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

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

Comments:
: : : Thanks to all those who have offered help. : I finally did tear the engine down : and everything top side was fine as I had suspected. I "think" : I have located the problem, won't be : certain untill its back together. Waiting on new : gaskets right now. What I found was in the crankcase : the camshaft drive gear is fastened to the collar : on the camshaft with three allen head cap screws. : My JD parts breakdown, for some starnge reason, : does not show what type screws are supposed to be : in here. Someone had put the allen head screws : in, long enough to come through the gear : (the gear is threaded, the collar on the shaft : is not) and then put nuts on the ends. : These nuts face the left bearing housing next : to the flywheel side of the crankcase. : Two of these nuts had worked loose and were scarred : and polished where they were apparently banging : the bearing housing. I removed the nuts and : put lock washers under the heads of the cap screws : thus shortening them to where the do not protrude out : of the gear. There is now good clearence there. As : my noise was in the reciprocating parts and : all bearings, pins, pistons, valves check fine : I think I can safely assume this was the : problem (fingers crossed!). : Dave : : : : : 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

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