Small Engines (Lawn Mowers, etc.): camshaft replacement on John Deere 445, john deere 445, plastic polymer

Question
Hello Paul:

I have a 1997 John Deere 445 that quit spontaneously one October day.  Long story short, cleaned carb, checked all fuel lines, all electrical and plugs, and all is good with them.  Then read that these years and models had plastic polymer gears on their camshafts and needed replacement to metal gear camshafts around 1000 hours of use.  Which it seems I finally reached.

I almost have the engine off the frame, and have reviewed the John Deere technical manual for this machine many times over so that I can do the repair in one afternoon.

My question is this:  after I get the "oil pan/crankcase cover" off to expose the insides of the engine (after removing the water pump first), I have never had to work on the insides of an engine before.  Do I just pull the camshaft straight out, and replace it with the metal one (after lining up timing marks), or do I need to take the valves and springs and heads off to be able to pull out the camshaft.  I only ask because there is one video on youtube from a fellow who replaced his, but he doesn't show how he got the cam gear out.  Ebay sells a cam gear replacement kit, and the fellow sells many other items such as tappets, governor arms, springs, along with the camshaft.  

I understand that I must be careful with the current governor arm but it shouldn't break with good care.

Please let me know if it is a straight forward pull out the bad gear or I need to disassemble any kind of valves/springs/heads.

Thanks for your time.

Answer
Hi Vincent

here is web site for service manual download
http://www.smallenginewarehouse.com/images/manuals/FD620_Service_Manual.pdf

I would replace  the push rods for both cylinders as they are related to the job you are doing  along  with the rockers  

once you have drained coolant and oil , and removed engine from chassis , undo the crankcase coverfs plate bolts , note their positions and lengths  and remove cover plate from case carefully, do not pry on flat surfaces  , use a plastic mallett and tap  @ pry points  

you should not have to disturb cyl heads  if you know nothing is wrong with them
if it aint broke dont fix it rule !

once cover is removed, turn crankshaft untill  crank pinion and camshaft gear marks line up ,  remove  rocker covers and push rods and rocker assys ( mark them so you can put back where you got them from )  ie  cyl  1  in / ex  etc , turn the engine upside down so that the camshaft followers wont fall out  and remove the camshaft assy by pulling it out ( make a note of any shims and try not to remove or disturb any alignment or engagement of any other timmed gears in the crankcase ) replace camshaft and align marks as noted before removal, pull the  crankcase  cover oil seal  , clean cover and fit dowl pins make sure governor shaft / paddle on the crankcase is turned all the way clockwise  and reseal crankcase cover with good quality engine liquid gasket sealer , fit cover making sure gov gear and oil pump and water pump gears all engage before tightening bolts  , replace seal removed in the case cover and refit rocker shafts and push rods from where you got them and set tappetts as per service manual  specs , replace oil filter and oil , turn engine over by hand  to check everything related to valve timming is still good and no binding , - fit rocker covers adjust governor as per service manual on page 23   and reinstall engine to chassis and refit all components removed
finish installation   and check for start run , check for leaks , recheck oil levels  

hope this helps   always refer to service manuals for settings etc

cheers paul