URGENT HELP NEEDED JD MODEL A ENGINE KNOCK
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Posted by Dave Kolbenschlag on April 27, 1998 at 13:27:19:
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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