Kubota L275 low rpm knock

[sos1]

Just bought tractor with new rebuild of engine. It didn't
seem to make this noise when test driven. Now it has a
low rpm knock that seems to disappear at higher rpm.
Tractor has good power and runs well. Is this a quirk of
the L275 or have I got a bigger problem?

 

[Eagleview]

What is the oil pressure at idle ?

Did you get any warranty when you bought it ?

It could be serious , a big end bolt may have been left loose , a bearing could have spun . Really it could be anything . You must first get in touch with the seller and see if you can find out some more info on the rebuild . With a bit of luck it may just be a Diesel knock .

Try putting a piece of dowel , stiff hose etc. to your ear and move the other end against and around the block while it is idling , you should be able to pinpoint the noise . Please come back with anything you learn .

 

[David-Davies]

do you have a loss of oil pressure. If so you could have turned a rod bearing. rod's only knock at idle, mains knock under load. Did you run the engine for a couple of hours between 1200 - 1800 RPM, no load, to break the engine in. Do not let a new engine idle for more than five minets, after a couple of hours of break in. The person that you bought the tractor from should have run the engine, with no load before you got it. Diesels can knock quite bad at idle, especially if the timing is too soon. Pay close attention to your oil pressure, for any changes. Contact the person who rebuilt the engine, with your concerns.

 

[sos1]

Oil pressure is good. Are you talking about engine timing or fuel timing?

 

[David-Davies]

Fuel timing, If the gear set is'nt set right the engine probably wouldn't run. Did the person that rebuilt the engine put in new sleves, and pistions and rist pin bushings. Or was the block bored out and new pistions, and ristpins bushings. I just had my engine rebuilt, the machine shop, didn't replace the rist pin bushings, or the camshaft bearings, and didn't resize the con rod that spun. I had to redo the engine, at a different shop. You should have some one that is qualified, look at your engine.