It happens a lot on these. Mounting bolts thread in the sump from the bottom. Eventually all bolts drop but one, then the muffler cracks and the engine damages the wiring harness at the rear of the engine.

 

[boutym]

Yep, sounds like it's a rod on it's way to heaven.

Any chance that he had the air filter off and dropped something into the carb?

Richard

I told him to pull the air cleaner and check the throttle plate screws but not sure if he has yet. I would think that it should knock all the time if something got sucked in or if it was a rod going south. It's smooth as silk except for starting and throttle up. My first thought was a loose mount but didn't see any obvious unexpected movement of the motor.

 

[Dave M7040]

I told him to pull the air cleaner and check the throttle plate screws but not sure if he has yet. I would think that it should knock all the time if something got sucked in or if it was a rod going south. It's smooth as silk except for starting and throttle up. My first thought was a loose mount but didn't see any obvious unexpected movement of the motor.

Kohler's web site in their trouble shooting section talks about hydraulic lifters causing knocking sound
I would also be checking the pulley's on the engine output shaft to make certain nothing is loose there.

Dave M7040

 

[RandyT]

+1 on checking the motor mount bolts. It only takes about 1/8 turn to allow the engine to clunk on start up, acceleration and shutdown.

 

[s219]

My LT 150 would make that noise from time to time and it sounded like it was coming from the valve cover. One time I took it off and checked the lifters and saw no obvious problems. Years later I found I could recreate the problem by mowing a certain hill sideways, so I assumed it had something to do with oil not getting to the right place. Really think it was something in the valves, lifters, or related parts.

 

[boutym]

I'm going to run over there when I get a minute and check the mounts. The knock is pretty loud. I could easily see it being a mount and considering how these things are constructed the frame could be acting like a big speaker diaphragm making it sound louder than it is. If it was internal to the motor and as loud as it is I wouldn't expect it to run as smoothly as it does. Like I was saying, once the engine speed stabilizes it's as smooth as silk with no unusual noises. Now that I think about it I have a JD 212 that was making some odd knocking noises which turned out to be mounts. Completely different style motor but same principle.

 

[Dave M7040]

I'm going to run over there when I get a minute and check the mounts. The knock is pretty loud. I could easily see it being a mount and considering how these things are constructed the frame could be acting like a big speaker diaphragm making it sound louder than it is. If it was internal to the motor and as loud as it is I wouldn't expect it to run as smoothly as it does. Like I was saying, once the engine speed stabilizes it's as smooth as silk with no unusual noises. Now that I think about it I have a JD 212 that was making some odd knocking noises which turned out to be mounts. Completely different style motor but same principle.

I have seen where the mount area on the motor has cracked so the bolts appear tight but the motor can move. check carefully by cleaning with brake clean or similar

Dave M7040