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Paul D., If valve lash looked OK before you pulled the head, my first suspect would be cam timing. I'd guess that someone had the timing cover off at one point, removed one or more of the gears and put it back together 1 tooth off. As you've already got the head off, stick a dial indicator down on the exhaust lifter for #1 while you watch #1 piston reach TDC as you turn it. If the lifter is still moving as piston TDC exhaust is reached and passed, that's probably retarded cam timing which would explain an exhaust valve being open while the piston was starting an intake stroke, i.e. sucking. I think the sprockets on your tractor work out to about 1 tooth = 6 or 7 crank degrees. A few degees of retarded cam timing is usually good for low end torque, therefore good for a tractor - but on this one somebody may have gone overboard with that idea - or just made a mistake on re-assembly. Hope you have a manual to show you where the front sprocket timing marks line up. I think some new gen JD's just have one or two marks and you've got to kind of protractor your way into setting the other gears. You might want to get a big degree wheel to help double check your work, as getting the cam timing advanced a few teeth can make valves kiss pistons - which is guaranteed to ruin your Chistmas. Good luck with it. Steve
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