setting valves

[River Riley]

hi my name is River and im 12 years old and im trying to set the valves on my grandpas old 620 John Deere and i have never tried this befor I think I understand the book right make sure all valves are closed then set a gap at .20 is that right? any advise? both dad and grandpa are passed so im on my own trying to save family tractor thanks River Riley
 

[rustred]

yep, so they are closed on the compression stroke on tdc. have plugs out and turn engine over slow and can feel the compression blowing out with your thumb over hole. continue to turn over till you reach tdc either by timing marks or using a pop straw to feel the piston. then set that cyl valves and do the same for the other one.
 

[Kent Petersen]

.020 is a hot setting. set to .022 then you wont have to go back and reset
 

[River Riley]

Thanks for all the help! what timing mark do I line up for top dead center is it lefthand exhaust? thanks agin
 

[Lee B]

Nope, not that mark. Left exhaust mark will line up when the exhaust valve of the left cylinder is just starting to open - so you DON'T want to set the clearance for it then. You want 'impulse' lined up for setting the left side, there is no mark for the right side but it is exactly 180 degrees further from impulse (upside down impulse). Those marks come around twice for every adjusting opportunity so you'll have to pick the right one.

For instance, line up left exhaust mark and verify that the left exhaust valve is starting to lift on that particular go around or go around again where it will lift. Back up (ClockWise) the flywheel until impulse is upside down and parallel with the floor as far forward as possible. Set right side valves and rotate impulse mark in correct direction (CCW) past proper line up once and stop on second time there to set left side.

.022 cold and if it's too noisy you can cut it back .005 or .008 without too much danger. There is actually much more slack in the valve train that occurs some 30 degrees before lift off, but old timers seem to have troubles understanding and finding this slack spot and then there is NO mention of it in ANY service manual either - but it's still there. It contributes a great deal to valve train clatter on mine if I set it to .020 hot - so I don't. I run a little closer and quiet. As keepers of the flame, you youngsters should know about that extra slack spot and verify that it's there.
 

[River Riley]

Thank you for all your help River
 

[Lee B]

You are most welcome River. One more thing you might find interesting is to use one 'flat' of an adjusting nut for an 'in the field' adjustment equivalent to using a .020 feeler gauge. In other words, close up the clearance to zero using the adjusting nut and then back it out exactly one sixth of a turn which is also one flat of the adjusting nut approximately. Tighten down the adjustment nut and finish the field as it will work until you can get a proper feeler gauge on it.