|
Britt Misker
08-27-2003 16:16:19
|
|
Re: John Deere 70 .. broken valve spring ... chang in reply to andy, 08-26-2003 18:17:07
|
|
|
There is a safe way to change valve springs out in the field or where you don't have an air compressor. I use this method on aircraft engines all the time. First remove the rocker arms to gain access to the valve and spring retainer. Then remove the spark plugs. Find a 20 to 30 foot length of 3/8" rope that will fit through the spark plug hole. (A John Deere may take up to 50 feet of rope.) Then, with the piston at bottom center, feed the rope into the cylinder. (Leave a short amount of rope hanging out of the spark plug hole so you can remove it later.) Then turn the engine BY HAND until the rope is held up against the valves. At this time you can compress the valve spring and remove the keepers. I have a tool that hooks under the rocker arm shaft and presses on the spring retainer. (With the rockers removed from the shaft.) Once you have removed the spring, it is possible to actually push the valve part way into the cylinder (after removing the rope) and by looking through the spark plug hole, inspect the valve face for wear or damage.
On certain aircraft engines that have experienced sticking valves, I have removed the manifold and secured the valve with safety wire. Then I push it into the cylinder and ream the carbon from the valve guide. Following that I have been able on some engines to bring the valve stem out through a spark plug hole and clean the carbon from the stem with Scotch Brite. Following that, working through the manifold opening in the head and through the spark plug hole, I manuver the valve around and reinstall it in the guide. Then redo the rope trick, install the spring and keepers, manifolds, rockers, etc. and voila, start her up. Just rember, turn the crank BY HAND to compress the rope against the valves and when done turn the engine in the opposite direction to relieve the pressure from the rope. Don't put the rope in the cylinder until the rocker arms are removed, or you could get rope caught under the valve. This proceedure takes some patience and dexterity, but it is definately quicker and cheaper than taking the head off.
Good Luck
Britt
|
|
|
