this is not the right forum(tractor wrong color) but i cant get an answer on the other one. working on a tractor for friend. had it running three times with no knocks at all, but carb needed rebuilding. rebuilt carb, started tractor, and it is knocking. almost like a rod noise. drained oil,(almost pure gas) pulled pan, and everything looks fine. can get no slack out of rods, pistons, rod bearings or anything. pulled valve cover, and everything seems fine. but still has knock. all i done was rebuild carb. tractor ran fine with no noise the day before, now a knock. is it possible that the gasoline just washed all coating off internals, thus the knock? cant see a rod just turn loose all at once!
- Thread starter bdunegan
- Start date
teddy52food
Well-known Member
I hate to say this, but I think you had a loose screw in the carb that got on top of the piston when you started it up. Take the plugs out and use a good flashlight to see if you can find it. You may find it stuck in the piston. Get it loose and get it out with a magnet.
glennster
Well-known Member
with the diluted oil, its a good guess you lost a bearing somewhere, or a wrist pin. put a can of stp oil treatment in it to thicken the oil and see how it sounds. if it still knocks, while the engine is idling, one at a time, pull each spark plug wire or just short the plug with a screwdriver to see of the knock stops. if it stops knocking at cylinder, thats the one to look at first. try plastigauging the rod bearing and see how far out it is. then you may want to pull the piston and check the wrist pin. while the oil pan is off, plastigauge the rest of the rod and main bearings.
While you have the pan off take a look at the rod bearings to see if they worn or the rod journal is scored. Do one at a time and make sure you reinstall the caps in the right direction and if they look ok retorque the rod bolts too. Pull the main caps too if you can get them off. Hal
it has never ran over ten minutes at a time with the old diluted oil in it! really not even enough to move the temp guage, and nothing over fast idle then. would this still be enough? just visual check, and reached in and get no slack out of anything anywhere. put trans in high and rocked back and forth, and can see no slack. as for the carb, unless something came loose, everything was tight when put back together. can pull the wires one at a time while running, and knock is still there.
Allan in NE
Well-known Member
Piece of carbon on top of a piston?
I'd soak 'er overnight with GM's top engine cleaner and give 'er another try.
Allan
I'd soak 'er overnight with GM's top engine cleaner and give 'er another try.
Allan
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