Neil - correct, the shaft is snug but rotates freely. Phil - I've attached a video I took earlier in the year when I first noticed the problem. You can see the slight gap after the decompression shaft is rotated into the start mode. When I reinstall the rocker arms I'll double check everything after I set the valve lash.

I'm thinking valve stems are to short or wrong valve seat depth. Has the head been reconditioned?

Hi Team,
the boys are onto it with the valve stem length being short.
If in the past the valve heads were recessed into the cyl. head seats by wear, what can occur is that you get the opposite effect--the valves will not close due to button resting on the de-comp. bar slot and holding the valve open. IF someone ground the top of the valve stems down to gain de-compression clearance then when the head is re-conditioned by fitting valve seat inserts then the valve stems are now too short.

One kosher fix would be if you can get suitable valve stem caps from the trade for that size stem and thick enough to work.
A dirty fix would be if you can remove the buttons, if they are not spot welded into the rocker arm, and pack the buttons out enough to get the approximate 0.125" decompression clearance at the de-compression bar slot. or weld up the buttons and dress them off to match the contour they presently have.

https://vwparts.aircooled.net/v/vspfiles/photos/LASH-CAPS-8MM-2.jpg?v-cache=1397903792

Cheers,
Eddie B.

Thanks everyone for your input on this. I've had the tractor for nearly 3 years, and haven't done anything to the diesel engine except new injector nozzles. Neil - I thought the decompression was working before I pulled the pony, but apparently it must not have. Eddie - the buttons don't appear to be welded onto the rocker arm. Thanks for the advice. I'll take a look at the valve stems and look into modifying the buttons.

Also make sure the lever is indexed on the shaft correctly
Chuck C

It's keyed and is centered in the lever. Doesn't matter what position it was in, just to much clearance between the rocker button and the shaft. The button on the rocker arm is not in the correct position when the valve is closed and will not contact the compression release shaft when set on compression, as in the video shown.

that is why its a good idea when reconditioning a head or doing valve seats to replace the valves or atleast check they are within spec as it costs the same money in labour to do it all again. some may think its going over board but when its right its right and its good to know its right. plus it saves money in the long run.

i replaced a head on a nissan once it was cheaper to buy a complete head minus camshaft than recondition the original.

 
I was hoping to be able to remove the button and put a couple of washers to raise the height of the button and reinstall back on to the arm. Not a good angle to get a solid hit with a punch and hammer. Tried but didn’t move. Looks like some sort of tool is needed to press them out. Thought about using a dremel tool to cut along side of the arm thinking maybe that might loosen the button and squeeze it back together with the vice or drill press. Thoughts?

Looks like the tappet adjusting screw is turned in awfully far, is that the way it was when removed from the rocker shaft?