Re: URGENT HELP NEEDED JD MODEL A ENGINE KNOCK

Subject: Re: Re: URGENT HELP NEEDED JD MODEL A ENGINE KNOCK

Comments:
: : I have a 1948 JD model A which has suddenly : : developed a loud and hard engine knock. : : This developed over perhaps an hour of light work. : : I first noticed it when I throttled to idle for a : : moment. I then decided I better head home which : : took perhaps 30 min at mid throttle. When I arrived : : the engine was clanking loudly, oil pressure stable : : and correct, temperature okay. : : I opened up the crankcase and have checked the rods, : : journals, main bearings all were in spec. I removed : : the clutch/pully to isolate from that and the : : transmission. I removed and re-installed the : : flywheel making certain end-play was correct and : : the flywheel is tight on the crank. I pulled : : the camshaft bearing caps and the bearings look ok. : : The camshaft does not feel loose in any way nor : : does the crank, rods or pistons. Clearences are : : in specs. Pistons and pins look ok from the : : crankcase side. Head is not off but compression is : : good, engine starts and runs fine except for the : : knock. Ign timeing is correct. : : At idle the engine sounds like someone is beating : : on the crankcase with a large hammer! At mid : : throttle the speed of the knock increases, it : : follows engine rpm. At above idle speeds the : : whole tractor vibrates as if being pounded : : or something far out of balance in the reciprocating : : parts. It seems like imminent self destruction : : yet I can find no bad, worn or loose major parts. : : I am wondering if anyone has any ideas before I : : go to a complete tear down and then find : : it was something like a flywheel problem or something? : : flywheel splines and crank splines are in good : : shape. This knock developed : : about 5 hours of operation after having : : the flywheel off for replacement of a : : main bearing seal. The first 5 or 6 hours after : : replacement of the oil seal were smooth : : and normal. : : Any ideas appreciated!! I kind of NEED the tractor! : : Dave : I remember reading about a similar problem in some posts a couple of months back. You might try searching in the archived posts, maybe even on the John Deere board. I'm no expert on these tractors but I would check the flywheel installation since the problem happned so close to having the flywheel off (5 or 6 hours). I seem to remember that there is a right way and a wrong way to reinstall the flywheel and it's hard to tell the difference. Good luck.

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